Matter and Its Composition

Matter is anything that has mass, occupies space and can be perceived by our senses.

The weight of body on moon will be 1 N i.e. [6N x $\dfrac{\text{1}}{\text{6}}$] because the weight of body is $\dfrac{\text{1}}{\text{6}}$ times lighter on the moon than it is on earth.

There will be no change in its mass because mass of a body remains constant irrespective of its place.

(a) When few marbles are put in a glass half filled with water the water level rises up. This is because marble occupy space.

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

The three main characteristics of the particles of matter are:

1. Particles of matter have space between them and this space is called inter-particular or inter-molecular space.
2. Particles of matter are always in random motion.
3. Particles of matter attract each other.

(a) Solid — A solid is that state of matter which has a definite shape and a definite volume. The two examples are gold, wood.

(b) Liquid — A liquid is that state of matter which has a definite volume but no definite shape. The two examples are water, alcohol.

(c) Gas — A gas is that state of matter which has neither a definite shape nor a definite volume. The two examples are hydrogen, oxygen.

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.

(a) The phenomenon of change of one state of matter into another and then back to the original state without any change in its chemical composition, is called interconversion of states of matter. It occurs due to change in temperature and pressure.

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

Solids have negligible intermolecular space as the molecules are closely packed and the force of attraction is maximum. In liquids the molecules are less tightly packed as compared to solids, so the intermolecular space is larger and force of attraction is weaker. In gases the molecules are far apart so the intermolecular space is very large and the force of attraction is the least.

(c) Solids, liquids and gases change their state by change in temperature and by applying pressure.

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.

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.

(a) mass, volume, compressed

(b) atoms

(c) mass

(d) solid

(e) fluids

(a) Melting

(b) Intermolecular force of attraction

(c) Atom

(d) Sublimation

(e) Condensation