Question

What is a ‘phase transition’? Using water as an example explain the major differences between the three physical states (phases) of water.

Answer 1

Phase transition is when a substance change from a solid, liquid or gas state to a different state at specific combination of temperature and pressure.

The phase for water is in three form

1. Solid state (ice)
2. Liquid state (water)
3. Gaseous state (steam)

Phase transition occur either from a solid state to liquid state on the application of heat and on continuous application of heat, the liquid state of water changes to a gaseous state at specific temperature and pressure

Ice ⇒ Water ⇒ Steam

(solid) (liquid) (gas)

The major differences between these states are explained below:

Solid state:

1. This state has a fixed shape, which cannot change easily,
2. It also possesses a form of structural firmness.
3. The energy level of solid substances is at the lowest.
4. There also exist very little motion of molecules within the solid substance.
5. Lastly, the speed of sound is fastest compared with the other phases of water.

Liquid state:

1. The liquid state of water does not possess any shape or rigidness,
2. it flows freely.
3. Unlike the solid state that has a shape and volume, the liquid state has only volume but no shape.
4. The energy level of the liquid state is at medium
5. Molecules move in Brownian motion
6. Sound speed is slower than solid state but faster than the gaseous state.

Gaseous state:

1. It does not have any shape but adjusts according to the shape of whatever it is put in.
2. It does not have a definite volume.
3. The energy level is at the highest
4. The movements of molecules are random, constant and free.
5. Sound moves the slowest in this state when compared to the other states.