What is physical change?Some facts about the physical changes are

NDA / Chemistry 🧪 Lesson 01 PHYSICAL AND CHEMICAL CHANGES.

Generally 1-2 questions are asked from this chapter. Questions from this chapter are mostly based upon the Fact about physical and chemical changes.

There are some changes during which no new substances are formed whereas during some other changes new substances are tormed.Therefore on this basis we can classify all the changes into two groups- physical changes and chemical changes.

1. Physical change 

A physical change is a change in which the composition of a substance is not affected, i.e. no new substance is formed. e.g. Interconversion of states is a physical change because these changes occur without a change in composition and no change in the chemical nature of the substance. When an ordinary piece of iron is magnetised in the presence of a strong magnetic field.Here the colour,density mass and the composition remains the same.

Hence,magnetisation is a physical change.The physical changes are reversible. Magnetisation can be reversed by heating the piece of iron.

Evaporation,distillation,sublimation,

condensation and crystallisation are examples ol physical changes.

The blue colour of copper sulphate crystal disappears when it is heated strongly because on heating water of

crystallisation of crystal is lost.It regains its blue colour when moistened with a drop of water.

                    (Heat)

CuSO4.5HO------> CuSO4+5H2O

    (Blue)                   (White)

It is an example of a physical change.

Some facts about the physical changes are.

(i) Physical changes are temporary and reversible.

(ii) Composition of the constituent of matter remains same during physical change i.e. constituent particles of matter does not change.

(iii) Physical changes are due to the change in physical properties like density, volume, state temporarily.

Note

•Amount of space that a substance or object occupies is called volume of that substance.

•Density is the degree of compactness of a substance.It is defined as mass per unit volume.

                

 Density=Mass/Volume

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