Physical n Chemical Changes

CHAPTER 5: ENERGY AND CHEMICAL CHANGES5.1 Physical and chemical changes

Introduction Living thing Non-living thing Both living and non-living thing are matterMatter around us undergoes changes. These changes can be classified into two types - physical changes - chemical changes

Physical changes Physical changes in a substance is one that effect its physical properties, such as

ShapeVolumeDensityState of matter (solid,liquid,gas)ColourMass

Physical changes No new substance is form during a physical change.Physical changes are usually reversible. This mean that the physical properties of the substance which has undergone a physical change can be changed back.

Watericewater

Physical changes Examples

Changes of physical stateCaused by heating Steam watericeCaused by cooling No new substance form because H2O remain H2O

Physical changes Dissolving a solid in waterSugar + wateraqueous sugar ( larutan gula)Reverse changesAqueous sugar sugar + water evaporateddissolvedAqueous sugar sugar + water distillation

Physical changes Crystallizing a salt from it saturated solution

Saturated salt means a solution with maximum quantity of the salt dissolved on it.Solid salt can be obtained by crystalization

Changes of matter that produce new substanceThe new substance have chemical properties which are different from the original substance Chemical changes are usually difficult to reverse. This means that the product formed cannot be easily changed back into the reactantChemical Changes

Chemical ChangesBurning of paper

Example Paper ash + carbon dioxide Burn butAsh + carbon dioxide Cannot bepaper

Chemical ChangesBrowning of a peeled apple

Peeled apple browning appleExposed to air

Chemical ChangesCombustion of feul

Hydrocarbon + oxygen carbon dioxide + oxygen

Chemical ChangesPhotosyntesis

Carbon dioxide + water glucose + oxygenlight(in plant)

Examples in daily life

Physical changes in daily lifeChemical changes in daily lifeFreezing of water to form ice cubeBoiling an egg to get a hard-boiled eggBoiling of water Burning of fossil fuel in motor vehiclesDissolving sugar or salt in water Respiration in living organismMelting of wax to form different shapes of candlesDecomposition of fallen leavesMelting of chocolateDigestion of food in our bodyEvaporate of sweatPhotosynthesis in green plants

Comparison between physical and chemical changes Physical changesChemical changesDIFFERENCESIn term of

No Formation of new substanceYes reversibleReversibility Difficult to reverseLess energy is neededAmount of energy requiredMore energy is neededChanges in physical properties onlyChange in properties Changes in chemical and physical properties

SIMILARITIESSubstance in both processes undergo changesBoth changes require energy

Test yourselfA reaction takes places and the product is different that what you started with.

Answer: Chemical change

Test yourselfTearing a piece of paper into 100 pieces

Answer: Physical change

Test yourselfHammering a nail into a piece of wood


Test yourselfBaking a cake


Test yourselfMixing red and green marbles


Test yourselfCombustion of wood


Test yourselfDissolving sugar with water


Test yourselfChopping wood


Test yourselfYou combine two clear liquid and they turn to cloudy white


Physical n Chemical Changes

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