Meya anapofuzwa na Gedi kuwa Siki amekuja kumwona anajizungumzia Asema Siki alipokwenda kumwona awali alimletea bahati mbaya Ukurasa 10


Ofisini pake kabla ya Bili kuingia Meya anajizungumzia Ukurasa 24 Namna anapanga kumtumia mwanakandarasi wa awali na asema hata mwanakandarasi akishtaki ni bure


Baada ya Siki kuongea na simu anajizungumzia Ukurasa 34  Aonyesha msimamo wake kuhusu hali katika baraza la Cheneo Pia dhiki inayowakumba wafanyakazi mfano njaa na magonjwa


Baada ya mazungumzo baina ya Meya na Diwani III Meya anajizungumzia anarudia yale maneno ambayo Diwani III alimwambia kuhusu haja ya kuwasikiliza wafanyakazi Hatimaye anaamua kukutana na uongozi wa wafanyakazi


UCHESHI


Unafanyia tashtiti udhalimu wa Meya na Dida anapoigiza askari Let rat Let rat Let rat Badala ya Left right Left right Haya yanamkejeli Meya


KUCHANGANYA NDIMI


Gedi ana mazoea ya kumjibu Meya Yes sir Hizi ni athari za kikoloni


Bili anamhimiza Meya kuwa na Gentlemans Agreement na yule mwanakandarasi ili amegewe kiasi fulani cha fidia Ukurasa 29


Diwani III asema kuwa kuna Mayors Act ambayo anaweza kutumia kumkandamiza kila mtu Vile vile kuna Riot Act


Meya amtuma Gedi amletee soda katika fridge Ukurasa 17


Meya asema kuna vijana wamehitimu vyuo vikuu fresh kabisa na hawana kazi hata ya utopasi Ukurasa 21


Meya amwambia Bili kuwa ana Entertainment Vote yangoja ualishi tu Ukurasa 27


Ikiwa hii si insurbodination ni nini Ukurasa 55 Meya akimtisha Diwani III kwa kutokubaliana naye


Diwani II adai walipwe overtime Ukurasa 61 na pesa zinapokosekana wanapendekeza kuuzwa kwa fimbo ya Meya


Katika mpango wa kuiba na kuuza fimbo ya Meya Diwani II asema kuwa mpango waliozua ni foolproof Ukurasa 62


Meya asema hana pingamizi kwa kuwa ni grand idea Ukurasa 62


Siki anasema Oh yes kisha kwa mama mwenye mtoto utamfuata sista hapa hadi kwenye wadi ya watoto Ukurasa 5


Meya amwambia Gedi kuwa Siki alione nyumba yake paa AlrightUkurasa 15


Meya asema ameuza viwanja vitatu na amebakisha vitanoIncaseUkurasa 27 Hasa ile prime plot


Amen wanavyoitika Meya na mhubiri wanapoomba


KUHAMISHA NDIMI


Waridi anamuuliza daktari What do you think this is Food poisoning Ukurasa 5


UTOHOZI


Meya  mayor


Daktari amwambia mama mwenye mtoto utamfuata sista sister hadi kwenye wadi ward ya watoto Ukurasa 5


Milenia millenium


Meya alihitajiwa aundiwe kamati committee za madiwani


Meya asema uamuzi wa baraza ni demokrasia democracy Ukurasa 22


Meya asema mwanakandarasi ameenda kortini court Ukurasa 28


Meya asema baraza litagharamia petroli petrol ya mhubiri Ukurasa 44


Medi asema wafanyakazi wanaosha vyoo bila glavu gloves Ukurasa 70


Swichi switch  Diwani I asema anabofya simu tu kutoka mbali na kazi inafanyika


SADFA


Matukio mawili kutokea wakati mmoja bila kupangwa au kutarajwa


Mfano


Daktari Siki na Waridi wanaendelea na mazungumzo yao wakati uo huo mama mwenye mtoto mgonjwa anaingia hospitalini


Diwani I na II na III wanaendelea na mazungumzo yao kisha kwa ghafla Meya aingia


Meya na Bili wanaendelea na mazungumzo yao na wakati uo huo sauti za wafanyakazi zinaskika


Meya na mhubiri wanapoomba kwa kelele na jazba askari III na Gedi wanaingia na kuwaamrisha walale chini


Diwani I na II wanaendelea na mazungumzo yao na wakati uo huo Gedi anaingia ghafla na habari kuwa wanahitajika katika makao yao


LAHAJA


Ya mwananti kuuvunda nti Ukurasa 50  Mwananchi kuivunja nchi


Diwani III asema ndiyo yale ya ngome itauumiza naswi tu mumo ngomeni inatuumiza naswi  na sisi


Meya anasema ndo unamaanisha ni Ukurasa 11 Ndo ndiyo


MBINU YA UTATU


Mtoto mgonjwa ana miaka mitatu


Mtoto alikufa akiwa na miaka mitatu


Mtoto alikuja baada ya siku tatu


Kuua ndege watatu kwa jiwe moja


Madiwani ni watatu


Kuna wawakilishi watatu wa wafanyakazi


Dawa zitafika bandarini baada ya siku tatu


Baada ya siku tatu kutoka bandarini dawa zitafika hospitalini


Meya na madiwani wawili wanakamatwa Jumla ya waliokamatwa ni watu


MASWALI YA KUDURUSU


Maswali ya insha


Fafanua mikakati anayotumia Mstahiki Meya ili kuweza kusalia mamlakani alama 20


Eleza matumizi ya mitindo ifuatayo alama 20


Kinaya


Jazanda


Majazi


Sadfa


Fafanua jinsi dhana ya ukoloni mamboleo inavyojitokeza katika tamthilia ya Mstahiki Meya alama 20


Eleza changamoto zinazowakabili Wanacheneoalama 20


Siku ya kufa kwa nyani miti yote hutelezaThibitisha ukweli wa kauli hii ukirejelea tamthilia ya Mstahiki Meya alama 20


Dhihirisha ufaafu wa anwani Mstahiki Meya alama 20


Eleza umuhimu wa wahusika wafuatao katika tamthilia ya Mstahiki Meya


Waridi alama 10


Siki alama 10


Tamthilia ya Mstahiki Meya imesheheni utetezi wa haki kwa mapana na marefu Thibitisha alama 20


b Maswali ya Muktadha


1 Wewe ndiye wa kuniambia Mimi nimekuuliza wewe


a Eleza muktadha wa dondoo hili alama 4


b Ni mambo yepi yaliyosababisha mnenaji na mnenewa


kuwa katika hali waliyoko sasaalama4


c Eleza sifa za mnenaji na mnenewa alama 8


d Fafanua tofauti za sifa kati ya mnenaji na mnenewa


alama 4


2 Kuna mji gani wenye amani na utulivu kama wetu


a Yaweke maneno haya katika muktadha wakealama 4


b Taja mbinu mbili zilizotumika katika dondoo hili alama


c Fafanua maudhui manne yanayoendelezwa kupitia kwa


mnenaji alama 8


d Taja wahusika wengine wawili walio na sifa sawa na mnenewa na utoe sababu alama 4


CHEMISTRY FORM ONE NOTES


Introduction to chemistry


Chemistry is a branch of Science Science is basically the study of living and nonliving things The branch of science that study living things is called Biology The branch of science that study nonliving things is called Physical Science Physical Science is made up of


Physics the study of matter in relation to energy


Chemistry the study of the composition of matter


Chemistry is thus defined as the branch of science that deals with the structure composition properties and behavior of matter


Basic Chemistry involves studying


Statesphases of matter


Matter is anything that has weightmass and occupies spacevolume Naturally there are basically three states of matter


i Solideg soil sand copper metal bucket ice


iiLiquid eg water Petrol ethanolalcohol Mercury liquid metal


iii gas eg Oxygen Nitrogen Water vapour


A solid is made up of particles which are very closely packed It thus has a definitefixed shape and fixeddefinite volume occupies definite space It has a very high density


A liquid is made up of particles which have some degree of freedom It thus has no definitefixed shape It takes the shape of the container it is put A liquid has fixeddefinite volumeoccupies definite space


A gas is made up of particles free from each other It thus has no definitefixed shape It takes the shape of the container it is put It has no fixeddefinite volumeoccupies every space in a container


b Separation of mixture


A mixture is a combination of two or more substances that can be separated by physical means Simple methods of separating mixtures at basic chemistry level include


i Sortingpickingthis involve physically picking one pure substance from a mixture with anotherother e g sorting maize from maize beans mixture


ii Decantationthis involve pouring out a liquid from a solid that has settled sinking solid in it e g Decanting water forms sand


iiiFiltrationthis involves sieving passing particles of a mixture through a filter containing small holes that allow smaller particle to pass through but do not allow bigger particle to pass through


iv Skimmingthis involve scooping floating particles Eg cream from milk


c Metals and nonmetals


Metals are shiny ductileable to form wires malleableable to form sheet and coil without breaking Eg Iron gold silver copper Mercury is the only liquid metal known


Nonmetals are dull not ductile do not form wires not malleable do not form sheet and break on coilingbrittle Eg Charcoal Sulphur plastics


d Conductors and nonconductors


A conductor is a solid that allow electric current to pass through A nonconductor is a solid that do not allow electric current to pass through


All metals conduct electricity All nonmetals do not conduct electricity except carbon graphite


e Drugs


A drug is a natural or syntheticmanmade substance that when taken changesalter the body functioning A natural or syntheticmanmade substance that when taken changesalter the abnormal body functioning to normal is called medicine Medicines are thus drugs intended to correct abnormal body functions  Medicines should therefore be taken on prescription and dosage


A prescription is a medical instruction to a patientsick on the correct type of medicine to take and periodtime between one intake to the other


A dosage is the correct quantity of drug required to alter the abnormal body function back to normal This is called treatment It is the professional work of qualified doctorspharmacists to administer correct prescription and dosage of drugsmedicine to the sick Prescription and dosage of drugsmedicine to the sick use medical language


Example


i 2 x 4  means 2 tablets for solid drugsspoonfuls for liquid drugs taken 4 times for a duration of one day24 hours and then repeated and continued until all the drug given is finished


ii 1 x 2  means 1 tablets for solid drugsspoonfuls for liquid drugs taken 2 times for a duration of one day24 hours and then repeated and continued until all the drug given is finished


Some drugs need minimal prescription and thus are available without pharmacist doctors prescription They are called Over The Counter OTC drugs OTC drugs used to treat mild headaches stomach upsets common cold include


i Painkillers


ii Antiacids


iii coldflu drugs


All medicine requires correct intake dosage When a prescription dosage is not followed this is called drug misuseabuse Some drugs are used for other purposes other than that intended This is called drug abuse


Drug abuse is when a drug is intentionally used to alter the normal functioning of the body The intentional abnormal function of the drug is to make the victim have false feeling of well being The victim lack both mental and physical coordination


Some drugs that induce a false feeling of well being are illegal They include heroin cocaine bhang Mandrax and morphine


Some abused drugs which are not illegal include Miraa alcohol tobacco sleeping pills


