a. The table gives the melting and boiling points for lead and oxygen.

i. At 450 °C will the lead be a solid, a liquid or a gas?

ii. At -200 °C will the oxygen be a solid, liquid or a gas?

b. The graph shows how the temperature of a pure substance changes as it is heated.

i. At what temperature does the substance boil?

ii. Sketch the graph and mark with an X any point where the substance exists as both a liquid and gas at the same time.

c. i* All substances consist of particles. What happens to the average kinetic energy of these particles as the substance changes from a liquid to a gas?

ii. Explain, in terms of particles, why energy must be given to a liquid if it is to change to a gas.

Transcribed Image Text:

melting point boiling point in °C in °C lead 327 1744 oxygen -219 - 183