IGCSE Thermal Physics Worksheet

Questions 1) Why are there three states of matter? 2) How can a solid evaporate? 3) Why do liquids cool when they evaporate? 4) Why does it take time for a solid to melt? Why does it not change instantly into a liquid? 5) Why does it take longer to boil a liquid than to melt a solid? 6) Why do diff erent substances melt at diff erent temperatures? 7) Why do diff erent substances have diff erent boiling points?

The picture shows an experiment to investigate how the volume of a gas depends on its pressure. The cylinder contains nitrogen gas. Pushing in the piston increases the pressure, as shown on the gauge. The volume of the gas can be read from the scale, to the nearest 1 cm3. The table shows the results from the experiment.

Pressure, p/kPa 75 90 105 120 135 150

Volume, V/cm3 26 22 19 16 14 13

p×V

8) Copy the table and add a third column. In the third column, add values of p × V. Does this value appear to be constant, as suggested by Boyle’s law? 9) Plot a graph of V against p. Use it to deduce the volume of the nitrogen gas at atmospheric pressure (100 kPa). 10) During the experiment, the experimenter changed the pressure on the gas and then waited for a short while until the volume of the gas fell to a steady value. Explain why this was necessary. 11) A tank contains 120 m3 of air at atmospheric pressure (100 kPa). It is submerged in water to a depth where the pressure is 450 kPa. What will its volume become at this pressure? (Assume that the air obeys Boyle’s law.) 12) A cylinder of oxygen gas contains 400 cm3 of air at a pressure of 20 atmospheres. If the oxygen is released so that its pressure falls to 1 atmosphere, what volume will it occupy?