The role of chemistry in society


a Chemistry is used in the following


i Washingcleaning with soap


Washingcleaning is a chemical process that involves interaction of water soap and dirt so as to remove the dirt from a garment


ii Understanding chemicals of life


Living thing grow respire and feed The formation and growth of cells involve chemical processes in living things using carbohydrates proteins and vitamins


iii Baking


Adding baking powder to dough and then heating in an oven involves interactions that require understanding of chemistry


iv Medicine


Discovery test prescription and dosage of drugs to be used for medicinal purposes require advanced understanding of chemistry


v Fractional distillation of crude oil


Crude oil is fractional distilled to useful portions like petrol diesel kerosene by applying chemistry


vi Manufacture of synthetic compoundssubstances


Large amounts of plastics glass fertilizers insecticides soaps cements are manufactured worldwide Advanced understanding of the chemical processes involved is a requirement


vii Diagnosistest for abnormal body functions


If the body is not functioning normally it is said to be sickill Laboratory test are done to diagnose the illnesssickness


b The following career fields require Chemistry as one of subject areas of advancedspecialized study


i Chemical engineeringchemical engineer


ii Veterinary medicineVeterinary doctor


iii MedicineMedical doctorpharmacistnurse


iv BeautyBeautician


v TeachingChemistry teacher


The School Chemistry Laboratory


Chemistry is studied mainly in a science room called a school chemistry laboratory The room is better ventilated than normal classroom It has electricity gas and water taps A school chemistry laboratory has a qualified professional whose called Laboratory technicianassistant


All students user in a school chemistry laboratory must consult the Laboratory technicianassistant for all their laboratory work A school chemistry laboratory has chemicals and apparatus


A chemical is a substance whose composition is known All chemical are thus labeled as they are This is because whereas physically a substance may appear similar chemically they may be different


All Chemicals which are not labeled should never be used Some chemicals are toxicpoisonous explosive corrosive caustic irritants flammable oxidizing carcinogenic or radioactive


Care should always be taken when handling any chemical which have any of the above characteristic properties


Common school chemistry laboratory chemicals include


i Distilled water


ii Concentrated mineral acid which are very corrosive on contact with skin they cause painful open wounds


iii Concentrated alkalibases which are caustic on contact with skin they cause painful blisters


iv Very many types of salts


The following safety guideline rules should be followed by chemistry laboratory users


i Enter the laboratory with permission in an orderly manner without rushingpushingscrabbling


ii Do not try unauthorized experiments They may produce flammable explosive or toxic substances that affect your health


iii Do not taste any chemical in the laboratory They may be poisonous


iv Waft gas fumes to your nose with your palm Do not inhalesmell gases directly They may be highly poisonoustoxic


v Boil substances with mouth of the test tube facing away from others and yourself Boiling liquids spurt out portions of the hot liquid Products of heating solids may be a highly poisonoustoxic gas


vi Wash with lots of water any skin contact with chemicals immediately Report immediately to teacherlaboratory technician any irritation cut burn bruise or feelings arising from laboratory work


vii Read and follow safety instruction All experiments that evolveproduce poisonous gases should be done in the open or in a fume chamber


viii Clean your laboratory work station after use Wash your hand before leaving the chemistry laboratory


ix In case of fire remain calm switch of the source of fuelgas tap Leave the laboratory through the emergency door Use fire extinguishers near the chemistry laboratory to put of medium fires Leave strong fires wholly to professional fire fighters


x Do not carry unauthorized item from a chemistry laboratory


An apparator apparatus are scientific toolsequipment used in performing scientific experiments The conventional apparator used in performing scientific experiments is called standard apparatorapparatus If the conventional standard apparatorapparatus is not available an improvised apparatorapparatus may be used in performing scientific experiments An improvised apparatorapparatus is one used in performing a scientific experiment for a standard apparatorapparatus Most standard apparatus in a school chemistry laboratory are made of glass because


iGlass is transparent and thus reactions interactions inside are clearly visible from outside


ii Glass is comparatively cheaper which reduces cost of equipping the school chemistry laboratory


iii Glass is comparatively easy to cleanwash after use iv Glass is comparatively unreactive to many chemicals


Apparatus are designed for the purpose they are intended in a school chemistry laboratory


Apparatus for measuring volume


1 Measuring cylinder


Measuring cylinders are apparatus used to measure volume of liquid solutions They are calibrated graduated to measure any volume required to the maximum Measuring cylinders are named according to the maximum calibratedgraduated volume eg


10ml measuring cylinder is can hold maximum calibratedgraduated volume of 10mililitres 10 cubic centimetres


50ml measuring cylinder is can hold maximum calibratedgraduated volume of 50mililitres 50 cubic centimetres


250ml measuring cylinder is can hold maximum calibratedgraduated volume of 250mililitres 250 cubic centimetres


1000ml measuring cylinder is can hold maximum calibratedgraduated volume of 1000mililitres 1000 cubic centimetres


2 Burette


Burette is a long and narrowthin apparatus used to measure small accurate and exact volumes of a liquid solution It must be clamped first on a stand before being used It has a tap to run out the required amount out They are calibrated graduated to run out small volume required to the maximum 50ml50cm3


The maximum 50ml50cm3 calibration graduation reading is at the bottom This ensure the amount run out from a tap below can be determined directly from burette reading before and after during volumetric analysis


Burettes are expensive and care should be taken when using them


3 i Pipette


Pipette is a long and narrowthin apparatus that widens at the middle used to measure and transfer small very accurateexact volumes of a liquid solution


It is open on either ends


The maximum 25ml25cm3 calibration graduation mark is a visible ring on one thin end


To fill a pipette to this mark the user must suck up a liquid solution upto a level above the mark then adjust to the mark using a finger


This requires practice


ii Pipette filler


Pipette filler is used to suck in a liquid solution into a pipette instead of using the mouth It has a suck adjust and eject button for ensuring the exact volume is attained This requires practice


4 Volumetric flask


A volumetric flask is thin narrow but widens at the basebottom It is used to measure very accurateexact volumes of a liquid solution


The maximum calibration  graduation mark is a visible ring


Volumetric flasks are named according to the maximum calibratedgraduated volume eg


250ml volumetric flask has a calibratedgraduated mark at exact volume of 250mililitres 250centimetres


1l volumetric flask has a calibratedgraduated mark at exact volume of one litre 1000 cubic centimeters


2l volumetric flask has a calibratedgraduated mark at exact volume of two litres 2000 cubic centimeters


5 Dropperteat pipette


A dropperteat pipette is a long thinnarrow glassrubber apparatus that has a flexible rubber head


A dropperteat pipette is used to measure very small amount drops of liquid solution by pressing the flexible rubber head The numbers of drops needed are counted by pressing the rubber gently at a time


bApparatus for measuring mass


1 Beam balance


A beam balance has a pan where a substance of unknown mass is placed The scales on the opposite end are adjusted to balance with the mass of the unknown substance The mass from a beam balance is in grams


2 Electronicelectric balance


An electronicelectric balance has a pan where a substance of unknown mass is placed The mass of the unknown substance in grams is available immediately on the screen


cApparatus for measuring temperature


A thermometer has alcohol or mercury trapped in a bulb with a thin enclosed outlet for the alcoholmercury in the bulb


If temperature rises in the bulb the alcohol mercury expand along the thin narrow enclosed outlet


The higher the temperature the more the expansion


Outside a calibration graduation correspond to this expansion and thus changes in temperature


A thermometer therefore determines the temperature when the bulb is fully dipped in to the substance being tested To determine the temperature of solid is thus very difficult


dApparatus for measuring time


The stop watchclock is the standard apparatus for measuring time Time is measured using hours minutes and second


Common school stop watchclock has start stop and reset button for determining time for a chemical reaction This requires practice


e Apparatus for scooping


1 Spatula


A spatula is used to scoop solids which do not require accurate measurement Both ends of the spatula can be used at a time


A solid scooped to the brim is one spatula end full A solid scooped to half brim is half spatula end full


2 Deflagrating spoon


A deflagrating spoon is used to scoop solids which do not require accurate measurement mainly for heating Unlike a spatula a deflagrating spoon is longer


f Apparatus for putting liquidssolid for heating


1 Test tube


A test tube is a narrowthin glass apparatus open on one side The end of the opening is commonly called the the mouth of the test tube


2 Boilingignition tube


A boilingignition tube is a wide glass apparatus than a test tube open on one side The end of the opening is commonly called the the mouth of the boilingignition tube


3 Beaker


Beaker is a wide calibratedgraduated lipped glassplastic apparatus used for transferring liquid solution which do not normally require very accurate measurements


Beakers are named according to the maximum calibratedgraduated volume they can hold eg


250ml beaker has a maximum calibratedgraduated volume of 250mililitres 250 cubic centimeters


1l beaker has a maximum calibratedgraduated volume of one litre 1000 cubic centimeters


5 l beaker has a maximum calibratedgraduated volume of two litres 2000 cubic centimeters


4 Conical flask


A conical flask is a moderately narrow glass apparatus with a wide base and no calibrationgraduation Conical flasks thus carryhold exact volumes of liquids that have been measured using other apparatus It can also be put some solids The narrow mouth ensures no spillage


Conical flasks are named according to the maximum volume they can hold eg 250ml Conical flasks hold a maximum volume of 250mililitres 250 cubic centimeters


500ml Conical flasks hold a maximum volume of 500ml 1000 cubic centimeters


5 Round bottomed flask


A round bottomed flask is a moderately narrow glass apparatus with a wide round base and no calibrationgraduation Round bottomed flask thus carryhold exact volumes of liquids that have been measured using other apparatus The narrowthin mouth prevents spillage The flask can also hold weighed solids A round bottomed flask must be held clamped when in use because of its wide narrow base


6 Flat bottomed flask


A flat bottomed flask is a moderately narrow glass apparatus with a wide round base with a small flat bottom It has no calibrationgraduation


Flat bottomed flasks thus carryhold exact volumes of liquids that have been measured using other apparatus The narrowthin mouth prevents spirage They can also hold weighed solids A flat bottomed flask must be held clamped when in use because its flat narrow base is not stable


g Apparatus for holding unstable apparatus during heating


1 Tripod stand


A tripod stand is a three legged metallic apparatus which unstable apparatus are placed on during heatingBeakers Conical flasks round bottomed flask and flat bottomed flasks are placed on top of tripod stand during heating


2 Wire gauzemesh


Wire gauzemesh is a metalliciron plate of wires crossings It is placed on top of a tripod stand


i Ensure even distribution of heat to prevent cracking glass apparatus


ii Hold smaller apparatus that cannot reach the edges of tripod stand


3 Clamp stand


A clamp stand is a metallic apparatus which tightly hold apparatus at their neck firmly


A clamp stand has a wide metallic base that ensures maximum stability The height and position of clamping is variable This require practice


4 Test tube holder


A test tube holder is a hand held metallic apparatus which tightly hold testboilingignition tube at their neck firmly on the other end


Some test tube holders have wooden handle that prevent heat conduction to the hand during heating


5 Pair of tong


A pair of tong is a scissorlike hand held metallic apparatus which tightly hold firmly a small solid sample on the other end


6 Gas jar


A gas jar is a long wide glass apparatus with a wide base


It is open on one end It is used to collectput gases


This requires practice


h Apparatus for holdingdirecting liquid solutionsfunnels to avoid spillage


1 Filter funnel


A filter funnel is a wide mouthed mainly plastic apparatus that narrow drastically at the bottom to a long extension


When the long extension is placed on top of another apparatus a liquid solution can safely be directed through the wide mouth of the filter funnel into the apparatus without spirage


Filter funnel is also used to place a filter paper during filtration


2 Thistle funnel


A thistle funnel is a wide mouthed glass apparatus that narrow drastically at the bottom to a very long extension


The long extension is usually drilled through a stoppercork


A liquid solution can thus be directed into a stoppered container without spillage


