Do we have to make changes every time in the temperature and pressure to change the state of a matter? Explain.

Yes, we do have to change the temperature and pressure to bring a change of state. Because the change in state occurs only when any one or both of temperature and pressure changes. The effects of temperature and pressure in the change of state are as given below:

• Effects of change of temperature on the matter: On increasing the temperature of solids, the K.E of the particles increases.Due to the increase in K.E, the particles start to vibrate with greater speed. The energy supplied by heat overcomes the force of attraction between the particles, and they start moving freely. A stage comes where solid melts and is converted into a liquid. And the further same process continues and converts into gas.

Example: Ice→ Water→ Gas.

• Effect of change of pressure on the matter: By applying pressure, we can bring the particles of matter closer and closer to each other. So by applying pressure, gas can be converted into solid and by decreasing pressure solid can be converted into gas.

Example: Dry Ice → CO₂