MATTER IN OUR SURROUNDING
1. Matter is made up of small particles.
2. Matter around us exists in three different states as solid, liquid and gas.
3. Solids are rigid, have definite shape, distinct boundaries and fixed volumes.
4. Solid break under force but difficult to change their shape.
5. Liquids flow and change shape, so they are not rigid but can be called fluid.
6. All organisms breathe in air for their survival.
7. The solids, liquids and gases can diffuse into liquids, the rate of diffusion of liquids is higher that of solids.
8. Gases can be compressed; due to compressibility large volumes of gas can be compressed and transported easily.
9. Liquids, gases exert pressure on walls of container.
10. The temperature at which a solid melts to become liquid at the atmospheric pressure is called melting point.
11. Melting point of ice is 273.16K.
12. The process of melting, change of solid to liquid is called fusion.
13. The amount of heat energy required to change 1kg of a solid into liquid at atmospheric pressure at its melting point is called latent heat of fusion.
14. Latent heat of vaporisation is the heat energy required to change 1kg of a liquid to gas at atmospheric pressure at its boiling point.
15. The phenomenon of change of a liquid into vapours at any temperature below its boiling point is called evaporation.
16. Evaporation causes cooling.
17. Increase in surface area, temperature, wind speed and decrease in humidity are factors affecting evaporation.
18. Sublimation is change of solid to gas and gas to solid without becoming liquid.
19. Change of state from liquid to solid is solidification.
20. Cotton clothes absorb heat from our body, so we wear cotton clothes in summer.