3 Dropping funnel


A dropping funnel is a wide mouthed glass apparatus with a tap that narrow drastically at the bottom to a very long extension


A liquid solution can thus be directed into a stoppered container without spillage at the rate determined by adjusting the tap


4 Separating funnel


A separating funnel is a wide mouthed glass apparatus with a tap at the bottom narrow extension


A liquid solution can thus be directed into a separating funnel without spillage It can also safely be removed from the funnel by opening the tap


It is used to separate two or more liquid solution mixtures that form layersimmiscible This requires practice


h Apparatus for heatingBurners


1 Candle spirit burner kerosene stove charcoal burnerjiko are some apparatus that can be used for heating


Any flammable fuel when put in a container and ignited can produce some heat


2 Bunsen burner


The Bunsen burner is the standard apparatus for heating in a Chemistry school laboratory


It was discovered by the German Scientist Robert Wilhelm Bunsen in1854


aDiagram of a Bunsen burner


A Bunsen burner uses butanelaboratory gas as the fuel The butanelaboratory gas is highly flammable and thus usually stored safely in a secure chamber outside Chemistry school laboratory It is tapped and distributed into the laboratory through gas pipes


The gas pipes end at the gas tap on a chemistry laboratory bench If opened the gas tap releases butanelaboratory gas Butanelaboratory gas has a characteristic odorsmell that alerts leakagesopen gas tap


The Bunsen burner is fixed to the gas tap using a strong rubber tube


The Bunsen burner is made up of the following parts


i Base plate to ensure the burner can stand on its own


iiJeta hole through which laboratory gas enters the burner


iiiCollarsleeveadjustable circular metal attached to the main chimneyburell with a side holeentry It controls the amount of air entering used during burning


ivAir hole a holeentry formed when the collar side hole is in line with chimney side hole If the collar side hole is not in line with chimney side hole the air hole is said to be closed If the collar side hole is in line with chimney side hole the air hole is said to be open


vChimney tall round metallic rod attached to the base plate


bProcedure for lightingigniting a Bunsen burner


1 Adjust the collar to ensure the air holes are closed


2 Connect the burner to the gas tap using a rubber tubing Ensure the rubber tubing has no side leaks


3 Turn on the gas tap


4 Ignite the top of the chimney using a lighted match stickgas lighterwooden splint


5 Do not delay excessively procedure iv from iii to prevent highly flammable laboratory gas from escapingleaking


cBunsen burner flames


A Bunsen burner produces two types of flames depending on the amount of air entering through the air holes


If the air holes are fully open a non luminous flame is produced If the air holes are fully closed a luminous flame is produced If the air holes are partially open closed a hybrid of non luminous and luminous flames is produced


Characteristic differences between luminous and nonluminous flame


Scientific apparatus are drawn


i Using a proportional two dimension 2D crosssections Three dimensions 3D are not recommended


ii Straight edges of the apparatus on a scientific diagram should be drawn using ruler


iii Curved edges of the apparatus on a scientific diagram should be drawn using free hand


ivThe bench tripod or clamp to support apparatus which cannot stand on their own should be shown


CLASSIFICATION OF SUBSTANCES


Substances are either pure or impure A pure substance is one which contains only one substance


An impure substance is one which contains two or more substances A pure substance is made up of a pure solid pure liquid or pure gas


A mixture is a combination of two or more pure substances which can be separated by physical means The three states of matter in nature appear mainly as mixtures of one with the other


Common mixtures include


aSolutionssolidliquid dissolved mixture


Experiment


To make a solution of copper II sulphate VIPotassium magnateVII sodium chloride


Procedure


Put about 100 cm3 of water in three separate beakers Separately place a half spatula end full of copper II sulphate VI Potassium manganate VII and sodium chloride crystals to each beaker Stir for about two minutes


Observation


Copper II sulphate VI crystals dissolve to form a blue solution


Potassium manganate VII crystals dissolve to form a purple solution


Sodium chloride crystals dissolve to form a colourless solution


Explanation


Some solids liquids and gases dissolve in some other liquids


A substanceliquid in which another substance dissolves is called solvent


A substance solid gas which dissolves in a solvent is called solute


When a solute dissolves in a solvent it forms a uniform mixture called solution


A solute dissolved in water as the solvent exists in another state of matter called aqueous state Water is referred as the universal solvent because it dissolves many solutes A solute that dissolves in a solvent is said to be soluble Soluble particles uniformly spread between the particles of watersolvent and cannot be seen


Solute  Solvent  solution


Solute  Water  aqueous solution of solute


The solute dissolved in water gives the name of the solution e g


1 Sodium chloride solution is a solution formed after dissolving sodium chloride crystalssolid in water Sodium chloride exists in aqueous state after dissolving


Sodium chloride  Water  Sodium chloride solution


NaCls  aq  NaClaq


2 Ammonia solution is a solution formed after dissolving ammonia gas in water Ammonia exists in aqueous state after dissolving


Ammonia gas  Water  aqueous ammonia


NH3 g  aq  NH3 aq


3 Copper II sulphate VI solution is a solution formed after dissolving Copper II sulphate VI crystalssolid in water Copper II sulphate VI exists in aqueous state after dissolving


Copper II sulphate VI  Water  Copper II sulphate VI solution


CuSO4s  aq  CuSO4 aq


4 Potassium manganateVII solution is a solution formed after dissolving Potassium manganateVII crystalssolid in water


Potassium manganateVIIexist in aqueous state after dissolving


Potassium manganateVII  Water  Potassium manganateVII solution


KMnO4s  aq  KMnO4 aq


bSuspension precipitatessolidliquid mixture which do not dissolve


Experiment To make soil flour and Lead II Iodide suspensionprecipitate


Procedure


Put about 100 cm3 of water in three separate beakers Separately place a half spatula end full of soil maize and lead II Iodide to each beaker Stir for about two minutes


Observation


Some soil maize and lead II Iodide float in the water


A brown suspensionprecipitateparticles suspended in water containing soil


A white suspensionprecipitateparticles suspended in water containing flour


A yellow suspensionprecipitateparticles suspended in water containing Lead II iodide Some soil maize and lead II Iodide settle at the bottom after some time


Explanation


Some solid substances do not dissolve in a liquid They are said to be insoluble in the solvent When an insoluble solid is put in liquid


i Some particles remain suspendedfloating in the liquid to form a suspension precipitate


ii Some particles sinksettle to the bottom to form sediments after being allowed to stand


An insoluble solid acquire the colour of the suspensionprecipitate eg


1 A white suspension precipitate have some fine white particles suspended floating in the liquid Not white solution


2 A blue suspension precipitate has some fine blue particles suspended floating in the liquid


3 A green suspension precipitate has some fine green particles suspended floating in the liquid


4 A brown suspension precipitate has some fine brown particles suspended floating in the liquid


4 A yellow suspension precipitate has some fine yellow particles suspended floating in the liquid


c i Miscibles Liquidliquid mixtures


To form waterethanol and Keroseneturpentine miscibles


Procedure


iMeasure 50cm3 of ethanol into 100cm3 beaker Measure 50cm3 of water Place the water into the beaker containing ethanol Swirl for about one minute


iiMeasure 50cm3 of kerosene into 100cm3 beaker Measure 50cm3 of turpentine oil Place the turpentine oil into the beaker containing kerosene Swirl for about one minute


Observation


Two liquids do not form layers


Ethanol and water form a uniform mixture


Kerosene and turpentine oil form uniform mixture


Explanation


Ethanol is miscible in Water Kerosene is miscible in turpentine oil Miscible mixture form uniform mixture They do not form layers The particles of one liquid are smaller than the particles of the other The smaller particles occupy the spaces between the bigger particles


Immiscibles Liquidliquid mixtures


To form waterturpentine oil and Kerosenewater miscibles


iMeasure 50cm3 of water into 100cm3 beaker Measure 50cm3 of turpentine oil Place the oil into the beaker containing water Swirl for about one minute


ii Measure 50cm3 of water into 100cm3 beaker Measure 50cm3 of kerosene Place the kerosene into the beaker containing water Swirl for about one minute


Two liquids form layers


Turpentine and water do not form a uniform mixture


Water and kerosene do not form uniform mixture


Kerosene is immiscible in Water Water is immiscible in turpentine oil Immiscible mixtures do not form uniform mixtures They form layers The size of the particles of one liquid is almost equal to the particles of the other The particles of one liquid cannot occupy the spaces between the particles of the other The heavier particles settle at the bottom The less dense particles settle on top


dSolidsolid mixturesAlloys


Before solidifying some heated moltenliquid metals dissolve in another metal to form a uniform mixture of the two On solidifying a uniform mixture of the metals is formed A uniform mixture of two metals on solidifying is called alloy In the alloy one metallic particle occupies the spaces between the metallic particles of the other


c Common alloys of metal


METHODS OF SEPARATING MIXTURES


Mixtures can be separated from applying the following methods


a Decantation


Sediments can be separated from a liquid by pouring out the liquid This process is called decantation


Experiment


Put some sand in a beaker Add about 200cm3 of water Allow sand to settle Pour off water carefully into another beaker


Observation


Sand settles at the bottom as sediments


Less clean water is poured out


Explanation


Sand does not dissolve in water Sand is denser than water and thus settles at the bottom as sediment When poured out the less dense water flows out


bFiltration


Decantation leaves suspended particles in the liquid after separation Filtration is thus improved decantationFiltration is the method of separating insoluble mixturesparticlessolids from a liquid


Experiment To separate soil and water using filtration


Fold a filter paper to fit well into a filter funnel Place the funnel in an empty 250 cm3 beaker


Put one spatula end full of soil into 50cm3 of water Stir Put the soilwater mixture into the filter funnel


Observations


Clean water is collected below the filter funnel


Soil remains above the filter paper


A filter paper is porous which act like a fine sieve with very small holes The holes allow smaller water particles to pass through but do not allow bigger soil particles The liquid which passes through is called filtrate The solid which do not pass through is called residue


Set up of apparatus


In industries filtration is used in engine filters to clean up air


cEvaporation


Evaporation is a method of separating a solutesolid from its solution This involves heating a solution solvent and soluteto vapourize the solvent out of the solution mixture leaving pure solutesolid If a mixture contain insoluble solid they are filtered out


Experiment To separate a mixture of soil and salt sodium chloride


Procedure


Put one spatula end full of soil on a filter paper


Put one spatula full of common saltsodium chloride into the same filter paper Mix well using the spatula


Place about 200cm3 of water into a beaker


Put the contents of the filter paper into the water Stir thoroughly using a glassstirring rod for about one minute


Fold a filter paper into a filter funnel


Pour half portion of the contents in the beaker into the filter funnel


Put the filtrate into an evaporating dish Heat on a water bath


Observation


iOn mixing


Colourless crystals and brown soil particles appear on the filter paper


iiOn adding water


Common soil dissolves in water Soil particles do not dissolve in water


iiiOn filtration


Colourless liquid collected as filtrate below the filter funnelpaper


Brown residue collected above the filter funnelpaper


ivOn evaporation


Colourless crystals collected after evaporation


Explanation


Solid mixture of sand and common salt take the colors of the two


On adding water common salt dissolves to form a solution


Soil does not because it is insoluble in water and thus forms a suspension


On filtration a residue of insoluble soil does not pass through the filter paper


It is collected as residue


Common salt solution is collected as filtrate


On heating the filtrate the solventwater evaporatevaporize out of the evaporating dish leaving common salt crystals


