Page 103 - Science Class 6 Times Publication

Main Points to Remember

1. Any substance which occupies space and has mass is called matter.
2. Solid, liquid and gas are three states of matter.
3. Molecules are small particles of a substance which can exist
freely and contain all properties of the substance.
4. Atoms are the smallest particles of matter by which
molecules of such matter are composed.
5. The substance which is composed of only one type of atoms
is called element.
6. The substance which is composed of two or more types of
atoms is called compound.
7. The substance which is formed by mixing two or more
substances in any proportion by weight is called mixture.
8. The process of changing of solid into liquid on heating is
called melting.
9. The process of changing of liquid into gas on heating is
called evaporation.
10. The process of changing of liquid into solid on cooling is

called solidication or freezing.
11. The process of changing of gas into liquid on cooling is called
condensation.
12. The process of changing of solid into vapour on heating and
vapour back to solid on cooling is called sublimation.

Exercise

1. Choose the best alternative in each case:

a. Which of the following sentences is incorrect about matter?
i. Matter has mass.

ii. Matter occupies space.

iii. Matter is made of atoms or molecules.

iv. Matter can be seen.

Times' Crucial Science and Environment 99 Book 6