Explain without the key

describe: give the features or what happens. explain: give reasons and connect them to evidence. predict: use the information to say what you expect.

A sealed glass tube, 100 cm long, is full of still air. A small puff of a scented gas is let in at its left end. Four sensors, A to D, measure the concentration of the scented gas, all on the same scale (no units). The table gives each sensor's distance from the left end and two sets of readings. (a) Describe how the concentration along the tube changes between the two sets of readings. (b) Explain, using kinetic particle theory, why the concentration falls at sensor A but rises at sensor D. (c) Predict what all four sensors would read in the end, after a very long time. State whether the gas particles are still moving then.