Vapourizationevaporation can take place even without heating


This is the principleprocess of drying wet clothes on the hanging line


Set up of apparatus


d Distillation


Distillation is an improved evaporation where both the solute and the solvent in the solution are separated collected Distillation therefore is the process of separating a solution into constituent solid solute and the solvent It involves heating the solution to evaporatevaporize the solvent out The solvent vapour is then condensed back to a liquid


Experiment To obtain copper II sulphate VI crystals and water from copper II sulphate VI solution


Procedure


Put one spatula end full of copper II sulphate VI crystals into a 250cm3 beaker


Place about 200cm3 of water into the beaker


Stir thoroughly using a glassstirring rod for about one minute


Pour half portion of the contents in the beaker into a round bottomedflatconical flask broken porcelainsandglass into the flask


Put a few pieces of b Stopper the flask


Connect the flask to a Liebig condenser using delivery tube


Place a 200cm3 clean empty beakerconical flask as a receiver at the end of the Liebig condenser


Circulate water in the Liebig condenser


Heat the flask strongly on a tripod stand with wire meshgauze until there is no more visible boiling bubbles in the flask


Observation


Copper II sulphate VI crystals dissolve in water to form a blue solution On heating colourless liquid is collected in the receiver


Blue crystals are left in the flask


If gently heated further the blue crystals turn to white powder


Explanation


On heating blue Copper II sulphate VI solution the colourless liquid solvents evaporatevaporize


The liquid vapourgas passes through the delivery tube to the Liebig condenser


The Liebig condenser has a cold water inlet near the receiver and cold water out let


This ensures efficient cooling If the cold water outletinlet is reversed the water circulation would be less efficient


The water in the receiver would be warm In the Liebig condenser the cold water condenses the liquid vapour into liquid


The condensed liquid collects in the receiver as distillate


The solute of blue Copper II sulphate VI crystals is left in the flask as residue


During simple distillation therefore the solution is heated to vaporize evaporate the solventone component which is condensed at a different part of the apparatus


The purpose of pieces of broken porcelainporous potglasssand is to


i Prevent bumping of the solution during boiling


ii Ensure smooth and even boiling


Salty sea water can be made pure through simple distillation


Any mixture with a large difference 40oC in boiling point can be separated using simple distillation


Set up of apparatus


eFractional distillation


Fractional distillation is an improved simple distillation used specifically to separate miscible mixtures with very close near boiling points


Fractional distillation involves


i Heating the mixture in a conicalround bottomed flat bottomed flask


The pure substance with a lower boiling point and thus more volatile evaporatesboilsvaporize firsteg Pure ethanol has a boiling point of 78oCPure water has a boiling point of 100 oC at sea levelone atmosphere pressure


When a miscible mixture of ethanol and water is heated ethanol vaporizes boils evaporates first because it is more volatile


iiThe conicalround bottomed flat bottomed flask is connected to a long glass tube called fractionating column


The purpose of the fractionating column is to offer areas of condensation for the less volatile pure mixture


The fractionating column is packed with glass beadsbroken glass porcelain shelves to increase the surface area of condensation of the less volatile pure mixture


iiiWhen the vapors rise they condense on the glass beadsbroken glass porcelain  shelves which become hot


When the temperature of the glass beadsbroken glassporcelainshelves is beyond the boiling point of the less volatile pure substance the pure substance rise and condensation take place on the glass beadsbroken glassporcelainshelves at a higher level on the fractionating column


The less volatile pure substance tricklesdrips back down the fractionating column or back into the conicalround bottomed flat bottomed flask to be heated again eg


If the temperature on glass beadsbroken glassporcelainshelves is beyond 78oC the more volatile pure ethanol rise to condense on the glass beadsbroken glass porcelainshelves higher in the fractionating column


Water condenses and then driptrickle to the glass beadsbroken glass porcelain shelves lower in the fractionating column because it is less volatile


iv The fractionating column is connected to a Liebig condenser The Liebig condenser has a cold water inlet and outlet circulation


The more volatile mixture that reach the top of the fractionating column is condenses by the Liebig condenser into a receiver It is collected as the first fraction


vAt the top of the fractionating column a thermometer is placed to notemonitor the temperature of the boiling mixtures


Pure substances have constantfixed boiling point When one mixture is completely separated the thermometer reading rises


Eg the thermometer reading remains at78oC when ethanol is being separated When no more ethanol is being separated the mercuryalcohol level in the thermometer rises


viThe second subsequent fractions are collected in the receiver after noting a rise the mercuryalcohol level in the thermometer


Eg the thermometer reading rises to 100oC when water is being separated It is passed through the Liebig condenser with the cold water inlet and outlet circulation It is collected different receiver as the secondsubsequent fraction


viiEach fraction collected should be confirmed from known physicalchemical propertiescharacteristic


Example


Ethanol


Ethanol is a colourless liquid that has a characteristic smell When it is put in a watch glass then ignited it catches fire and burn with a blue flame


Water


Water is a colourless liquid that has no smellodour When it is put in a watch glass then ignited it does not catch fire


Set up of apparatus


Industrial application of Fractional distillation


On a large scalefractional distillation is used


iIn fractional distillation of crude oil in an oil refinery


Crude oil is a mixture of many fractions When heated in a furnace the different fractions separate out according to their boiling point In Kenyafractional distillation takes place at Changamwe in Mombasa


iiIn fractional distillation of air


Air contain a mixture of three main useful gases which are condensed by cooling to very low temperature 200oC to form a liquid The liquid is then heated Nitrogen is the most volatile 196 oC and thus comes out as the first fraction Argon at 186 oC is the second fraction Oxygen  at 183 oC is the last fraction The three gases are very useful industrial gases


fSeparation of immiscibles Using a separating funnel


Two or more liquids that form layers on mixing are immiscible Immiscible mixture arrange themselves according to their densities


ie The denser liquid sink to the bottom The less dense liquid floats on the denser one Immicible mixtures can be separated from each other by using a separating funnel


Experiment To separate an immiscible mixture of paraffin and water


Procedure


Place about 100cm3 of water into a 250cm3 beaker Add about 100cm3 of paraffin into the beaker Stir


Transfer the mixture into a separating funnel Allow to settle for about one minute Open the tap run out the lower layer out slowly into a clean beaker Close the tap when the upper layer is very close to the tap


Run out the intermediate small amount of the mixture near the tap into a beaker Discard it


Run out the remaining upper layer into a fresh beaker


Place a portion of upper and lower layer into a watch glass separately after separating each Ignite


Observation


Water and paraffin are both colourless liquids


Two layers are formed on mixing


Colourless odorless liquid collected first It does not catch fire


A colourless liquid with characteristic smell collected latersecond It catches fire and burn with a yellow smoky flame


Explanation


Water and paraffin are immiscible Water is denser than paraffin When put in a separating funnel paraffin float on water On opening the tap water runs out A mixture of water and paraffin at the junction of the two is discarded It is not pure


Set up of apparatus


gSublimationdeposition


Some solids on heating do not melt to a liquid but change directly to a gas The process by which a solid changes to a gas is called sublimation The gas cools back and changes directly to a solid The process by which a gas changes to a solid is called deposition Sublimation and deposition therefore are the same but opposite processes


Sublimation Deposition


Some common substances that undergo sublimation deposition include


iIodine iiCarbonIVoxide iiiCamphor iv ammonium chloride vIronIIIchloride viAluminumIIIchloride


vii benzoic acid


If a mixture has any of the above as a component then on heating it will change to a gas and be deposited away from the source of heating


Procedure


Place about one spatula full of ammonium chloride crystals into a clean dry 100cm3 beaker Add equal amount of sodium chloride crystals into the beaker Swirl to mix


Place the beaker on a tripod stand


Put about 100cm3 of water into another beaker Place carefully the beaker containing water on top of the beaker containing the solid mixture Lightignite a burner and heat the solid


Observation


iWith ammonium chloridecommon salt mixture


White fumes produced


White sublimate deposited


Colourless residue left


iiWith Iodinecommon salt mixture


Purple fumes produced


Dark grey sublimate deposited


Explanation


iOn heating a mixture of ammonium chloride and common salt a white fume of ammonium chloride is produced The white fumes solidify as white sublimate on the cooler parts Common salt remains as residue


Chemical equation


Ammonium chloride solid Ammonium chloride gas


NH4Cls NH4Clg


iiOn heating a mixture of Iodine and common salt a purple fume of Iodine vapour is produced The purple fumes solidify as dark grey sublimate on the cooler parts Common salt remains as residue


Iodine solid Iodine gas


I2s I2 g


hChromatography


Chromatography is a method of separating components of a solution mixture by passing it through a medium where the different components move at different rates The medium through which the solution mixture is passed is called absorbent material


Paper chromatography is a method of separating colored dyes by using paper as the absorbent material


Since dyes are insolubledo not dissolve in water ethanol and propanone are used as suitable solvents for dissolving the dye


Practically a simple paper chromatography involve placing a dyematerial on the absorbent material adding slowly a suitable soluble solvent on the dyematerial using a dropper the solvent spread out on the absorbent material carrying the soluble dye away from the origin


The spot on which the dye is initiallyoriginally placed is called baseline The farthest point the solvent spread is called solvent front


The farthest a dye can be spread by the solvent depend on


i Density of the dyethe denser the dye the less it spread from the basely ne by the solvent


ii Stickiness of the dyesome dyes sticks on the absorbent material more than other thus do not spread far from baseline


Experiment To investigate the colors in ink


Procedure


Method 1


Place a filter paper on an empty beaker Put a drop of blackblue ink in the centre of the filter paper Wait for about one minute for the ink drop to spread Using a clean teat pipettedropper add one drop of ethanolpropanone Wait for about one minute for the ink drop to spread further Add about twenty other drops of ethanol waiting for about one minute before each addition Allow the filter paper to dry


Method 2


Cut an 8 centimeter thin strip of a filter paper At about 3cm on the strip place a drop of ink Place the filter paper in a 10cm length boiling tube containing 5cm3 of ethanol Ensure the cut strip of the filter paper just dips into the ethanol towards the ink mark Cover the boiling tube Wait for about twenty minutes Remove the boiling tube and allow the filter paper to dry


Set up of apparatus


Explanation


When a drop of ink is placed on an absorbent material it sticks On adding an eluting solvent it dissolves the dye spread out with it The denser and sticky pure dye move least The least densesticky pure dye move farthest A pure dye will produce the same chromatogramspot if the same eluting solvent is used on the same absorbent material Comparing the distance moved by a pure dye with a mixture the coloured dyes in a mixture can be deduced as below


Example 1


The chromatogram of pure dyes A B C and a dye mixture D is shown below Determine the pure dyes present in D On the diagram show


ithe solvent front


ii Baseline


Iii the most soluble pure dye


i Solvent extraction


Solvent extraction is a method of separating oil from nutsseeds Most nuts contain oil First the nuts are crushed to reduce their size and increase the surface area A suitable volatile solvent is added The mixture is filtered The filtrate solvent is then allowed to crystallize leaving the oilfat If a filter paper is rubbedsmeared with the oilfat it becomes translucent This is the test for the presence of oilfat


Experiment To extract oil from Macadamia nut seeds


Crush Macadamia nut seeds form the hard outer cover Place the inner soft seed into a mortar Crush add a little sand to assist in crushing


Add a little propanone and continue crushing Continue crushing and adding a little propanone until there is more liquid mixture than the solid Decantfilter Put the filtrate into an evaporating dish Vapourize the solvent using solar energy sunlight Smearrub a portion of the residue left after evaporation on a clean dry filter paper


