Question

Name two substances which expand on heating.

Answer 1

Hint: There are four states of matter: solid, liquid, gases and plasma. Matter has states. Use the concept of thermodynamics. Almost all substances expand on heating. Take daily examples to understand easily.

Complete Step-by-Step solution:
We all know that there are many substances which expand on giving heat to them. As thermal expansion is a tendency of a material to change its state or characteristic due to external temperature. Almost all material expands in this universe. Two examples are water and air since their density decreases and volume increases and hence expansion takes place.
Therefore two examples are:
1. Water
2. Air
The main reason for expansion on heating is, when we give heat to material particles in the material get excited about taking energy because heat will work as energy. After taking energy, it gets unstable and tries to move and try to get away from each other.
In a case of solid if particles are very compact to each other then it is hard for particles to move from one place to another. While in liquid, particles in liquid are little free from each other, hence it is less dense. While in gases, particles are very much free and hence it is less dense. And energy required i.e. heat required is less in case of gases. Gases expanded most on heating and solid are the least because gas particles are already free apart and are much more free to move. There are many substances which expand on heating and get contact on cooling.

Note: Remember the state of matter. Memorise on what basis they are classified. Plasma is the fourth state of matter, which lies between liquid and gases. Particles/constituents in the substance play an important role.