As we look at our surroundings, we see a large variety of things with different shapes, sizes and textures. Everything in this universe is made up of material which scientists have named “matter”. The air we breathe, the food we eat, stones, clouds, stars, plants and animals, even a small drop of water or a particle of sand – every thing is matter. We can also see as we look around that all the things mentioned above occupy space and have mass. In other words, they have both mass* and volume**.
1.1.1 MATTER IS MADE UP OF PARTICLES
For a long time, two schools of thought prevailed regarding the nature of matter. One school believed matter to be continuous like a block of wood, whereas, the other thought that matter was made up of particles like sand. Let us perform an activity to decide about the nature of matter – is it continuous or particulate?
1.2.1 PARTICLES OF MATTER HAVE SPACE BETWEEN THEM
In activities 1.1 and 1.2 we saw that particles of sugar, salt, Dettol, or potassium permanganate got evenly distributed in water. Similarly, when we make tea, coffee or lemonade (nimbu paani ), particles of one type of matter get into the spaces between particles of the other. This shows that there is enough space between particles of matter.
Observe different types of matter around you. What are its different states? We can see that matter around us exists in three different states – solid, liquid and gas. These states of matter arise due to the variation in the characteristics of the particles of matter.
We all know from our observation that water
can exist in three states of matter–
• solid, as ice,
• liquid, as the familiar water, and
• gas, as water vapour.
Do we always need to heat or change pressure for changing the state of matter? Can you quote some examples from everyday life where change of state from liquid to vapour takes place without the liquid reaching the boiling point? Water, when left uncovered, slowly changes into vapour. Wet clothes dry up. What happens to water in the above two examples?