Observation Explanation


Propanone dissolve fatoil in the macadamia nuts Propanone is more volatile lower boiling point than oilfat In sunlightsolar energy propanone evaporatevaporize leaving oilfathas a higher boiling pointAny seed like corn wheat  rice soya bean may be used instead of macadamia seed When oilfat is rubbed smeared on an opaque paper it becomes translucent


j Crystallization


Crystallization is the process of using solubility of a solutesolid to obtain the solutesolid crystals from a saturated solution by cooling or heating the solution


A crystal is the smallest regular shaped particle of a solute Every solute has unique shape of its crystals


Some solutions form crystals when heated This is because less solute dissolves at higher temperature Some other solutions form crystals when cooled This is because less solute dissolves at lower temperature


Experiment To crystallize copper II sulphate VI solution


Procedure


Place about one spatula full of hydrated copper sulphate VI crystals into 200cm3 of distilled water in a beaker Stir Continue adding a little more of the hydrated copper sulphate VI crystals and stirring until no more dissolve Decantfilter Cover the filtrate with a filter paper Pierce and make small holes on the filter paper cover Preserve the experiment for about seven days


ObservationExplanation


Large blue crystals formed


When hydrated copper II sulphate crystals are placed in water they dissolve to form copper II sulphate solution After some days water slowly evaporate leaving large crystals of copper II sulphate If the mixture is heated to dryness small crystals are formed


PhysicalTemporary and Chemical changes


A physicaltemporary change is one which no new substance is formed and is reversible back to original


A chemicalpermanent change is one which a new substance is formed and is irreversible back to original


The following experiments illustrates physical and chemical changes


aHeating ice


Place about 10g of pure ice in a beaker Determine its temperature Record it at time 00 in the table below Heat the ice on a strong Bunsen flame and determine its temperature after every 60seconds1minute to complete the table below


Plot a graph of time against Temperature yaxes


Explain the shape of your graph


Meltingfreezingfusionsolidification and boiling vaporization evaporation are the two physical processes


Melting freezing point of pure substances is fixed constant


The boiling point of pure substance depends on external atmospheric pressure


Meltingfusion is the physical change of a solid to liquid


Freezing is the physical change of a liquid to solid


Meltingfreezingfusionsolidification is therefore two opposite but same reversible physical processes ie


A s A l


Boilingvaporizationevaporation is the physical change of a liquid to gas


Condensation liquidification is the physical change of gas to liquid


Boilingvaporizationevaporation and condensation liquidification are therefore two opposite but same reversible physical processes ie


B l Bg


Practically


i Meltingliquidificationfusion involves heating a solid to weaken the strong bonds holding the solid particles together


Solids are made up of very strong bonds holding the particles very close to each other Kinetic Theory of matter


On heating these particles gain energyheat from the surrounding heat source to form a liquid with weaker bonds holding the particles close together but with some degree of freedom


iiFreezingfusionsolidification involves cooling a liquid to reform rejoin the very strong bonds to hold the particles very close to each other as solid and thus lose their degree of freedom Kinetic Theory of matter


Freezing fusion  solidification is an exothermic H process that require particles holding the liquid together to lose energy to the surrounding


iiiBoilingvaporizationevaporation involves heating a liquid to completely breakfree the bonds holding the liquid particles together


Gaseous particles have high degree of freedom Kinetic Theory of matter


Boiling vaporization  evaporation is an endothermic H process that requireabsorb energy from the surrounding


ivCondensationliquidification is reverse process of boiling vaporization  evaporation


It involves gaseous particles losing energy to the surrounding to form a liquid


AIR OXYGEN AND COMBUSTION


ATHE ATMOSPHERE


1 The atmosphere is made up of air Air is a mixture of colourless odorless gases which is felt as wind air in motionAll living things breath in air for respiration Plants use air for respiration and photosynthesis


2 The main gases present in the atmosphereair


3 The following experiments below shows the presence and composition of the gases in airatmosphere


aTo find the composition of air supporting combustion using a candle stick


Procedure


Measure the length of an empty gas jar M1 Place a candle stick on a Petri dish Float it on water in basintrough Cover it with the gas jar Mark the level of the water in the gas jar M2 Remove the gas jar Light the candle sick Carefully cover it with the gas jar Observe for two minutes Mark the new level of the water M3


Set up of apparatus


Sample observations


Candle continues to burn then extinguishedgoes off


Level of water in the gas jar rises after igniting the candle


Length of empty gas jar  M1 14cm


Length of gas jar without water before igniting candle  M2 10 cm


Length of gas jar with water before igniting candle  M1  M2 14 10  4 cm


Length of gas jar with water after igniting candle  M3  8 cm


Length of gas jar without water after igniting candle  M1  M3  10 8  2 cm


Explanation


Candle burns in air In a closed system vessel the candle continues to burn using the part of air that support burningcombustion This is called the active part of air The candle goes offextinguished when all the active part of air is used up The level of the water rises to occupy the space volume occupied by the used active part of air


The experiment is better when very dilute sodiumpotassium hydroxide is used instead of water Dilute Potassium sodium hydroxide absorb Carbon IV oxide gas that comes out from burningcombustion of candle stick


From the experiment above the  composition of the


i Active part of air can be calculated


M2  M3 x 100  10 8 x 100  20


M2 10cm


ii Inactive part of air can be calculated


100 20  80  M3  8 x 100  80


bTo find the composition of active part of air using heated copper turnings


Procedure


Clamp a completely packedfilled open ended glass tube with copper turnings Seal the ends with glasscotton wool


Label two graduated syringes as A and B Push out air from syringe A Pull in air into syringe B


Attach both syringe A and B on opposite ends of the glass tube


Determine and record the volume of air in syringe B V1


Heat the glass tube strongly for about three minutes


Push all the air slowly from syringe B to syringe A as heating continues Push all the air slowly from syringe A back to syringe B and repeatedly back and forth


After about ten minutes determine the new volume of air in syringe B V2


Set up of apparatus


Sample observations


Colour change from brown to black


Volume of air in syringe B before heating V1  1580cm3


Volume of air in syringe B after heating V2  1272cm3


Volume of air in syringe B used by copper V1  V2  308cm3


Sample questions


1 What is the purpose of


i glasscotton wool


To preventstop copper turnings from being blown into the syringeout of the glass tube


ii Passing air through the glass tube repeatedly


To ensure all the active part of air is used up


iii Passing air through the glass tube slowly


To allow enough time of contact between the active part of and the heated copper turnings


2 State and explain the observations made in the glass tube


Brown copper metal reacts with the active part of airoxygen to form black copper II oxide


Chemical equation


Copper  Oxygen  Copper II oxide


2Cus  O2 g  2CuOs


The reaction reduces the amountvolume of oxygen in syringe B leaving the inactive part of air Copper only react with oxygen when heated


3 Calculate the  of


i Active part of air


active part of air  V1  V2 x 100  308cm3 x 100  19493


V1 1580cm3


ii Inactive part of air


Method 1


inactive part of air  V2 x 100 1272cm3 x 100  80506


Method 2


inactive part of air  100  active part of air


100   19493   80507


4 The  of active part of air is theoretically higher than the above while  of inactive part of air is theoretically lower than the above Explain


Not all the active part of air reacted with copper


5 State the main gases that constitute


a active part of air


Oxygen


b Inactive part of air


Nitrogen carbon IV oxide and noble gases


6 If the copper turnings are replaced with magnesium shavings the  of active part of air obtained is extraordinary very high Explain


Magnesium is more reactive than copper The reaction is highly exothermic It generates enough heat for magnesium to react with both oxygen and nitrogen in the air


A white solidash mixture of Magnesium oxide and Magnesium nitride is formed This considerably reduces the volume of air left after the experiment


Chemical equation


Magnesium  Oxygen  magnesium II oxide


2Mgs  O2 g  2MgOs


Magnesium  Nitrogen  magnesium II nitride


3Mgs  N2 g  Mg3N2 s


cTo find the composition of active part of air using alkaline pyrogallol


Procedure


Measure about 2cm3 of dilute sodium hydroxide into a graduated gas jar Record the volume of the graduated cylinder V1


Place about two spatula end full of pyrogallol1 2 3trihydroxobenzene into the gas jar Immediately place a cover slip firmly on the mouth of the gas jar Swirl thoroughly for about two minutes


Invert the gas jar in a troughbasin containing water Measure the volume of air in the gas jar V2


Sample observations


Colour of pyrogallol1 2 3trihydroxobenzene change to brown


Level of water in gas jar rises when inverted in basintrough


Volume of gas jar air in gas jar V1 800cm3


Volume of gas jar air in gas jar after shaking with alkaline pyrogallol1 2 3trihydroxobenzene V2 640 cm3


Sample questions


1 Which gas is absorbed by alkaline pyrogallol123trihydroxobenzene


Oxygen


2 Calculate the


i  of active part of air


V1V2 x 100  800cm3  640 cm3 x 100  20


V1 800cm3


ii  of inactive part of air


V2 x 100  640 cm3 x 100  80


dTo establish the presence of carbon IV oxide in air using lime water


Pass tap water slowly into an empty flask as in the set up below


Sample observation questions


What is the purpose of paper cover


To ensure no air enters into the lime water


What happens when water enters the flask


It forces the air from the flask into the lime water


3 What is observed when the air is bubbled in the lime water


A white precipitate is formed The white precipitate dissolves on prolonged bubbling of air


4 a Identify the compound that form


ilime water


Calcium hydroxide  CaOH2


ii White precipitate


Calcium carbonate CaCO3


iii When the white precipitate dissolves


Calcium hydrogen carbonate CaHCO3


bWrite the chemical equation for the reaction that tale place when


i White precipitate is formed


Calcium hydroxide  carbon IV oxide  Calcium carbonate  water


Ca OH 2aq  CO2 g  CaCO3s  H2O l


ii White precipitate dissolves


Calcium carbonate  water carbon IV oxide  Calcium hydrogen carbonate


CaCO3s  H2O l  CO2 g  CaHCO3 aq


5 State the chemical test for the presence of carbon IV oxide gas based on 4a and b above


Carbon IV oxide forms a white precipitate with lime water that dissolves in excess of the gas


6 State the composition of carbon IV oxide gas by volume in the air


About 003 by volume


BOXYGEN


a Occurrence


1 Fifty 50 of the earths crust consist of Oxygen combined with other elements eg oxides of metals


2 About 70 of the earth is water made up of Hydrogen and Oxygen


3 About 20 by volume of the atmospheric gases is Oxygen that form the active part of air


b School laboratory preparation


Oxygen was first prepared in 1772 by Karl Scheele and later in 1774 by Joseph Priestly It was Antony Lavoisier who gave it the name Oxygen


Procedure


Method 1 Using Hydrogen peroxide


Half fill a troughbasin with tap water Place a bee hive shelfstand into the water


Completely fill the gas jar with water and invert in onto the bee hive shelfstand


Clamp a round bottomed flask and set up the apparatus as below


Collect several gas jars of Oxygen covering each sample


Sample observation questions


1 What is observed when the hydrogen peroxide is added into the flask


Rapid effervescencebubblingfizzing


2 Describe the colour and smell of the gas


Colourless and odorless


3 aName the method of gas collection used


Over water


Upward delivery


Down ward displacement of water


bWhat property of Oxygen makes it to be collected using the method above


Slightly soluble in water


4 What is the purpose of manganese IV oxide


Manganese IV oxide is catalyst


A catalyst is a substance that speeds up the rate of a chemical reaction but remain chemically unchanged at the end of the reaction


