How can the state of matter be changed?
Matter can be changed from one state to another by:
(i) Change in temperature
Increase in temperature changes the state of matter from solid to liquid and liquid to gas.
For example, when ice is subjected to heat, it melts and turns into water. When water is heated, it evaporates and turns to vapour.
Let us understand this in detail.
Particles in solids are compressed and tightly bound. The forces of attraction between these particles are strong enough to hold them together and prevent them from moving around.
When heat is applied, the kinetic energy in these particles increases. They start to vibrate and when the energy in the particles is greater than the forces of attraction, the particles break free of each other. Hence, they move from their fixed positions.
This increases the space between the particles and state of the matter changes from solid to liquid.
Similarly, applying heat changes a liquid into gas.
Effect of temperature on states of matter
Decrease in temperature changes the state of matter from gas to liquids and liquid to solid.
For example, when water vapour is cooled, it changes to water. And water is cooled to a certain temperature, it freezes to form ice.
(ii) Change in pressure
Since gases are highly compressible, applying pressure can change their state from gaseous to liquid.
Due to pressure, the gas particles are brought in close contact with each other. The attractive forces eventually become strong enough to hold the particles close together, and the gas condenses to the liquid state. And further compression changes the liquid into a solid form.
Effect of pressure on states of matter
For example,
Compressing and cooling gaseous carbon dioxide under high pressure produces liquid carbon dioxide, which when applied with pressure changes to a solid, also known as dry ice.