Question

Why are liquids and gases categorized as fluids?

Answer 1

Hint: Fluids are those substances which tend to flow. The tendency to flow depends on the type of intermolecular interaction present between the molecules. There are three states i.e. solid, liquid and gas each has a different type of intermolecular forces.

Complete step by step solution:
- In the given question, we have to explain the reason behind the fluid nature of gases and liquids.
- As we know that there are three states of matter that are solid, liquid and gas.
- Solid is the hardest substance as compared to the gas and liquid this is so because intermolecular force present in solid is so strong that they have the proper shape and size which do not change.
- Moreover, due to the strong intermolecular attraction, the solid cannot be compressed.
- Now, in a liquid state, the intermolecular force of attraction is less as compared to the solid due to which the shape of the liquid is not fixed and changes with change in the container in which it is placed.
- Also, they are definite because they do not expand according to the size and shape of the container.
- Due to the weak intermolecular force attraction they can flow.
- Similarly, in gases, the intermolecular force of attraction is weaker than the liquids and solid due to the gaseous molecules that can flow.
- Gases do neither a definite shape nor definite volume because they attain the shape and volume of the container.

Therefore, due to the weak intermolecular force of attraction between the molecules of liquid and gases, they show the property to flow and are known as fluids.

Note: There are three types of intermolecular interaction that is dipole-dipole interaction, London dispersion force and hydrogen bonds. London dispersion forces are also known as Van Der Waals forces.