Hydrogen peroxide decomposes slowly to form water and Oxygen gas


A little Manganese IV oxide speeds up the rate of decomposition by reducing the time taken for a given volume of Oxygen to be produced


5 Write the equation for the reaction


Hydrogen peroxide  Water  Oxygen


2H2O2 aq  2H2O l  O2 g


6 Lower a glowing splint slowly into a gas jar containing Oxygen gas State what is observed


The glowing splint relightsrekindles


Oxygen relightsrekindles a glowing splint This is the confirmatory test for the presence of Oxygen gas


Method 1 Using Sodium peroxide


Half fill a troughbasin with tap water Add four drops of phenolphthalein indicator


Place a bee hive shelfstand into the water


Completely fill a gas jar with water and invert in onto the bee hive shelfstand


Sample observation questions


1 What is observed when water is added


i Into the flask containing sodium peroxide


Rapid effervescencebubblingfizzing


ii Phenolphththalein


Remains colourless Phenolphthalein indicator is colourless in neutral solution


Colourless and odorless


3aName the method of gas collection used


Over water Oxygen is slightly soluble in water


4 Test the gas by lowering a glowing splint slowly into a gas jar containing the prepared sample


The glowing splint relightsrekindles This confirms the presence of Oxygen gas


5 Write the equation for the reaction


Sodium peroxide  Water  Sodium hydroxide  Oxygen


2Na2O2 aq  2H2O l  4NaOH aq  O2 g


1 Test the gas by lowering a glowing splint slowly into a gas jar containing the prepared sample


The glowing splint relightsrekindles


This confirms the presence of Oxygen gas


2 Write the equation for the reaction


Potassium Chlorate V  Potassium Chloride  Oxygen


2KClO3 aq  2KCl aq  3O2 g


3 What is the purpose of manganese IV oxide


Manganese IV oxide is catalyst


A catalyst is a substance that speeds up the rate of a chemical reaction but remain chemically unchanged at the end of the reaction


Potassium Chlorate V decomposes slowly to form potassium chloride and Oxygen gas


A little Manganese IV oxide speeds up the rate of decomposition by reducing the time taken for a given volume of Oxygen to be produced


cUses of Oxygen


1 Oxygen is put in cylinders for use where natural supply is not sufficiently enough This is mainly in


iMountain climbingMountaineeringat high altitudes the concentration of airoxygen is low Mountain climbers must therefore carry their own supply of oxygen for breathing


ii Deep sea divingDeep sea divers carry their own supply of Oxygen


iii Saving life in hospitals for patients with breathing problems and during anesthesia


2 A mixture of oxygen and some other gases produces a flame that is very hot


i Oxyacetyleneethyne flame is produced when Ethyneacetylene gas is burnt in pure oxygen The flame has a temperature of about 3000oCIt is used for welding cutting metals


iiOxyhydrogen flame is produced when Hydrogen is burn in pure oxygen The flame has a temperature of about 2000oCIt is used also for welding cutting metals


3 Oxyhydrogen mixture is used as rocket fuel


4 A mixture of charcoal petrol and liquid Oxygen is an explosive


d Chemical properties of Oxygen combustion


Oxygen is a very reactive non metal Many elements react with oxygen through burning to form a group of compounds called Oxides


Burningcombustion is the reaction of Oxygen with an elementsubstances


Reaction in which a substance is added oxygen is called Oxidation reaction Burningcombustion are an example of an oxidation reaction


Most non metals burn in Oxygenair to form an Oxide which in solution  dissolved in water is acidic in nature They turn blue litmus redeg Carbon IV oxideCO2 Nitrogen IV oxide NO2 Sulphur IV oxide SO2


Some non metals burn in Oxygenair to form an Oxide which in solution  dissolved in water is neutral in nature They dont turn blue or red litmus Eg Carbon II oxideCO Water H2O


All metals burns in Oxygenair to form an Oxide which in solutiondissolved in water is basicalkaline in nature They turn red litmus blueeg


Magnesium oxideMgO Sodium Oxide Na2O Copper II oxideCuO Elementssubstances burn faster in pure Oxygen than in air


Air contains the inactive part of air that slows the rate of burning of substanceselements


iReaction of metals with Oxygenair


The following experiments show the reaction of metals with Oxygen and air


I Burning Magnesium


Procedure


aCut a 2cm length piece of magnesium ribbon Using a pair of tongs introduce it to a Bunsen flame Remove it when it catches fire Observe


Place the products in a beaker containing about 5cm3 of water Test the solutionmixture using litmus papers


bCut another 2cm length piece of magnesium ribbon Using a pair of tongs introduce it to a Bunsen flame When it catches fire lower it slowly into a gas jar containing Oxygen


Place about 5cm3 of water into the gas jar Test the solutionmixture using litmus papers Test the solutionmixture using litmus papers


Observations


aIn air


Magnesium burns with a bright blindening flame in air forming white solidash powder Effervescencebubbles fizzing Pungent smell of urine Blue litmus paper remains blue Red litmus paper turns blue


b In pure Oxygen


Magnesium burns faster with a very bright blindening flame pure oxygen forming white solidash powder No effervescencebubbles fizzing No pungent smell of urine Blue litmus paper remains blue Red litmus paper turns blue


Explanation


Magnesium burns in air producing enough heat energy to react with both Oxygen and Nitrogen to form Magnesium Oxide and Magnesium nitride Both Magnesium Oxide and Magnesium nitride are white solidash powder


Chemical equations


Magnesium  Oxygen  Magnesium Oxide


2Mgs  O2g  2MgOs


Magnesium  Nitrogen  Magnesium Nitride


3Mgs  N2g  Mg3N2 s


Magnesium Oxide dissolves in water to form a basicalkaline solution of Magnesium hydroxide


Magnesium Oxide  Water  Magnesium hydroxide


2Mgs  O2 l  2MgOs


Magnesium Nitride dissolves in water to form a basicalkaline solution of Magnesium hydroxide and producing Ammonia gas Ammonia is also an alkalinebasic gas that has a pungent smell of urine


Magnesium Nitride  Water  Magnesium hydroxide  Ammonia gas


Mg3N2 s  6H2O l  3Mg OH2 aq  2NH3g


II Burning Sodium


Procedure


aCarefully cut a very small piece of sodium Using a deflagrating spoon introduce it to a Bunsen flame Remove it when it catches fire Observe


Place the products in a beaker containing about 20cm3 of water Test the solutionmixture using litmus papers


b Carefully cut another very small piece of sodium Using a deflagrating spoon introduce it to a Bunsen flame When it catches fire lower it slowly into a gas jar containing Oxygen


Place about 20 cm3 of water into the gas jar Test the solutionmixture using litmus papers Test the solutionmixture using litmus papers


Observations


aIn air


Sodium burns with a yellow flame in air forming a black solid Blue litmus paper remains blue Red litmus paper turns blue


b In pure Oxygen


Sodium burns faster with a golden yellow flame in pure oxygen forming a yellow solid Effervescencebubbles fizzing Gas produced relights glowing splint Blue litmus paper remains blue Red litmus paper turns blue


Explanation


aSodium burns in air forming black Sodium Oxide


Chemical equations


Sodium  Oxygenair  Sodium Oxide


4Nas  O2 g  2Na2Os


Sodium Oxide dissolves in water to form a basicalkaline solution of Sodium hydroxide


Sodium Oxide  Water  Sodium hydroxide


Na2Os  H2O l  2NaOH aq


bSodium burns in pure oxygen forming yellow Sodium peroxide


Sodium  Oxygen  Sodium peroxide


2Nas  O2 g  Na2O2 s


Sodium peroxide dissolves in water to form a basicalkaline solution of Sodium hydroxide Oxygen is produced


Sodium Oxide  Water  Sodium hydroxide  Oxygen


2Na2O2 s  2H2O l  4NaOH aq  O2 l


III Burning Calcium


Procedure


aUsing a pair of tongs hold the piece of calcium on a bunsen flame


Observe


Place the products in a beaker containing about 2cm3 of water Test the solutionmixture using litmus papers


bUsing a pair of tongs hold another piece of calcium on a Bunsen flame Quickly lower it into a gas jar containing Oxygen gas Observe


Place about 2cm3 of water Swirl


Test the solutionmixture using litmus papers


Observations


aIn air


Calcium burns with difficulty producing a faint red flame in air forming a white solid Blue litmus paper remains blue Red litmus paper turns blue


b In pure Oxygen


Calcium burns with difficulty producing a less faint red flame Oxygen forming a white solid Blue litmus paper remains blue Red litmus paper turns blue


Explanation


aCalcium burns in air forming white calcium Oxide Calcium Oxide coatcover the calcium preventing further burning


Chemical equations


Calcium  Oxygenair  calcium Oxide


2Cas  O2g  2CaOs


Small amount of Calcium Oxide dissolves in water to form a basicalkaline solution of Calcium hydroxide The common name of Calcium hydroxide is lime water


Calcium Oxide  Water  Calcium hydroxide


CaOs  H2O l  Ca OH 2 aq


IV Burning Iron


Procedure


aUsing a pair of tongs hold the piece of Iron woolsteel wire on a Bunsen flame


Observe


bUsing a pair of tongs hold another piece of Iron woolsteel wire on a Bunsen flame


Quickly lower it into a gas jar containing Oxygen gas Observe


Place about 2cm3 of water Swirl Test the solutionmixture using litmus papers


Observations


aIn air


Iron woolsteel wire burns producing an Orange flame in air forming a brown solid Blue litmus paper remains blue Red litmus paper turns faint blue


b In pure Oxygen


Iron woolsteel wire burns producing a golden Orange flame in Oxygen forming a Brown solid Blue litmus paper remains blue Red litmus paper turns faint blue


Explanation


aIron burns in air forming brown Iron III Oxide


Chemical equations


Iron  Oxygenair  Iron III Oxide


4Fes  3O2 g  2Fe2O3s


Very small amount of Iron III Oxide dissolves in water to form a weakly basicalkaline brown solution of Iron III hydroxide


Calcium Oxide  Water  Iron III hydroxide


Fe2O3s  3H2O l  2Fe OH 3 s


V Burning Copper


Procedure


aUsing a pair of tongs hold the piece of copper turningsshavings on a Bunsen flame


Observe


Place the products in a beaker containing about 2cm3 of water Test the solutionmixture using litmus papers


bUsing a pair of tongs hold another piece of Copper turningsshavings on a Bunsen flame Quickly lower it into a gas jar containing Oxygen gas Observe


Observations


aIn air


Copper turningsshavings burns with difficulty producing a green flame in air forming a black solid Blue litmus paper remains blue Red litmus paper turns faint blue


b In pure Oxygen


Copper turningsshavings burns less difficulty producing a green flame in Oxygen forming a Brown solid Blue litmus paper remains blue Red litmus paper turns faint blue


Explanation


aCopper burns in air forming black Copper II Oxide


Chemical equations


Copper  Oxygenair  Copper II Oxide


2 Cus  O2 g  2CuOs


Very small amount of Copper II Oxide dissolves in water to form a weakly basicalkaline blue solution of Copper II hydroxide


