1. Define matter.

Ans: Anything that has mass and occupies space is called matter.

2. What is the difference between mass and weight.

3. If an object weighs 6 N on earth what will be its weight on moon. What will be the change in its mass?

Ans: Weight of body on moon =1/6  th of its weight on earth.

∴ Weight of body on moon =1./6  x 6 = 1 N on moon

Mass of a body does not change with change in gravity. So mass of a body will remain the same on moon.

4. Write your observation and conclusion for the following:

(a) When few marbles are put in a glass half filled with water.

(b) Ice is kept at room temperature.

(b) When ice is kept at room temperature, it changes into water. The temperature of ice is lower than room temperature, so it absorb heat from its surroundings and melt to form water.

5. State three main characteristics of the particles of matter.

Answer: Characteristics of Matter

(i) Particles of matter have space between them and this space is called inter-particular or inter-molecular space.

(ii) Particles of matter are always in random motion.

(iii) Particles of matter attract each other.

6. Differentiate between an atom and a molecule.

7. Define:

(a) Solid (b) Liquid (c) Gas

Giving two examples of each type.

(a) Solid: A solid is that state of matter which has a fixed shape, mass and volume. It cannot be compressed,

 e.g. – Sand, Wood, Copper, Ice, etc.

(b) Liquid: It has a definite mass and volume but no definite shape. It takes the shape of the container. It can be compressed to an extent,

 e.g. – Milk, water, ink, etc.

(c) Gas: It is a state of matter which has only definite mass but no definite shape and volume. It takes up the shape of the container

   e.g. – Carbon dioxide, oxygen, etc.

8. Why are liquids and gases called as fluids.

Ans: The substances which can flow are known as fluids. Liquids flow from higher to lower level and gases flow in all directions, so they are called as fluids.

9. (a) Define interconversion of states of matter.

      (b) Why do solids, liquids and gases differ in their physical state?

(c) Under what conditions do solids, liquids and gases change their state.

Ans: (a) The process by which matter changes from one state to another and back to original state, without any change in its chemical composition is called interconversion

Note: It occurs due to change in temperature

(b) Solids, liquids and gases differ in their physical state due to difference in their intermolecular space and intermolecular forces of attraction.

(c) Matter can change from one state to another on changing temperature and pressure.

10. Give reasons:

(a) When a stone is dipped in a glass containning some water the level of water rises but when a spoon of sugar is added to it and stired, the water level does not rise?

(b) A drop of ink added to water in a glass turns whole water blue.

Ans: (a) When a stone is dipped in a glass containing some water, the level of water rises because the stone is a bigger object and cannot be dissolved and adjusted between the intermolecular spaces of water. But when a spoon of sugar is added to it and stirred, the water level does not rise because the sugar particles are smaller and get adjusted between the intermolecular spaces present in water molecules.

(b) A drop of ink added to water in a glass turns the whole water blue because the water and ink particles are always in continuous random motion and due to this motion the blue coloured particles of the ink spread all over and give blue colour to the water.

11. Fill in the blanks:

(a) Air is a matter because it has weight, mass and space and it can be compressed.

(b) The molecules are made up of atoms.

(c) The quantity of matter in an object is called its mass.

(d) The state of matter with definite volume and definite shape is called solid.

(e) The substances which can flow are called fluids.

12. Name the terms for the following :

(a) The change of a solid into liquid. – Melting                                                                                                                                          

(b) The force of attraction between the molecules of matter –   Intermolecular force of attraction

(c) The particles of matter which may or may not have independent existence – Atom

(d) The process due to which a solid directly changes into its vapours – Sublimation

(e) The change of vapour into a liquid- Condensation

13. Classify the following into solid, liquid and gas :

Coal, kerosene, wood, oxygen, sugar, blood, water vapour, milk, wa