Here’s how thermal expansion affects pressure in closed containers:
When you have a closed container with a gas inside, the gas molecules move and collide with the container walls, creating pressure. If you increase the temperature, the gas molecules gain more kinetic energy and move faster.
Thermal expansion generally refers to materials increasing in size when heated, but in this context, the main factor is the gas expanding due to temperature rise.
- If the container is rigid and fixed in volume (like a steel can), the gas cannot expand because the container’s size is fixed.
- As temperature increases, the gas molecules move faster and hit the walls more frequently and with more force, so pressure inside the container increases.
This relationship is described by the ideal gas law: PV=nRTPV = nRT
where:
- PP = pressure,
- VV = volume,
- nn = amount of gas,
- RR = gas constant,
- TT = temperature (in kelvins).
If VV is constant (closed, rigid container) and nn is fixed (no gas escapes), then increasing TT leads to an increase in PP.
If the container can expand (like a balloon or a flexible container), the volume VV increases with temperature due to thermal expansion of the container material. This volume increase can partially offset the pressure increase because the gas has more space to occupy.