Question

How does matter change from solid to a liquid to a gas?

Answer 1

Hint: For the interconversion of matter from one state to other kinetic theory of gases is used. According to kinetic theory, to convert a solid to liquid and to a gas we have to decrease the strength of interparticle forces of attraction. To bring about a change we need to supply thermal energy to the substance.

Complete step by step answer:
Step 1: A solid is a substance which has fixed shape and volume and that is free from any internal cavity. The interparticle spaces in solids are negligible and interparticle forces are strongest.
Step 2: Conversion of a solid to a liquid:
Liquids do not have a fixed shape and volume, they take the shape of the container in which it is poured. The interparticle spaces are more in liquids therefore interparticle forces are weaker as compared to that of solids.
$$Interparticledis\tan ce\propto {\displaystyle \frac{1}{Interparticleforces}}$$
To convert a solid into liquid we need to decrease the strength of the bond. This can be achieved by heating the substance. When we heat a substance the kinetic energy of particles increases and they start moving randomly. Ultimately distance between particles increases and forces of attraction decreases and the state of matter is converted to liquid. The process is known as melting. Eg.
$Ice(s)\to Water(l)$
Step 3: Conversion to a gas:
Case 1: Liquid to gas: This can be achieved by supplying more of thermal energy to the substance to bring about desired change. This process is known as vaporization. In vaporization two processes are included Boiling and Evaporation.
Boiling: Boiling is a rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point so that a liquid changes to its vapour state. Eg.
$Water(l)\to WaterVapours(g)$
Evaporation: Evaporation is a slow vaporization that occurs on the surface of a liquid and changes it into a gas phase. It occurs at any temperature lower than its boiling point. Eg. Drying of clothes, cooling of water in earthen pots.
Case 2: Solid to gas: When a substance (matter) absorbs enough heat from the surrounding and changes from solid to gas without passing through the liquid state, the process is known as sublimation. eg. Moth balls (Naphthalene balls) will sublime.


Note: Interconversion from one state to another can be achieved by supplying heat to the substance or by withdrawing the heat from the substance. Heating a substance increases the kinetic energy of particles and they start moving randomly, the interparticle forces of attraction decrease and their state changes.