Cambridge O Level Chemistry · Syllabus 5070 · States of Matter
Gas pressure
What is Gas pressure?
The effect produced by the particles of a gas colliding with the walls of its container. Each collision exerts a small force on the wall, and the pressure depends on how often those collisions happen and how forcefully. Raising the temperature of a gas makes its particles move faster, so they collide with the walls more often and more forcefully. If the container can change size the boundary is pushed outward until the pressures balance and the volume increases; if the container is rigid the volume cannot change and the pressure of the gas rises instead.
This definition is part of the States of Matter chapter in Cambridge O Level Chemistry.
Questions students ask about Gas pressure
Why does a gas exert pressure, and why does the pressure rise when the gas is heated?
Gas pressure is caused by the gas particles colliding with the walls of their container; each collision exerts a small force on the wall. Heating the gas makes its particles move faster, so they collide with the walls more often and more forcefully. If the container is rigid, the volume cannot change and the pressure rises. If the container can expand, such as a balloon or a free syringe plunger, the volume increases instead. Always state what the container is doing before you write the answer.