Question

State whether the following statement is true or false:
All states of matter exert pressure.
A. True
B. False

Answer 1

Hint: Pressure is just perpendicular force acting per unit area of a surface. And all states of matter exert a force on the surface on/in which they are kept. But depending upon state this force could be due to their weight or kinetic energy possessed by their particles.

Complete step by step answer:
First let us understand what pressure is.
Pressure is the thrust acting per unit surface area of a body. Where thrust is the force acting perpendicular to the surface of the body.
Hence,
${\text{Pressure = }}\dfrac{{{\text{Thrust}}}}{{{\text{Area}}}}$
Now, coming to the question indeed all the states of matter whether its solid, liquid or gas exert pressure.
- The only difference is that solid exerts pressure only in down direction due to its own gravitational force/weight.
- While fluids i.e. liquids and gases exert pressure in all directions. It is because since the intermolecular forces are low both in liquids and gases their particles are moving in random motion applying equal forces in all the directions, it means they possess kinetic energy.
- Hence, liquids and gases exert pressure on the walls of the container too in which they are kept. In addition to it liquids also exert a downward pressure on the bottom due their own weight.

So, the given statement is true..

Additional Information:
The SI unit of pressure is Newton per square metre $\left( {N/{m^2}} \right)$or $1N/{m^2} = 1Pa$ (pascal). For a given amount of force smaller the area of application greater the pressure applied and vice-versa.

Note:
Students may think that pressure on a surface due to an object is due to its weight per unit area, so how gases could apply pressure. But the above statement is true for solids only. Actually, pressure is just force per unit area. And we know particles in a gas are in random motion since intermolecular forces are negligible, due to this random motion they have greater kinetic energy and when they collide with a surface, they exert a force. Hence, it can be concluded that gases also exert pressure.