1. Anything, that has a mass and occupies space, is called matter.
  2. The common states of matter are solid, liquid and gas. Gases have neither definite shape nor volume, liquid has definite volume but no definite shape, whereas solid has definite shape as well as definite volume.
  3. Liquid takes the shape of vessel in which it is kept, but does not occupy total volume available, whereas gas takes the shape of vessel as well as occupies all the space available to it.
  4. According to kinetic molecular theory, matter is composed of particles, which are called molecules. Molecules are in motion and they possess kinetic energy.
  5. The three states of matter depend upon arrangement, motion and forces of attraction between their particles.
  6. In solids molecules are tightly packed with one another and they perform only translational motion. Due to this, molecules in solid neither slip nor slide over one another, hence shape and volume of solid is definite.
  7. Interconversion of three states of mate are common and they may be seen by us, just like change of ice to water, evaporation of water and sublimation of iodine, ammonium chloride and napthaline.
  8. During melting, solids are converted into liquids and in this process movement of particles overcome the intermolecular attractive forces.
  9. Certain solids are directly converted into gaseous state during heating and this process is called sublimation.
  10. In gaseous state, molecules are widely separated from one another and they move freely in all direction; hence the shape and volume of gas are not fixed.
  11. When vapour pressure of a liquid becomes equal to external pressure, then it starts boiling and the temperature is called the boiling point. During boiling bubbles of vapours are able to form within the bulk of liquid and then rise to the surface, where they burst and release vapours. In other .words in this way liquid is converted into gas.
  12. At boiling point the temperature of liquid remains same until all of the liquid is vapourized to gas. This change is called as vapourization or evaporation.


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