Copper II Oxide  Water  Copper II hydroxide


CuOs  H2O l  Cu OH 2 s


iReaction of non metals with Oxygenair


The following experiments show the reaction of non metals with Oxygen and air


I Burning Carbon


Procedure


aUsing a pair of tongs hold a dry piece of charcoal on a Bunsen flame


Observe


bUsing a pair of tongs hold another piece of dry charcoal on a Bunsen flame Quickly lower it into a gas jar containing Oxygen gas Observe


Place about 2cm3 of water Swirl Test the solutionmixture using litmus papers


Observations


Carbon chars then burns with a blue flame


Colourless and odorless gas produced


Solution formed turn blue litmus paper faint red


Red litmus paper remains red


Explanation


Carbon burns in air and faster in Oxygen with a blue nonsootynonsmoky flame forming Carbon IV oxide gas


Carbon burns in limited supply of air with a blue nonsootynonsmoky flame forming Carbon IV oxide gas


Carbon IV oxide gas dissolves in water to form weak acidic solution of Carbonic IV acid


Chemical Equation


Carbon  Oxygen  Carbon IV oxide


excess airoxygen


Cs  O2 g  CO2 g in excess air


Carbon  Oxygen  Carbon II oxide


limited airoxygen


2Cs  O2 g  2CO g in limited air


Carbon IV oxide  Water  Carbonic IV acid


CO2 g  H2O l  H2CO3 aq very weak acid


II Burning Sulphur


Procedure


aUsing a deflagrating spoon place sulphur powder on a Bunsen flame


Observe


Place the products in a beaker containing about 3cm3 of water Test the solutionmixture using litmus papers


b Using a deflagrating spoon place sulphur powder on a Bunsen flame Slowly lower it into a gas jar containing Oxygen gas Observe


Place about 5cm3 of water Swirl Test the solutionmixture using litmus papers


Observations


Sulphur burns with a blue flame


Gas produced that has pungent choking smell


Red litmus paper remains red


Explanation


Sulphur burns in air and faster in Oxygen with a blue nonsootynonsmoky flame forming Sulphur IV oxide gas


Sulphur IV oxide gas dissolves in water to form weak acidic solution of Sulphuric IV acid


Chemical Equation


Sulphur  Oxygen  Sulphur IV oxide


Ss  O2 g  SO2 g in excess air


Sulphur IV oxide  Water  Sulphuric IV acid


SO2 g  H2O l  H2SO3 aq very weak acid


III Burning Phosphorus


Procedure


aRemove a small piece of phosphorus from water and using a deflagrating spoon with a lid cover places it on a Bunsen flame


Observe


Carefully put the burning phosphorus to cover gas jar containing about 3cm3 of water Test the solutionmixture using litmus papers


b Remove another small piece of phosphorus from water and using a deflagrating spoon with a lid cover place it on a Bunsen flame


Slowly lower it into a gas jar containing Oxygen gas with about 5 cm3 of water Observe


Swirl Test the solutionmixture using litmus papers


Observations


Phosphorus catches fire before heating on Bunsen flame


Dense white fumes of a gas produced that has pungent choking poisonous smell


Solution formed turn blue litmus paper faint red


Red litmus paper remains red


Explanation


Phosphorus is stored in water On exposure to air it instantaneously fumes then catch fire to burn in air and faster in Oxygen with a yellow flame producing dense white acidic fumes of Phosphorus V oxide gas


Phosphoric V oxide gas dissolves in water to form weak acidic solution of Phosphoric V acid


Chemical Equation


Phosphorus  Oxygen  Phosphorous V oxide


4Ps  5O2 g  2P2O5s


Phosphorous V oxide  Water  Phosphoric V acid


P2O5s  3H2O l  2H3PO4 aq very weak acid


e Reactivity seriescompetition for combined Oxygen


The reactivity series is a list of elementsmetals according to their affinity for oxygen


Some metals have higher affinity for Oxygen than others


A metalelement with higher affinity for oxygen is placed higheron top of the one less affinity


The complete reactivity series of metalselements


Metals compete for combined Oxygen A metalelement with higher affinity for oxygen removes Oxygen from a metal lower in the reactivity seriesless affinity for Oxygen


When a metalelement gainsacquire Oxygen the process is called Oxidation


When metalelement donatelose Oxygen the process is called Reduction


An elementmetalcompound that undergoes Oxidation is called Reducing agent


An elementmetalcompound that undergoes Reduction is called Oxidizing agent


A reaction in which both Oxidation and Reduction take place is called a Redox reaction


Redox reaction between Magnesium and copper II Oxide


Procedure


Place about 2g of copper II oxide in a crucible with a lid Place another 2g of Magnesium powder into the crucible Mix thoroughly


Cover the crucible with lid Heat strongly for five minutes


Allow the mixture to cool Open the lid Observe


Observation


Colour change from black to brown White solid power formed


Explanation


Magnesium is higher in the reactivity series than Copper It has therefore higher affinity for Oxygen than copper


When a mixture of copper II oxide and Magnesium is heated Magnesium reduces copper II oxide to brown copper metal and itself oxidized to Magnesium oxide Magnesium is the reducing agent because it undergoes oxidation process


Copper II oxide is the oxidizing agent because it undergoes redox reduction process


The mixture should be cooled before opening the lid to prevent hot brown copper from being reoxidized back to black copper II oxide


The reaction of Magnesium and Copper II oxide is a reaction


Chemical equation


1 Copper II oxide  Magnesium  Magnesium oxide  Copper


black white ashsolid brown


CuOs  Mgs  MgOs  Cus


Oxidizing Agent Reducing Agent


2 Zinc II oxide  Magnesium  Magnesium oxide  Zinc


yellow when hot white ashsolid grey


ZnOs  Mgs  MgOs  Zns


Oxidizing agent Reducing agent


3 Zinc II oxide  Carbon  Carbon IV oxide gas  Zinc


yellow when hot colourless gas grey


ZnOs  Cs  CO2 g  Zns


The reactivity series is used during extraction of metals from their ore An ore is a rock containing mineral element which can be extracted for commercial purposes Most metallic ores occur naturally as


i oxides combined with Oxygen


ii sulphides combined with Sulphur


iii carbonates combined with carbon and Oxygen


Metallic ores that naturally occur as metallic sulphides are first roasted in air to form the corresponding oxide Sulphur IV oxide gas is produced eg


Copper I sulphide  Oxygen  Copper I Oxide  Sulphur IV oxide


Cu2Ss  O2 g  2Cus  SO2 g


Zinc II sulphide  Oxygen  Zinc II Oxide  Sulphur IV oxide


ZnSs  O2 g  Zns  SO2 g


Lead II sulphide  Oxygen  Lead II Oxide  Sulphur IV oxide


PbSs  O2 g  Pbs  SO2 g


Iron II sulphide  Oxygen  Iron II Oxide  Sulphur IV oxide


FeSs  O2 g  Fes  SO2 g


Metallic ores that naturally occur as metallic carbonates are first heated in air They decomposesplit to form the corresponding oxide and produce Carbon IV oxide gas eg


Copper II carbonate  Copper II oxide  Carbon IV oxide


CuCO3s  CuOs  CO2 g


Zinc II carbonate  Zinc II oxide  Carbon IV oxide


ZnCO3s  ZnOs  CO2 g


Lead II carbonate  Lead II oxide  Carbon IV oxide


PbCO3s  PbOs  CO2 g


Iron II carbonate  Iron II oxide  Carbon IV oxide


FeCO3s  FeOs  CO2 g


Metallic ores


WATER AND HYDROGEN


AWATER


Pure water is a colourless odorless tasteless neutral liquid Pure water does not exist in nature but naturally in varying degree of purity The main sources of water include rain springs borehole lakes seas and oceans


Water is generally used for the following purposes


i Drinking by animals and plants


ii Washing clothes


iii Bleaching and dyeing


iv Generating hydroelectric power


v Cooling industrial processes


Water dissolves many substancessolutes


It is therefore called universal solvent


It contains about 35 dissolved Oxygen which support aquatic fauna and flora


Water naturally exists in three phasesstates solid ice liquid water and gaseous water vapour


The three states of water are naturally interconvertible


The natural interconvertion of the three phasesstates of water forms the water cycle


Precipitation


Liquid water in land lakes seas and oceans use the solarsun energy to evaporatevapourize to form water vapourgas Solarsun energy is also used during transpiration by plants and respiration by animals


During evaporation the water vapour rises up the earths surface Temperatures decrease with height above the earth surface increase Water vapour therefore cools as it rises up At a height where it is cold enough to below 373Kelvin100oC Water vapour looses enough energy to form tiny droplets of liquid


The process by which a gaswater vapour changes to a liquid is called condensationliquidification


On further cooling the liquid looses more energy to form icesolid The process by which a liquidwater changes to a icesolid is called freezingsolidification Minutetiny icesolid particles float in the atmosphere and coalescejoin together to form clouds When the clouds become too heavy they fall to the earths surface as rainsnow as the temperature increase with the fall


Interconversion of the three phasesstates water


Evaporation Liquidification


boilingVapourization condensation


Melting Freezing liquidification


Solidification


Pure water has


i fixedconstantsharp freezing pointmelting point of 273K0oC


ii fixedconstantsharp boiling point of 373K100oC at sea level1 atmosphere pressure


iii fixed density of 1gcm3


This is the criteria of identifying purepurity of water


Whether a substance is water can be determined by using the following methods


a To test for presence of water using anhydrous copper II suphate VI


Procedure


Put about 2g of anhydrous copper II sulphate VI crystals into a clean test tube Add three drops of tap water Repeat the procedure using distilled water


Observation


Colour changes from white to blue


Explanation


Anhydrous copper II sulphate VI is white On adding water anhydrous copper II sulphate VI gainsreacts with water to form hydrated copper II sulphate VI


Hydrated copper II sulphate VI is blue Hydrated copper II sulphate VI contains water of crystallization


The change of white anhydrous copper II sulphate VI to blue hydrated copper II sulphate VI is a confirmatory test for the presence of water


Chemical equation


Anhydrous Hydrated copper II sulphate VI  Water  copper II sulphate VI


white blue


CuSO4s  5H2O l  CuSO45H2Os


b To test for presence of water using anhydrous cobalt II chloride


Put about 5cm3 of water into a clean test tube


Dip a dry anhydrous cobalt II chloride paper into the test tube


Repeat the procedure using distilled water


Colour changes from blue to pink


Anhydrous cobalt II chloride is blue On adding water anhydrous cobalt II chloride gainsreacts with water to form hydrated cobalt II chloride


Hydrated cobalt II chloride is pink


Hydrated cobalt II chloride contains water of crystallization


The change of blue anhydrous cobalt II chloride to pink hydrated cobalt II chloride is a confirmatory test for the presence of water Chemical equation


Anhydrous Hydrated cobalt II chloride  Water  cobalt II chloride


Blue pink


CoCl2 s  5H2O l  CoCl25H2Os


Burning a candle in air


Most organic substancesfuels burn in air to produce water Carbon IV oxide gas is also produced if the air is sufficientexcess


Procedure


Put about 2g of anhydrous copper II sulphate VI crystals in a boiling tube


Put about 5cm3 of lime water in a boiling tube


Light a small candle stick Place it below an inverted thistlefilter funnel


Collect the products of the burning candle by setting the apparatus as below


Set up of apparatus


Observation


The sanction pump pulls the products of burning into the inverted funnel Colour of anhydrous copper II sulphate VI changes from white to blue A white precipitate is formed in the lime watercalcium hydroxide


Explanation


When a candle burn it forms a water and carbon IV oxide


Water turns anhydrous copper II sulphate VI changes from white to blue


Carbon IV oxide gas forms white precipitate when bubbled in lime watercalcium hydroxide


