UKPCS Science Chemistry: Physical change and Chemical change #41

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Comparison Chart- Physical change and Chemical change

BASIS FOR COMPARISONPHYSICAL CHANGECHEMICAL CHANGE
MeaningPhysical change refers to a change in which the molecules are rearranged but their internal composition remains same.Chemical Change is a process in which the substance transforms into a new substance, having different chemical composition.
ExampleTearing of paper, melting/freezing of water, cutting of trees, etc.Burning of wood/trees/paper, rusting of iron, setting of curd, etc.
NatureReversibleIrreversible
Original matterCan be recoveredCannot be recovered
InvolvesChange in physical properties of the substance, i.e. shape, size, color etc.Change in chemical properties and composition of the substance.
Product FormationNo new product is formed.New product is formed.
EnergyAbsorption and evolution of energy do not take place.Absorption and evolution of energy take place, during reaction.

 

Example of both changes occurring simultaneously:

  • Burning of candle: While melting of wax is a physical change, as the state of the substance changes from solid to liquid, burning of wax is a chemical change, as after consuming energy from wax, light lits up.
  • Cooking of food: Cooking of raw vegetables or grains is a chemical change and transformation of water into steam is a physical change.

Conclusion

To sum up, physical change is any change that only transforms the substance’s physical properties, but chemical change results in the change in the chemical structure of the substances involved.


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