Question

What are the factors responsible for bringing a change in the physical state of a substance?

Answer 1

Temperature and pressure are the two main factors that affect a change in a substance's physical state.

EFFECT OF CHANGE IN TEMPERATURE:

1. When a solid substance is heated, the kinetic energy of its constituent particles increases.
2. This causes the particles to vibrate at a faster rate.
3. In addition, the extra energy allows the particles to overcome the forces of attraction between them.
4. This allows them to move freely and leave their positions.
5. This results in the melting of solid substance and turning into liquid and a liquid substance converts to gas or vapours.
6. The process of converting a solid into a gas and vice versa without passing through the liquid state is known as sublimation.
7. Sublimation involves a change in temperature.

EFFECT OF CHANGE OF PRESSURE:

1. As pressure increases, particles of the substance become closer together, reducing inter-particle spaces, and the physical state of the substance changes.
2. As the pressure increases, the particle's kinetic energy decreases.
3. When pressure is raised further, the gas particles become so close that they attract each other, resulting in liquefaction.
4. Too much compression of gas produces heat.
5. In order to remove the heat produced during compression, it is necessary to cool the gases while applying pressure to liquefy them.
6. The cooling process helps to liquefy the gas during compression.