Gases and Pressures

Question 1

A plunger is pushed in, compressing the helium inside the syringe. Suggest why the temperature of the helium might change

Answer 1

The helium exerts a force on the plunger. When the plunger is pushed in, work is done against it. This transfers energy to the kinetic store of the helium particles, which increases the temperature of the helium gas.

Question 2

There is a test tube in a beaker of water. There is a deflated balloon on top of the test tube. If the water is increased to 80°C, why does the balloon start to inflate?

Answer 2

As the water gets hotter, energy is transferred to the kinetic energy store of the particles. The air particles hit the sides of the balloon more often and with more force, this increases pressure. This means that the force pushing outwards becomes greater than the force pushing inwards (air pressure). This causes the net force to push the balloon outwards, causing it to inflate.