Fig. 1 shows a hand pump being used to inflate a bicycle tyre. The pump is held still while the handle is pushed down. Air enters the tyre through a valve. ...
Question 1 Report
Fig. 1 shows a hand pump being used to inflate a bicycle tyre. The pump is held still while the handle is pushed down. Air enters the tyre through a valve. After several pushes, the tyre feels firm and supports the cyclist's mass. The air inside remains a gas, although its volume in the pump becomes much smaller during each downward push. No new air particles are made during the compression in the pump.
(a) Describe what happens to the volume of air in the pump when the handle is pushed down. [1]
(b) Use the particle model to give two reasons why the pressure in the pump increases. [2]
(c) Give the name of the process by which gas particles spread through the tyre after entering it. [1]
(d) How does increasing the number of air particles in the tyre help it support the cyclist? [2]
(e) Draw a particle diagram to show air in the pump before compression and after compression. [2]
Answer Details
(a) When the handle is pushed down, the volume of air in the pump decreases. [1]
(b) The same number of particles occupies a smaller volume [1], so collisions with the pump walls are more frequent. [1] This increases pressure.
(c) Gas particles spread through the tyre by diffusion. [1]
(d) Adding air means more particles collide with the tyre walls. [1] This gives greater pressure, pushing the tyre outwards and making it firm enough to support the cyclist. [1]
(e) Before compression the particles are randomly spread through a larger space. After compression, the same number are randomly arranged in a smaller space and are closer together. [2]
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