Problem 2 - The mass of Earth is 6.0x1024 kg. The mass of a hydrogen atom is 1.6x10-2 kg. If the entire mass of the shell were evenly spread out in a sphere with the
shell's radius, how many hydrogen atoms would you expect to find in a cubic meter of
this shell to the nearest 10,000 atoms?

has diffused more quickly, so it must be a

lighter gas. Its particles have greater velocity

than the particles of Y at the same temperature.

(Note though that they will both have the same

value for average kinetic energy.)

7 From the kinetic molecular theory we would

expect a solid to be more dense than its liquid,

and therefore that ice would sink in water.

8 Bubbles will be present through the volume

of the liquid. A brown gas is visible above the

brown liquid. As the two states are at the same

temperature, the particles have the same average

kinetic energy and are moving at the same

speed. The inter-particle distances in the gas are

significantly larger than those in the liquid.

9 At certain conditions of low temperature and low

humidity, snow changes directly to water vapour

by sublimation, without going through the liquid

phase.

10 Steam will condense on the skin, releasing energy

as it forms liquid at the same temperature (E–D

on Figure 1.4). This is additional to the energy

released when both the boiling water and the

condensed steam cool on the surface of the

Explanation: