LABORATORY RULES- do not enter the science laboratory without the teacher’s permission .- No food or drinks are to be consumed in the laboratory.- Do not play/tamper with the equipment .- Keep your desk/working space clean .- Seek permission before carrying out an experiment .- Read all instructions carefully before any experiment- Prepare all apparatus and arrange them such that you will NOT knockthem over .- Wash all apparatus after the experiment and return them to their properplaces .- Dispose waste materials in proper waste bins .- Never throw solids or corrosive liquids in the sink .- Wash your hands thoroughly before leaving the science lab .- Do not remove chemicals and apparatus from the science laboratory .
What is science?Science is the study of the world around us throughobservation , experimentation and analysis .3 main areas of the study in science : Chemistry ,Physics and Biology .These different areas of science may link one anotherto form other branches of studies such asBIOCHEMISTRY , PHYSICAL CHEMISTRY ANDBIOPHYSICS.
Life long skills and attitudesBesides a keen sense of curiosity , a good scientist shouldalso have the spirit of inquiry .Thus compromises qualities such as keen observation ,open-mindedness , patience , objectivity , integrity ,creativity and perseverance , scientists should beaware of what’s happening around the world . Thisleads to questioning about what they see and makingsense of the data that they collect from theirobservations . They need to work well with their peers .The skills of science inquiry – systematic observation ,experimentation and analysis.
LABORATORY APPARATUSTEST TUBEFILTER FUNNELBEAKERCONICAL FLASKFLAT-BOTTOMEDFLASKRETORT STANDTRIPOD STANDEVAPORATING DISHMEASURINGCYLINDERLiquid holdingand filtrationBUNSEN BURNERSource of heat / toraise a flame abovethe table , highenough for heating.For supportingapparatusDURING heatingFor containing smallamounts ofchemicals forheating/ for mixingsolutions/liquidsFor transferring liquidinto containers with asmall opening ./ Forseparating solids fromliquids by the use of aFILTER PAPERFor containing andmixing chemicals andliquids to produce agas when heating isNOT requiredBELL JARTo separate theset-up of anexperiment fromthe surroundings.For mixing and heatingthe chemicals toproduces gas whenheating IS required .For supportingapparatus duringexperimentsTo evaporate theliquid IN a solutionover a BunsenburnerTo measurevolumes ofobjects
BUNSEN BURNERThe yellow colour in aluminous flame is basicallyfrom hot particles of soot inthe flame . In a blue flame ,there are no particles of SOOTto give that incandescentradiationThe difference between ayellow and blue flame dependon the amount of oxygen thatis mixed in with the fuel .More oxygen means that thecombustion reaction is moreefficient and more energy isreleased . Remember that themore blue the visible lightappears , the more energythat light will have
BUNSEN BURNERThe non-luminous flame exists when there is acomplete combustion or complete burningprocess . It happens when there is more thanthe enough oxygen in the surroundings or in theplace where the process will happen.The temperature of a non-luminous flame ishotter than the temperature of a luminousflame.
The scientific methodThe scientific method consists of main steps a person could take to solve a problem orfind out new things.Step 1Make observationsStep 2Analyse ,infer, predict and hypothesiseStep 3PLAN experiments to test your hypothesis- record - analyse - concludeStep 4Record and analyse your resultsStep 5DISCUSS with othersStep 6Summarise your results and draw conclusionsStep 7Communicate your findings to others
What is technology ?Technology is the application of scientific knowledge forpractical purposes .BENEFITS OF TECHNOLOGY Invention of medicines .Invention of the telephone ,computer, radio and televisionfor communication and dissemination of information .ABUSES OF TECHNOLOGY Sometimes technology can cause harm to the environmentand society , especially when misused.what do you mean by ‘when misused’?- should you blame the soldiers or the weapons for the liveslost during battles ?- should you blame the car or the driver for road accidents?
Can technology solve ALL ourproblems ?No , although technology has helped us in manyways, it cannot possibly solve all our problems suchas natural disasters but however , we can usetechnology to predict the occurrence of naturaldisasters though they are not always accurate.
WHERE DO SCIENTISTS WORK?- Laboratories- Rainforests- SpaceScience is not confined to the laboratory buteverywhere else too.Doing field work is going outdoors , away from thelaboratory to collect data .
Hazard symbolsExplosive ToxicFlammable CorrosiveIrritable BiohazardousRadioactiveSubstance willreact violentlywhen heated orstruckSubstancecatches fireeasilySubstance producesvapours or fumes whichirritates the eyes, nose andthroatSubstance emitsradiationSubstance isharmful insmall dosesSubstance willeat away othersubstancesPoisonous substanceof a biologicalnature
VariablesIn the process of testing a hypothesis , the things thathave an effect on the experiment are calledvariables , THE INDEPENDENT VARIABLE is thevariable you CHANGE.The variables you DO NOT CHANGE are calledCONTROLLED VARIABLES / THE CONTROL.The variable that we measure , which DEPENDS onthe independent variable is called the DEPENDENTVARIABLE .
TIME, RATE AND SPEEDTIME is the DURATION OF AN EVENT.S.I. unit (international system of units) oftime is the SECOND and represented by thesymbol ‘s’ .Other units of time : MINUTE (min) , HOUR(h) and millisecond (ms) .Time can also be expressed in terms of days, weeks , months and years.INSTRUMENTS TO MEASURETIMETo measure a short period of timeACCURATELY , we use a STOPWATCHTHERE ARE TO TYPES : mechanical andelectronicMECHANICAL STOPWATCH- The mechanical stopwatch hasa minute scale and a secondscale- The smallest division on themechanical stopwatch is 0.1 s .Thus the mechanical stopwatchis accurate to 0.1 s .ELECTRONICSTOPWATCH- The electronic stopwatch/thedigital stopwatch is MOREaccurate than the mechanicalstopwatch .- It can measure time intervalsaccurate to 0.01 s ( 2 sig . Fig)- It can also record timeintervals in hours , unlike themechanical stopwatch
CONVERSION OF UNITSLENGTHS IN OTHER UNITS what to do? LENGTH IN METERS30 dm divide 10 = 37km times 1000= 70002500cm divide 100= 2532km times 100= 3200600mm divide 1000= 0.674.5 cm divide 100= 0.745
S.I UNITSPrefix Value SymbolGiga One billion GMega One million MKilo One thousand kDeci One tenth dCenti One hundredth CMilli One thousandth mMicro One millionth uNano One billionth nPhysical quantity Value SymbolLength Metre mWeight Mass Kilogram kgTemperature Degree celcius Kelvin KTime Second s
RATE IS AN EXPRESSION OF HOW ONE QUANTITYCHANGES WITH TIME .RATES ARE USEFUL FOR MAKING FAIR COMPRISONSPHONE CHARGES , INTERNET ACCESS PLANS , BANKLOAN INTEREST RATES AND INFLATION RATES ARESOME EXAMPLES OF RATES IN REAL LIFE
UNIT AND MEASUREMENTSMEASURING TAPE & METRE RULEMEASURING TAPE / METRE RULE = measuringshort lengths .METRE RULE = measure to 100 cm (1m)MEASURING TAPE = FLEXIBLE , SEVERAL METRES ,ACCURATE TO 0.1 CM.
VERNIER CALIPERSVernier caliper = used to measure Internal andexternal diameters of cylinder or spherical objects.= have tails that are used tomeasure depth of narrow tubes= accurate to 0.01 cm
VERNIER CALIPERSPARALLAX ERROR =Parallax error arises when theposition of the eye is not at the same level as themarkings to be read .ZERO ERROR =Zero error in a vernier caliperarises when the zero marking on the main scaledoes not coincide with the zero marking on thescale , with the jaws if the vernier caliper closed.
VERNIER CALIPERSUsing the Vernier calipers1) Close the jaws of the Vernier calipers . Ensure thatthe zero marking on the Vernier scale is in line withthe zero marking on the main scale2) Place the object within the jaws of the Verniercalipers and clamp it firmly in place .3) Read the length
CHOOSING THE RIGHT INSTRUMENTSLength to be measured Instruments to be used Accuracy of instrumentBetween 0 and 10 cm Vernier calipers To the nearest 0.01 cm10 cm to 100cm (1m) Meter rule To the nearest mm5cm and above Measuring tape /contractor’s ruleTo the nearest mm ( shortlengths )To the nearest cm ( VERYlong lengths )
SQUARE GRIDSquare grid – finding area4km4kmCount the onesmore than half orhalf only, as 1 .123 455 x 16= 80(Not the mostaccurate way.)
FORMULAS FOR MEASURING AREAAND VOLUMESQUARE = Length x LengthRECTANGLE = Length x BreadthTRIANGLE = ½ x Base x HeightCIRCLE = r (square)CUBE = Length x Length x LengthCUBOID = Length x Breadth x HeightPRISM = Base area x Height= 1/2 x Length x Breadth x HeightPARALLELOGRAM = Base x HeightCONE = 1/3 x x radius2 x heightSPHERE= 4/3 X x radius3
FORMULAS FOR MEASURINGVOLUMEPYRAMID = Base area x Height= 1/3 x Length x Length x HeightCYLINDER = Base area x Height= x r(square) x HeightSPHERE = 4/3 r (cube)CONE = 1/3 r(square)Height
MEASURING VOLUME OF LIQUIDVolume of liquid – measured in cm(cube) or litres (1 litreis 1000cmc(cube))Instruments = MEASURING CYLINDER , BURETTE, PIPETTER AND VOLUMETRIC FLASKCURVE SEEN AT THE SURFACE OF A LIQUID IS KNOWN ASA MENISCUS .=* To prevent parallax error , the eye must bepositioned at the same level as the meniscus
MEASURING MASS• MASS IS THE AMOUNT OF SUBSTANCE THATAN OBJECT HAS .• SI UNIT : KG• MEASURED USING – DOUBLE BEAM BALANCE- ELECTRONIC BALANCE
MEASURING VOLUME OF IRREGULARSOLIDSVOLUME OF IRREGULAR SOLIDS CAN BE FOUNDUSING THE DISPLACEMENT METHOD- Need a displacement canVOLUME OFTHE SOLID
ELEMENTSe.g); ELEMENTS : sucrose solution , ammonia , bromine and protein;METALS: bronze , copper , mercury- Oxygen makes up 21% of the atmosphere air .- An element is a pure chemical substance consisting of one type of atom.- Magnesium , iron and zinc are grey solids at room temperature .- Nitrogen makes up 78% of the atmosphere air .- Copper is a reddish-brown solid.- Water is made up of the elements hydrogen and oxygen.- Mercury is a silver-coloured liquid metal that expands evenly on heating.- Iodine is used as an antiseptic in medicines to prevent infections from wounds (usually purple in colour then to brownish-yellow).- Metals are usually present in the form of solids at room temperature.- Hydrogen reacts violently with air and it is said to be explosive .- Non-metals are usually dull in apprearance .
CLASSIFYING METALS AND NON-METALS-Elements can be classified as metals and non-metals . (depending on theirproperty)-Except for mercury , all metallic elements are solids at room temperature .-Non-metallic elements exist in solid , liquid and gas .METALS NON-METALSShiny surface Dull surfaceDuctile Non-ductileMalleable BrittleHigh melting point Low melting pointHigh density Low densityGood electrical conductor Poor electrical conductorGood thermal conductor Poor thermal conductorProperties
CLASSIFYING ELEMENTS BY STATEDifferent elements exist in difference states atroom temperatureIn the periodic table , there are 11 elements thatare in gaseous state , 2 in liquid state and therest in solid state
PERIODIC TABLEVertical groups ( SIMILAR chemical properties)Horizontal periodsMetalloids properties are metal + non-metal. They are solidsthat can be shiny or dull.They conduct heat and electricity better than non-metals but notas well as metals.They are ductile and malleable.Metal alloy Mixture of 2 or more metals .
GROUPS AND PERIODSGroups• Columns of elements arecalled groups or families.• Elements in each group havesimilar but not identicalproperties.• For example, lithium (Li),sodium (Na), potassium (K),and other members of groupIA are all soft, white, shinymetals.• All elements in a group havethe same number of valenceelectrons.Periods• Each horizontal row ofelements is called a period.• The elements in a periodare not alike in properties.• In fact, the propertieschange greatly across evengiven row.• The first element in a periodis always an extremelyactive solid. The lastelement in a period, isalways an inactive gas.
FLOATING AND SINKINGWhen an object floats on a liquid , the object is lessdense than the liquid .When an object sinks in a liquid , the object isdenser than the liquid .The density of water is 1 g/cm(cube) . An objectwith a density LOWER than 1 g/cm(cube) will FLOATon water . An object with a density HIGHER than 1g/cm(cube) will sink in water
ELEMENTS,COMPOUNDS,MIIXTURESElectrolysis – break down of substances usingelectricityNitrogen 78%Oxygen 21%Carbon dioxide 0.03%Water Vapour 1%IN THE EARTH’S CRUST THE 2 MOST ABUNDANT ELEMENTS AREOXYGEN(47%) AND SILICON (28%)Poor conductor insulator
PHYSICAL PROPERTIESStrength- is the ability to support a heavy load without breaking or tearingTransparency – ability of a material to allow light to pass through.Ductility-is the ability of a material to be drawn into wires without breakingHardness –is the ability to withstand scratching by another materialElectrical conductivity-is the ability to allow electricity pass throughThermal conductivity-is the ability to allow heat to pass throughMalleability-is the ability of a material to be moulded into shapesFlexibility –is the ability to bend or stretch without breakingMelting point –is the temperature at which a solid changes into liquidBoiling point-is the temperature in which liquid changes into gasDensity – refers to mass per unit volume (mass/volume)-mass over volume
PROPERTIES OF METAL ELEMENTSCOPPER- Reddish Brown- Good conductor of electricity- Ductile-Corrosion resistant-StrongZINC-Grey solid-Prevents rusting of iron-Good conductor of electricity-Strong-Corrosion resistantALUMINIUM-Silvery shiny solid-Low density-strong and light-malleable-corrosion resistantMERCURY-Silvery liquid-does not react easily withother chemicals-Mercury vapour isfluorescent-Good conductor of heat- Expands evenly ofheatingMAGNESIUM-Grey solid-Burns with dazzlinglight-forms alkali toneutralise excessacid in stomachIRON-Grey solid-Good conductor of heatand electricity-Ductile-strong-Magnetic
PROPERTIES OF NON-METALELEMENTSIODINE-Black crystals-poisonous-antiseptic-prevents woundinfectionCHLORINE-greenish-yellowgas-bleaches dyes-poisonousSULPHUR-yellow powdery solid-poisonous-soluble in organicsolvent (alcohol) but notin waterDIAMOND(CARBON)-hardest substanceknown to man-can be polished toshiny , reflecting ,transparent solidHYDROGEN-colourless gas-gas with lowestdensity-explosiveCARBON (GRAPHITE)-black solid-smooth-lightweight-good conductor ofelectricity
PROPERTIES OF NON-METALELEMENTSOXYGEN-colourless gas- Essential for life- Does not burn butsupports combustion(allows other things toburn)NITROGEN-colourless gas-unreactive , does not burnor support combustion-low boiling point
WHAT ARE COMPOUNDS?When different elements are chemically combinedtogether , they form new substances known ascompounds.e.g: Hydrogen + Oxygen = water (compound )Sodium + Chloride = table salt (compound)Carbon + Hydrogen + Oxygen = sugar (compound)Calcium + Carbon + Oxygen = chalk (compound)
CHARACTERISTICS OF COMPUNDSTo form water the ratio of hydrogen and oxygen thatcombine chemically is always 1:8 .HOW ARE COMPOUNDS FORMED?Made of elements , other compounds , both elementsand compounds – FORMED BY CHEMICAL REACTION- 2 main methods of forming compounds: COMBINATION: DECOMPOSITION (heated to break down )Combustion
COMBINATIONOne common example of combination iscombustion .THIS HAPPENS WHEN ELEMENTS ORCOMPOUNDS BURN AND COMBINE WITHOXYGEN TO FORM ONE OR MORE NEWCOMPOUNDS .Eg.) carbon + oxygen = carbon dioxide
DECOMPOSITIONDecomposition occurs when 2 or more complexcompounds are heated to break them down intosimpler compounds.It decomposes to form water vapour and carbon.E.G ) sugar (compound) Water vapour (compound) + Carbon ( element )
BREAKING DOWNSome compounds can be broken down intosimpler substances when EXPOSED TO LIGHT .For example CFC ( CHLOROFLUOROCARBON )compound is Styrofoam is broken down bysunlight into a hazardous substance . THISSUBSTANCE DEPLETES THE OZONE LAYER .
MIXTURESProperties of Mixtures :When a mixture is formed , no chemical reactionoccurs .A MIXTURE HAS THE PROPERTIES OF ITSCONSTITUENT SUBSTANCES .A mixture can be separated easily by physicalmethods (i.e. without involving chemical reaction).The components in mixtures are not mixed in anyfixed proportion.Water bath is to ensure gentle and even heating .
DIFFERENT KINDS OF MIXTURESSolid-solid ( Alloys )Liquid-Liquid ( Vinegar)Solid-Liquid ( Lotion )Liquid-Gas ( Foam )Gas-gas ( air )
MAGNETIC ATTRACTIONUsed to separate magnetic materials from non-magnetic materials .Separating iron fromsulphurUSES OF MAGNETIC ATTRACTION- Food processing- To salvage scrap iron and steel
FILTRATIONBAKERS MUST USE A SIEVE TOREMOVE LUMPS FROM THEFLOUR MIXTURE.Filtration works by allowingsmall liquid particles through ,but not large solid particles.The filter paper has tiny pores thatallow the liquid component to passthrough it . The insoluble liquid solidparticles that are too large to passthrough it . The insoluble liquid iscalled the residue and the liquid thatpasses through the filter paper is called
EVAPORATIONEvaporation(to dryness ) is used to separate adissolved solid from a liquid . The dissolved solidmust be stable to hear and NOT decomposes .When the mixture has completely evaporated ,no water is left behind . The solid salt left behindas the RESIDUE.
DISTILLATIONDistillation is used to separate a pure liquid froma solid-liquid or a liquid-liquid mixture . Thepure liquid collected from distillation is calledthe distillate .condensationVaporizationEnsure heating is gentle (water bath)
DESALINATION PLANTSDesalination is a treatment process thatremoves dissolved salts from sea water toobtain pure water . Distillation is one of thetraditional methods used to carry outdesalination .
FRACTINAL DISTILLATIONGas –high temperature &HIGH KINETICENERGY .Fractional distillation also dependson the difference in the boilingpoints of different liquids .Crude oil is a mixture of liquids with differentboiling points . Oil refineries use fractionaldistillation to separate crude oil into usefulproducts such as petrol , diesel , keroseneSEPARATE CREAM AND MILK AS MILK ISSOULUBLE IN CREAM.
PAPER CHROMATOGRAPHYSeparation methods like filtration and distillation require alarge amount of the mixture to be separated .This is usually used to separate mixtures of colouredsubstances such as ink and dyes.Paper chromatography makes use of the fact that differentpaces . Similarly , different substance move through particularmediums at different rates.Paper chromatography makes use of the fact that differentsubstances dissolve to different extents in a mixture .
REVERSE OSMOSISIn reverse osmosis , sea water is pre-treated to remove debrisand contaminants such as oil , grease and suspended solids . Thepre-treated sea water is then pumped at high pressure throughpartially-permeable membrane to remove all traces if bacteria ,viruses , chemicals and dissolve minerals .WATERMOLECULES
What is reverse osmosis?Reverse osmosis (RO) is a membrane-technology filtration method that removes manytypes of large molecules and ions fromsolutions by applying pressure to the solutionwhen it is on one side of a selective membrane.The result is that the solute is retained on thepressurized side of the membrane and the puresolvent is allowed to pass to the other side. Tobe "selective," this membrane should not allowlarge molecules or ions through the pores(holes), but should allow smaller components ofthe solution (such as the solvent) to pass freely.
NEWaterTOWARDS A SUSTAINABLE WATER SUPPLY• NEWater currently meets 30% of Singapore’s totalwater demand.• NEWater is high-grade reclaimed water producedfrom treated used water that is purified furtherusing advanced membrane technologies, makingthe water ultra-clean and safe to drink.• The second stage of the NEWater productionprocess is known as Reverse Osmosis (RO). InRO, a semi-permeable membrane is used.• Consequently, undesirable contaminants such asbacteria, viruses, heavy metals etc., cannot passthrough the membrane.• Hence, NEWater is RO water and is free fromviruses, bacteria and contains negligible amount ofsalts and organic matters.
GENERAL QUESTIONDESCRIBE and EXPLAIN how you would separate amixture of sugar and chalk . (4 marks)Add water to the mixture (1/2 mark) and stirwell to mix (1/2 mark) . This dissolves the sugar(1/2 marks) to form a sugar solution (1/2 marks). Carry out filtration(1 mark) . Separate sugarsolution and chalk . The residue is the chalkand the filtrate is the sugar solution (1 mark).
SOLUTIONS AND SUSPENSIONSWhat are solutions ?Solutions are mixtures in which soluble particles are completelydissolved in a liquid or gas.HOMOGENEOUS : same throughoutBUBBLES : pocket of airWhat are suspensions?Suspensions are mixtures in which insoluble particles are suspended ina liquid or gas .What is solubility ?Solubility is the maximum amount of solute that can dissolve in100grams of solvent at a given temperature .
SOLUTE , SOLVENT AND SOLUTIONThe solute is the substance that dissolves in asolvent .The solvent is the substance that dissolves in thesolute .The solution is the mixture of the solute andsolvent .
CHARACTERISTICS OF A SOLUTIONHomogeneousWhen left on it’s own , the solute does notseparate from the solvent .When filtered , no residual particles will remainon the filter paper . It will pass throughcompletely .
SUSPENSIONIt is the exact opposite of a solution .A SUSPENSION IS A MIXTURE IN WHICHINSOLUBLE PARTICLES ARE SUSPENDED IN ALIQUID OR GAS .
SOLUBILITYFactors that affect solubility_ nature of the solvent_nature of the solute_temperature
RATE OF DISSOLVING• The rate of dissolving is how fast a substancedissolves in a fixed volume of solvent .TEMPERATURERATE OF STIRRINGSIZE OF SOLUTE PARTICLES
ACIDS AND ALKALIAdjectives : acids- acidicalkali-alkalineSolutions can be sorted by whether they are:acid, alkali or neutral.ACIDS ALKALISSOUR BITTERCORROSIVE CORROSIVETURNS BLUE LITMUS PAPERREDTURNS RED LITMUS PAPERBLUENOT SLIPPERY SLIPPERY (SOAPY FEEL )
CONCENTRATED VS SATURATEDConcentrated acids / alkalisConcentrated – amount of substance variableSaturated – maximum amount of substancein the medium environment .
ACIDS• Acid are soluble in water producehydroxide ions – OH(when dissolved in water)When the oxide of some non-metals dissolve inwater they make an acid. Acids have a sourtaste.They are corrosiveHydrochloric acids Used to remove rust on iron andsteelSulphuric acids Used in car batteries , Remove rustfrom steel objects , makes fertilisers .Nitric acid used to manufacture fertilisers
REACTION OF ACIDS WITH METALSAND CARBONATESAcid + carbonate salt + water+ carbon dioxideFormed bychemicalreactionMetal + Acid Salt + Hydrogenmagnesium + magnesium chloridehydrochloric acid hydrogen
ACIDS IN OUR DAILY LIVESAcids are also present ineveryday livesLemon juice contains citric acid, and vinegarcontains ethanoic acid.Some strong acids are hydrochloric acid,sulphuric acid and nitric acid.Some weak acids are ethanoic acid, citric acidand carbonic acid.
NEUTRALISATIONAcids and alkalis react with each other. Thealkali cancels out the acid in the reaction. This iscalled neutralisation.SALT is made when fromchemical reaction.
NEUTRALISATION IN EVERYDAY LIVESFace tonersFace cleansersShampoosConditionersToothpasteInsect stings
CHEMICAL REACTIONS OF ACIDS1)Acid + Metal salt + hydrogen gas2) Acid + Carbonate salt + carbon dioxide gas + H2O3)Acid + Alkali salt + water*** limewater(slake lime) will turn cloudy , white precipitate produced . Not all metals react with acids (unreactive) Some are very reactive*Hazardous and explosive*Hydrochloric – very strong acid ( CONCENTRATED )*potassium + hydrochloric acid => vigorous
SALTSThe salts of sulphuric acid are known as sulphates.The salts of hydrochloric acid are known as chlorides.The salts of nitric acid are known as nitrates.• The salt made depends on the acid and alkali used.• The salt contains the metal atom from thealkali, and part of the acid molecule.• Reaction of salt with water is known as salthydrolysis
ALKALISMany everyday substances are alkalis.They have a soapy feel (slippery).They are corrosive.When the oxides of some metals dissolve inwater they make an alkali solution.Alkalis react with acids and neutralise them.
ALKALIS IN OUR DAILY LIVESAlkalis are present in many cleaning substances in use in ourhomes.Kitchen cleaners are alkaline because they contain ammoniaor sodium hydroxide, which attack grease.The PH of alkali is greater than 7.Calcium hydroxide and sodium hydroxide are strongalkalis.The most recognisable and common weak alkali isammonia.Ammonia reacts with ammonium salt to produceammonia gas
INDICATORS Indicators helpyou find outwhether asolution isacidic or not.They change colour in acid or alkalinesolutions.All indicator are weak alkaline or weakacid the colour of indicator is due toionic part of indicator.Different indicators change todifferent colours.
LITMUS PAPER• Litmus is an indicator. It changes colour in acidand alkaline solutions.• Different indicator show different colour.• Litmus paper is red in an acid. (Acids turnblue litmus paper red)• Litmus is blue in an alkali.(Alkalis turn redlitmus paper blue)
pH SCALE (INDICATORS)Acids less than 7Alkalis more than 77 is neutralThe lower the number for acids , the stronger the acid .The higher the number for alkalis , the stronger the alkali .
REVISION OF ACIDS AND ALKALIAcids : Corrosive Sour Reacts with blue litmus paper Turns blue litmus paper red Dilute sulphuric acid + magnesium = magnesium sulphate + hydrogen Dilute hydrochloric acid + magnesium = magnesium chloride + hydrogen Dilute acid + Metal = salt + hydrogen Effervescent => bubbly Citric : lemon Formic acid : Insect stings Lactic acid : milk Acid reacts with carbonates to give off carbon dioxide gas Calcium carbonate + dilute sulphuric acid = calcium sulphate + carbon dioxide + water Dilute acid + carbonate = salt + carbon dioxide + water( only with carbonates) Sulphuric acid = in car batteries Nitric acid = in fertilisers Hydrochloric acid = take out rust Dilute acid + carbonate salt + carbon dioxide + water
ALKALIBitterCorrosiveSoapy feelTurn red litmus paper blueAmmonia : fertiliser makerSodium hydroxide (caustic soda ) => detergentsCalcium hydroxide ( slaked lime/limewater) =>reduce acidity in soil in agriculture
IndicatorPH SCALE / RED OR BLUE LITMUS PAPERChanges colour depending on solution tested(acidor alkali ) : definition0-------------7-----------------14Water = neutral ( PH 7 )Acid neutral alkali
HEAT AND IT’S EFFECTS• EXPANSION (GAINS HEAT ENERGY )• CONTRACTION (LOOSES HEAT ENERGY )Countering expansions LEAVING GAPSSolids Expands very little (particles are joined)Liquids Expands more than the solids but less thanthe gases (More particles than gases and a near eachother)Gases Expands most ( Very little particles and arespread freelyBrass contracts/expands more than steel
EXPANSION AND CONTRACTIONSOLIDSSolids expand when heated and contract when cooled . However ,some solids expand so little that we may not even notice theexpansion .LiquidsIf the kettle is filled to the brim with water , the water will spill outwhen it boils because water expands when heated and contractswhen cooled.GasesBefore a loaf of bread is baked, thousands of tiny air bubbles aretrapped inside the dough . As the dough is heated, these bubblesgain heat and expand, creating holes in the bread . This causes thebread to rise . Gases expand when heated and contract when cooled
ROADS AND PATHWAYS(-ve)Excessive expansion on very hot days can causeroads or pavements to crack , or tiles pop-out .To get around with this problem , the tiles onpavements and walls are laid with EXPANSIONGAPS
BRIDGES AND METAL GIRDERSLong bridges sometimes expand up to a meter inhot weather . Without allowance for expansion ,such structures are at risk of damage in very hotweather .Bridges and metal girders on buildings haveEXPANSION GAPS or a free end resting on rollers toallow expansion .* ROLLERS ALLOW BRIDGES AND GIRDERS TOEXPAND OR CONTRACT WITHOUT DAMAGE
WATER PIPESWater pipes and oil pipelines can expand duringhit weather , which might cause them to BURST .Hence , EXPANSION BENDS are made in thesepipes to allow them to expand without anydamage* Expansion bends help prevent damage topipes
TELEPHONE WIRES AND CABLESTelephone wire and cables raised on polescontract in cold weather and become taut , andmay even snap. So , they are STRUNG LOOSELYfrom pole to pole to allow contraction .*Transmission wires must be strung loosely frompole to pole to allow contraction during hotweather.
LABORATORY GLASSWAREIf boiling water is poured into a thick glass , theglass is likely to crack due to the unevenexpansion of the glass . ( THE CG(center ofgravity)OF THE GLASS IS THE AREA WITHHIGHEST GRAVITY , with too much of it at thetop , the glass will TOPPLE).COUNTERING glassware expansion use ofborosilicate / heat-resistant glass.
METAL TYRES(+ve)A metal tyre can be heated up to fit over awooden wheel . When the tyre cools , it clingson very tightly to the rim of the wheel .heat
RIVETSRivets are used to join steel plates and girders.1) When red-hot , the rivet is put into position2) It is then hammered into a head and allowedto cool.3) The contraction on cooling helps to pull thesteel together.
BIMETALLIC STRIPrivetsbrassTHE BRASS EXPANDS MORE (BECOMES BIGGER)than the steel when HEATED . SO , when heated ,the strip bends with the brass on the outside of the curve.WHEN COOLED , the brass contracts more (BECOMES SMALLER ) than the steel . Hence , thestrip bends with the steel on the outside if thecurve .
BRASS AND STEELSteel = iron + carbonBrass = zinc + copper* THESE ARE BOTH METAL ALLOYS ( consists oftwo or more metals )
USES OF A BIMETALLIC STRIP• THERMOSTAT keeps temperature constant :regulates the temperature (HOT/COLD)*examples : used in refrigerators , ovens , air-conditioners. Bimetallic strips are used in thermostats .
BIMETALLIC STRIPSCooling takes place when thetemperature is too cold . Thestrip bends away to break thecontactHeating takes place whenthe current is on . Whenthe temperature is too hot, the strip bends away tobreak the contact .
IN THE REFRIGERATORCOOLING hotter : connectedcolder : not connectedHEATINGCold air stops blowing , refrigerator heats upCONTRACTION-Pulling (inwards)
CONDUCTION• Heat moves from a hotter region to a coolerregion .• Conduction is the process of heat transferthrough a medium or material without anymovement of the medium or materialA material that conducts heat are calledCONDUCTORS but those that do not conductheat are called INSULATORS
GOOD CONDUCTORS OF HEATMost metals are good conductors of heat .However , some conduct better than others .The higher the THERMAL CONDUCTIVITY of amaterial , the better it conducts heat.
CONVECTIONConvection is the transfer of heat from one place toanother by the movement of fluids . A fluid with a givendensity rises within a fluid of greater density and sinkswithin a fluid of smaller density.Convection takes place due to the expansion of fluid. Whenthe fluid (i.e. a liquid or gas ) is hot , its volume increases .This means its density decreases . The less dense fluid thenrises and floats while the denser fluid flows in to take itsplace.
USES AND EFFECTS OF CONVECTIONHousehold ventilationHot air rises and collects under the ceiling . A cool room hasfeatures that let hot air out and cool air in. HOT AIR RISES ,COLD AIR SINKS . If there are no air vents , we can use an airconditioner to keep the room cool.1) The hot air in the room rises to the ceiling2) The air-conditioner cools the hot air , which then sinks tothe bottom of the room.3) More hot air rises and is cooled by the air-conditioner .The cycle repeats itself until the room is cooled .
ELECTRIC KETTLEWhat happens if the heating coil of an electrickettle is placed near the top of the kettle ?If the heating coil is placed near the top of thekettle , the water near the top will start to boilwhile the other parts of the water will remaincool . There will be no circulation of heat .
LAND AND SEA BREEZESLand and sea breezes are caused by convection . (Water us apoor conductor of heat) . During the day , the land is hotterthan the sea . Hot air rises from the land and cool sea breezesblow in to take its place . At night , the reverse takes place .The sea retains its heat and land cools faster.Convection : Mode of heat transfer Convection current : Current flow of heat
RADIATIONRadiation is the method of heat transfer thatdoes not require the presence of matter .. Herefrom the sun radiates across millions of kilometersof empty space . The heat that comes by radiation iscarried by light waves from the sun invisibleinfrared and visible light . This heat is sometimescalled radiant heat.
RADIATIONRadiation is the transfer of heat , in the form of waves (heatwaves) , from one place to another without a medium .HOW A BODY RADIATES HEAT1) Nature of the surface of the body (whether it is black orwhite or coloured , rough or smooth or shiny )The darker and rougher the surface , the more heat it givesout per second .2) Total surface area of a bodyThe greater the area , the more heat per second is radiated.3) Temperature of the body The hotter the body temperature , the more heart persecond is radiated .
Cold air sinksWhere is thefreezercompartmentput in a fridge?FreezercompartmentIt is put at the top,because cool airsinks, so it cools thefood on the waydown.It is warmer atthe bottom, sothis warmer airrises and aconvectioncurrent is set up.
RadiationRadiation travels in straight linesTrue/FalseRadiation can travel through a vacuumTrue/FalseRadiation requires particles to travelTrue/FalseRadiation travels at the speed of lightTrue/False
Emission experimentFour containers were filled with warm water. Whichcontainer would have the warmest water after ten minutes?Shiny metalDull metalDull blackShiny blackThe __________ container would be the warmest after tenminutes because its shiny surface reflects heat _______ backinto the container so less is lost. The ________ containerwould be the coolest because it is the best at _______ heatradiation.shiny metalradiationdull blackemitting
Factors Affecting Radiation1. Nature of surface of body2. Total surface area of body3. Temperature difference between thebody and its surrounding113
Radiation questionsWhy are houses painted white in hot countries?White reflects heat radiation and keeps the house cooler.Why are shiny foil blankets wrapped around marathon runners at the end of arace?The shiny metal reflects the heat radiation from the runner back in, this stopsthe runner getting cold.
Convection questionsWhy are boilers placed beneath hot watertanks in people’s homes?Hot water rises.So when the boiler heats the water, and the hot water rises, the water tankis filled with hot water.Why does hot air rise and cold air sink?Cool air is more dense than warm air, so the cool air ‘fallsthrough’ the warm air.
1. How does heat energy reachthe Earth from the Sun?A. RadiationB. ConductionC. Convection
2. Which is the best surface forreflecting heat radiation?A. Shiny whiteB. Dull whiteC. Shiny blackD. Dull black
3. Which is the best surface forabsorbing heat radiation?A. Shiny whiteB. Dull whiteC. Shiny blackD. Dull black
GLOW STICKHas a glass vial inside the plastic tubeBending the light stick causes the glass vial tobreakThe two solutions mix and undergo a reactioncalled chemiluminiscene , light is emitted .
122What are the changes that can takeplace? Physical changes Chemical changes
123Definition of chemical Reaction• Chemical changes are permanent andirreversible• Produced new substances• Reactants are changed into productsExample:reactant A + reactant B product C + product B
124Definition of physical reaction• When a change is reversible, we call it aphysical change• No new substance is formed
PROCESSESBurning bottled gas for outdoor cooking CombustionIron rusting in the presence of water and oxygen CombinationSugar being heated strongly DecompositionWater being broken down into its elements by electricity ElectrolysisWater puddle slowly disappearing under sunlight Evaporation
126Differences between physical andchemical changesPhysical Changes Chemical ChangesNo new substances formed New substances are formedNo or little heat is taken inor given outHeat and/or light energymay be taken in or given outProperties of substance donot changeProperties of productsdifferent from startingreactants
127between matter and different forms of energy:1. Heat2. Light3. Electricity or by4. Combination of 2 different matterPhysical & chemical changes arebrought about by interactions
1281. Changes in State of Matter2. Combination3. Thermal Decomposition4. CombustionChemical Changes Caused by Heat
129Heat Causes Changes in the State ofMatter• From Solid to liquid to gas or vice versa• Melting, freezing, boiling, evaporation• Sublimation: From solid change straight to gasThese are physical changes since changes arereversible and no new products are formed
130• Some substances undergo sublimation• Like dry ice (carbon dioxide) and iodineSUBLIMATION
131Combination• Combination refers to a process in whichtwo or more substances form a newsubstanceExampleIron + Sulphur Iron SulfideFe + S FeSheat
143Chemical Changes Caused By LightUnder the exposure of light, chemical reactiontakes place with the formation of new productsFading of the colour ofnewspaper due to lightexposure
144Chemical Changes Caused By LightExamplephotographic films : coating of silver bromidesilver bromide silver + brominelight
145Chemical Changes Caused By Light• Does chemical changes take place if a digitalcamera is used?• No, light is changed to electrical signals to formimages in a digital camera.
146• Solar cells are also calledphotovoltaic cells• They convert light energy directly intoelectricityChemical Changes Caused by Light
Solar CellsSolar Panels on House RoofSolar cells are used in areaswhere electricity is notreadily available.Suggests some uses of thisenergy within the house.
148ElectricityThe changes that takes place include:• Heating• Light production• Magnetic effect• Chemical effect• Electrolysis
Heating a light bulb withelectricity to produce light• A physical process• The filament in the light bulb is heated up,and electrical energy is converted to heatand light energy. No new substances areformed149
Splitting water using electricity• This process is called Electrolysis(breaking down of substance usingelectricity )
151Chemical Changes Caused By MixingSodium hypochlorite + water chlorine gas(bleaching)Also used inswimmingpools:
LIGHT CAN BE USEFUL TO US (3 WAYS)Photosynthesis — plants use light to makefood, which in turn gives us food.Photography — light causes chemical changes onphotographic film, giving us photographs.Obtaining energy from solar cells — light isconverted into electricity.
DIFFERENTIATINGProcess ChangeCooking meat ChemicalExtracting aluminum from aluminum ore ChemicalBoiling water PhysicalPhotosynthesis ChemicalExposing photographic film to light ChemicalIodine crystals turning into iodine gas Physical
USEFULNESSUSEFUL NOT USEFULPhotosynthesis RustingCombustion of fuels in power stations Combustion of fuels producing airpollutantsRespiration Forest firesDecay of dead organismsExtracting iron from oreMaking electromagnets electroplatingdigestion
IMPORTANCE OF CHEMICAL CHANGEWhy is the decay of dead organisms animportant and useful chemical change?It returns nutrients back to soil to be recycled for usenaturally by plants, otherwise dead organisms wouldbe found everywhere and there would not be enoughspace on earth to bury them.
ENERGY CHANGES AND HOW THEYWORKi) Furnace --Chemical energy in fuel is changed to heat bycombustion.ii) Boiler -- Heat causes the water particles to have more kineticenergy and turns into moving steam, which has kinetic energy.iii) Turbine --The turbine transfers kinetic energy of the movingsteam to the generator.iv) Generator --Kinetic energy from the turbine turns thegenerator. Kinetic energy of the generator is changed toelectricity.
DEFINITIONSSUBLIMATION- Thermal exothermic (give out / release)- endothermic (take in )OXIDATION- Refers to a process in which a substance reactswith oxygen- Processes such as rusting and combustion areoxidation reactions .
FILMS VS DIGITALLight rays that have bounced off the objectand entered the lens of the camera . Thesource of light is the light shining on thefilms and images will be imprinted on thefilm due to light (reacting with silver bromide).
FILMS VS DIGITALFILMS [CHEMICAL CHANGE]Light energy (from objects) converted intoelectrical energy.DIGITAL [PHYSICAL CHANGE]Electrical signals
SOLAR CELLS• In calculators• Use photovoltaic cells (in photography)They convert light energy directly into electricityLOMOGRAPHY Coloured films
GLOW STICKHas a glass vial inside the plastic tubeBending the light stick causes the glass vial tobreakThe two solutions mix and undergo a reactioncalled chemiluminiscene , light is emitted .
MATERIALS• Grouping and sorting is called classification.• Grouping of objects always helps us to do ourwork efficiently .• Classification of objects can be based onsimilarities and differences .• NON-LIVING THINGS AND LIVING THINGS• MAN-MADE AND NATURAL• Metals, glass , ceramic , plastic , fibre
METALS• Cobalt• Nickel• IronThey have natural ores . Gold , silver … have orestoo!LoadstonesCOPPER OREPlatinum oreLead ore