In physics, pressure is defined as the force exerted on a surface per unit area. When it comes to gases, pressure is created by the collisions of gas molecules with the walls of the container they are in. The concept of pressure is similar to the idea of someone pushing against a wall. The harder and more frequently they push, the greater the pressure.

To understand this better, let's consider an example. Imagine you have a container filled with gas molecules. As the gas molecules move about randomly, they collide with the walls of the container. These collisions create a force on the walls, resulting in pressure. If the number of gas molecules or the speed at which they are moving increases, the frequency of collision also increases, leading to higher pressure.

One common unit of measuring pressure is the Pascal (Pa), which is equal to one Newton per square meter (N/m²). Another commonly used unit is the atmosphere (atm) where one atmosphere is approximately equal to the average atmospheric pressure at sea level (101,325 Pa).

Understanding the concept of pressure in gases is crucial as it forms the basis for several important principles and laws in physics. In the upcoming posts, we will explore the ideal gas law, factors affecting gas pressure, gas laws, and their relationships, as well as various practical applications of gas pressure.