Since


i hydrogen in the wax burn to form water


Hydrogen  Oxygen  Water


from candle from the air


2H2 g  O2 g  2H2O gl


ii carbon in the wax burn to form carbon IV oxide


Cs  O2g  CO2 g


The candle before burning therefore contained only Carbon and Hydrogen only A compound made up of hydrogen and carbon is called Hydrocarbon


A candle is a hydrocarbon


Other hydrocarbons include Petrol diesel Kerosene and Laboratory gas Hydrocarbons burn in air to form water and carbon IV oxide gas


Hydrocarbons  Oxygen  Water  Oxygen


Water pollution


Water pollution takes place when undesirable substances are added into the water Sources of water pollution include


iIndustrial chemicals being disposed into water bodies like rivers lakes and oceans


iiDischarging untreated raw sewage into water bodies


iiiLeaching of insecticidesherbicides form agricultural activities into water bodies


ivDischarging nonbiodegradable detergents after domestic and industrial use into water bodies


vPetroleum oil spilling by ships and oil refineries


viToxicpoisonous gases from industries dissolving in rain


vii Acidic gases from industries dissolving in rain to form acid rain


viiiDischarging hot water into water bodies This reduces the quantity of dissolved Oxygen in the water killing the aquatic fauna and flora


Water pollution can be reduced by


i Reducing the use of agricultural fertilizers and chemicals in agricultural activities


ii Use of biological control method instead of insecticides and herbicides


iii Using biodegradable detergents


REACTION OF WATER WITH METALS


Some metals react with water while others do not The reaction of metals with water depends on the reactivity series The higher the metal in the reactivity series the more reactive the metal with water The following experiments shows the reaction of metals with cold water and water vapoursteam


aReaction of sodium potassium with cold water


Procedure


Put about 500cm3 of water in a beaker Add three drops of phenolphthalein indicatorlitmus solutionuniversal indicator solutionmethyl orange indicator into the water


Cut a very small piece of sodium Using a pair of forceps put the metal into the water


Observation


Sodium melts to a silvery ball that floats and darts on the surface decreasing in size Effervescencefizzing bubbles of colourless gas produced


Colour of phenolphthalein turns pink


Colour of litmus solution turns blue


Colour of methyl orange solution turns Orange


Colour of universal indicator solution turns blue


Explanation


Sodium is less dense than water Sodium floats on water and vigorously reacts to form an alkaline solution of sodium hydroxide and producing hydrogen gas Sodium is thus stored in paraffin to prevent contact with water


Chemical equation


Sodium  Water  Sodium hydroxide  Hydrogen gas


2Nas  2H2O l  2NaOH aq  H2g


To collect hydrogen gas Sodium metal is forced to sink to the bottom of the troughbeaker by wrapping it in wire gauzemesh


Potassium is more reactive than Sodium On contact with water it explodesburst into flames An alkaline solution of potassium hydroxide is formed and hydrogen gas


Potassium  Water  Potassium hydroxide  Hydrogen gas


2Ks  2H2O l  2KOH aq  H2g


Caution Reaction of Potassium with water is very risky to try in a school laboratory


bReaction of Lithium Calcium with cold water


Procedure


Put about 200cm3 of water in a beaker Add three drops of phenolphthalein indicatorlitmus solutionuniversal indicator solutionmethyl orange indicator into the water


Cut a small piece of Lithium Using a pair of forceps put the metal into the water


Repeat with a piece Calcium metal


Observation


Lithium sinks to the bottom of the water Rapid effervescencefizzing bubbles of colourless gas produced


Colour of phenolphthalein turns pink


Colour of litmus solution turns blue


Explanation


Lithium and calcium are denser than water Both sink in water and vigorously react to form an alkaline solution of Lithium hydroxide  calcium hydroxide and producing hydrogen gas Lithium is more reactive than calcium It is also stored in paraffin like Sodium to prevent contact with water


Chemical equation


Lithium  Water  Lithium hydroxide  Hydrogen gas


2Lis  2H2O l  2LiOH aq  H2 g


Calcium  Water  Calcium hydroxide  Hydrogen gas


Cas  2H2O l  Ca OH 2aq  H2 g


c Reaction of MagnesiumZinc Iron with Steamwater vapour


Procedure method1


Place some wet sand or cottonglass wool soaked in water at the bottom of an ignitionhard glass boiling tube


Polish magnesium ribbon using sand paper


Coil it at the centre of the ignitionhard glass boiling tube


Set up the apparatus as below


Heat the wet sand or cottonglass wool soaked in water gently to


i Drive away air in the ignitionhard glass boiling tube


ii Generate steam


Heat the coiled ribbon strongly using another burner Repeat the experiment using Zinc powder and fresh Iron filings


Set up of apparatus


Observations


iWith Magnesium ribbon


The Magnesium glows with a bright flame and continues to burn even if heating is stopped


White solid ash formed


White solid ash formed dissolve in water to form a colourless solution


Colourless gas producedcollected that extinguish burning splint with pop sound


ii With Zinc powder


The Zinc powder turns red hot on strong heating


Yellow solid formed that turn white on cooling


White solid formed on cooling does not dissolve in water


iiiWith Iron fillings


The Iron fillings turn red hot on strong heating


Dark blue solid formed


Dark blue solid formed does not dissolve in water


Procedure method 2


Put some water in a round bottomed flask


Coil it at the centre of a hard glass tube


Set up the apparatus as below


Heat water strongly to boil so as to


i drive away air in the glass tube


ii generate steam


Observations


iWith Magnesium ribbon


White solid ash formed


ii With Zinc powder


Explanations


aHot magnesium burn vigorously in steam The reaction is highly exothermic generating enough heatenergy to proceed without further heating


White Magnesium oxide solidash is left as residue


Hydrogen gas is produced It extinguishes a burning splint with a pop sound


Chemical Equation


Magnesium  Steam  Magnesium oxide  Hydrogen


Mgs  H2Og  MgOs  H2g


Magnesium oxide reacts dissolves in water to form an alkaline solution of Magnesium oxide


Magnesium oxide  Water  Magnesium hydroxide


MgOs  H2Ol  MgOH 2 aq


bHot Zinc react vigorously in steam forming yellow Zinc oxide solidash as residue which cools to white


Zinc  Steam  Zinc oxide  Hydrogen


Zns  H2Og  ZnOs  H2g


Zinc oxide does not dissolve in water


cHot Iron reacts with steam forming dark blue tri iron tetra oxide solidash as residue


Iron  Steam  Tri iron tetra oxide  Hydrogen


2Fes  4H2Og  Fe2O4s  4H2g


Tri iron tetra oxide does not dissolve in water


dAluminum reacts with steam forming an insoluble coatcover of impervious layer of aluminum oxide on the surface preventing further reaction


e Lead Copper Mercury Silver Gold and Platinum do not react with either water or steam


HYDROGEN


Occurrence


Hydrogen does not occur free in nature It occurs as Water and in Petroleum


School laboratory Preparation


Procedure


Put Zinc granules in a roundflatconical flask Add dilute sulphuric VI Hydrochloric acid


Add about 3cm3 of copper II sulphate VI solution


Collect the gas produced over water as in the set up below


Discard the first gas jar Collect several gas jars


ObservationExplanation


Zinc reacts with dilute sulphuric VIhydrochloric acid to form a salt and produce hydrogen gas


When the acid comes into contact with the metal there is rapid effervescence bubbles fizzing are produced and a colourless gas is produced that is collected


i Over water because it is insoluble in water


ii Through downward displacement of airupward delivery because it is less dense than air


The first gas jar is impure It contains air that was present in the apparatus


Copper II sulphate VI solution act as catalyst


Chemical equation


a Zinc  Hydrochloric acid  Zinc chloride  Hydrogen


Zns  2HCl aq  ZnCl2 aq  H2 g


Ionic equation


Zn s  2H aq  Zn2 aq  H2 g


Zinc  Sulphuric VI acid  Zinc Sulphate VI  Hydrogen


Zns  H2SO4 aq  ZnSO4 aq  H2 g


b Chemical equation


Magnesium  Hydrochloric acid  Magnesium chloride  Hydrogen


Mgs  2HCl aq  MgCl2 aq  H2g


Mg s  2H aq  Mg2 aq  H2 g


Magnesium  Sulphuric VI acid  Magnesium SulphateVI  Hydrogen


Mgs  H2SO4 aq  MgSO4 aq  H2g


c Chemical equation


Iron  Hydrochloric acid  Iron II chloride  Hydrogen


Fes  2HCl aq  FeCl2 aq  H2 g


Fe s  2H aq  Fe2 aq  H2 g


Iron  Sulphuric VI acid  Iron II Sulphate VI  Hydrogen


Fes  H2SO4 aq  FeSO4 aq  H2 g


Note


1 Hydrogen cannot be prepared from reaction of


iNitric V acid and a metal Nitric V acid is a strong oxidizing agent It oxidizes hydrogen gas to water


ii Dilute sulphuric VI acid with calciumBariumLead because Calcium sulphate VI Barium sulphate VI and Lead II sulphate VI salts formed are insoluble Once formed they covercoat the unreacted calciumBariumLead stopping further reaction and producing very small amountvolume of hydrogen gas


iii Dilute acid with sodiumpotassium The reaction is explosive


Properties of Hydrogen gas


aPhysical properties


1 Hydrogen is a neutral colourless and odorless gas When mixed with air it has a characteristic pungent choking smell


2 It is insoluble in water thus can be collected over water


3 It is the lightest known gas It can be transferred by inverting one gas jar over another


bChemical properties


iBurning


I Hydrogen does not support burningcombustion When a burning splint is inserted into a gas jar containing Hydrogen the flame is extinguished put off


II Pure dry hydrogen burn with a blue quiet flame to form water When a stream of pure dry hydrogen is ignited it catches fire and continues to burn with a blue flame


III Impure air mixed with hydrogen burns with an explosion Small amount volume of air mixed with hydrogen in a test tube produce a small explosion as a pop sound This is the confirmatory test for the presence of Hydrogen gas A gas that burns with a pop sound is confirmed to be Hydrogen


iiRedox in terms of Hydrogen transfer


Redox can also be defined in terms of Hydrogen transfer


iOxidation is removal of Hydrogen


iiReduction is addition of Hydrogen


iiiRedox is simultaneous addition and removal of Hydrogen


Example


When a stream of dry hydrogen gas is passed through black copper II oxide hydrogen gas gains the oxygen from copper II oxide


Black copper II oxide is reduced to brown copper metal


Black copper II oxide thus the Oxidizing agent


Hydrogen gas is oxidized to Water Hydrogen is the Reducing agent


Set up of apparatus


aChemical equation


i In glass tube


Copper II Oxide  Hydrogen  Copper  Hydrogen gas


oxidizing agent reducing agent


black brown


CuO s  H2g  Cus  H2Ol


ii when excess Hydrogen is burning


Oxygen  Hydrogen  Water


O2 g  2H2 g  2H2O l


bChemical equation


Lead II Oxide  Hydrogen  Lead  Hydrogen gas


brown when hot grey


yellow when cool


PbO s  H2 g  Pbs  H2O l


O2 g  2H2 g  2H2Ol


cChemical equation


Iron III Oxide  Hydrogen  Iron  Hydrogen gas


Dark grey grey


Fe2O3 s  3H2 g  Fes  3H2O l


iii Water as an Oxide as Hydrogen