Class 9 Science

# Matter In Our Surroundings

Anything that has both mass and volume is called matter. You can also say that anything which has mass and which occupies space is called matter.

Examples: chair, table, computer, mouse, keyboard, dog, cat, cow, ram, pen, pencil, tree, plant, building, stone, brick, mountain, river, etc.

Early Indian philosopher categorized matter into five types and called them panch-tatwa (Five-elements). They are as follows:

1. Vayu (Air)
2. Jal (Water)
3. Agni (Fire)
4. Prithvi (Earth)
5. Aakash (Sky)

In this lesson, you will learn about physical nature of matter.

## Physical Nature of Matter

• Matters are made of particles.
• The particles of matters are very small.
• The particles of matter are moving continuously.
• Particles of matter have space between them.
• Particles of matter attract each other because of force of attraction.

### Matter is made of particles

All matters are made of particles. These particles are very small and cannot be seen by naked eyes. For example a drop of water contains about 1021 particles of water.

### Particles of matter are very small

Particles of matters are very small. They cannot be even seen using a simple microscope.

When a teaspoon of salt is dissolved in one or two litre of water, every drop of that water tastes salty. It happens because a teaspoon of salt contains numerous particles of salt.

When few drops of dettol are mixed in water, the whole water gives the smell of dettol. Even after diluting this dettol mixed water, it gives the smell of dettol. It happens because of numerous particles of detool.

This proves that particles of matter are very small.

### Particles of matter are moving continuously

This can be proved by putting a small crystal of potassium permanganate in water. When you will put a small crystal of potassium permanganate in water in a transparent glass, you will see that the purple thread like structures start mixing with water and after some time all water becomes purple. The thread like structure is made by motion of the particles of potassium permanganate, when these particles start mixing with water. At the end, the whole water turns of magenta colour because of motion of particles of potassium permanganate.

When you put a spoon of salt or sugar in a glass of water, it dissolves in water after some time. This happens because of the motion of particles of sugar, salt and water.

Mixing of gases in nature is also the evidence of motion of particles. While sitting in the drawing room, you get the aroma of our favourite food, while food is being cooked in the kitchen. This happens because vapor coming out from the hot food mixes with air and travels to your nostrils. It happens because of the motion of particles.

This proves that particles of matter are continuously in motion

## Brownian Motion

Mr. Robert Brown, a Scottish botanist observed the random movement of pollen grains in water in 1827.

When pollen grains are kept in water, they start giggling rapidly in random order. This is an evidence of motion of particles of matter. Pollen grains moves randomly in water because particles of water hit pollen grains from all sides in a random manner.

Pollen grains move faster in warm water, because particles of warm water move more rapidly.

Brownian motion can be observed during mixing of two gases having different colors.

You can observe the dancing particle of dust in the beam of sunlight coming through a slit in the room. The particles of dust appear to be dancing because of their continuous motion along with the particles of air.

Brownian motion proves that matters are made of very small particles and they are moving continuously.

Particles of matter have space between them. Gas can be compressed a lot because of lot of space between their particles.

When sugar is dissolved in water, the particles of sugar disappear in water. This happens because particles of sugar get accomodated in the spaces between the particles of water. Additionally, you will notice that there is no rise of water level when one or two teaspoon of sugar is added in a glass of water. It happens because sugar particles get accomodated in the space between the particles of water and water level does not rise.

### Particles of matter attract each other because of force of attraction

Force of attraction between particles of matter keeps the particles bound together. The force of attraction between particles of solid is the greatest. The force of attraction between particles of liquid is moderate and that between particles of gas is the lowest.

You can easily move your hand through air because of the lowest force of attraction between the particles of air. You can move your hand through water not so easily because of somewhat less space between particles than what is in case of air. But you cannot move your hand through a wall or a brick because of negligible space between particles in solids.

The force of attraction between particles of solid, liquid and gas can be arranged in decreasing order as follows:

Solid > Liquid > Gas

## Quiz

See Answer

1: (c) Five, 2: (a) Particles, 3: (d) Millions, 4: (a) Greatest, 5: (b) Negligible, 6: (c) Lowest, 7: (a) Chalk, 8: (c) Air, 9: (b) Book, 10: (d) Air