Class 9 Science
Anything that has both mass and volume is called matter. For example – me, you, chair, table, computer, mouse, keyboard, dog, cat, cow, ram, pen, pencil, tree, plant, building, stone, brick, mountain, river, etc.
Early Indian philosopher categorized matter in five types and called them panch-tatwa (Five-elements) - Vayu (Air), Jal (Water), Agni (Fire), Prithvi (Earth) and Aakash (Sky).
According to science matters are divided according to their physical and chemical properties.
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.
Mr. Robert Brown, a Scottish botanist observed the random movement of pollen grains in water in 1827, it is called Brownian motion.
When pollen grains are kept in water, they start giggling rapidly in random order. This is also an evident of motion of particles of matter. Pollen grains moves randomly in water because the particles of water hit the 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 in the mixing of two gases also having different colors. You can observe the dancing particle of dust in the beam of sunlight which is coming through a slit in the room. The particles of dust appear dancing because of its 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 the space between their particles.
When sugar is dissolved in water, the particles of sugar disappear in water. This happens because particles of sugar get adjusted in the spaces between the particles of water. Additionally you will notice that there is no rise of water level takes place when one or two teaspoon of sugar is added in a glass of water, this is because sugar particles get adjusted in the space between the particles of water and no rise in the water level comes in result.
Particles of matter attract each other because of force of attraction.
Force of attraction between particles of matter keeps the particles bonded together. The force of attraction between particles of solid is greatest, between particles of liquid is moderate and between particles of gas is lowest.
Because of the lowest force of attraction between the particles of gas we can move our hand through air easily. To move our hand in liquid, such as water, we have to apply some force, but from a solid such as wood, we cannot move our hand. This is because the force of attraction between particles of gas is almost negligible, in liquid the forces of attraction is moderate but it is greatest in solid.
The force of attraction between particles of solid, liquid and gas can be arranged in decreasing order as follows:
Solid >> Liquid > Gas
Copyright © excellup 2014