Question: The density of the atmosphere decreases with an increase in the height above sea level (altitude).  What would happen to the atmosphere as Jim climbed lower down a mountain it would become less dense or it would become more dense?
Answer: it would become more dense

Question: The particles in matter are always moving. The more energy they have, the faster they move.  When a child has a lot of energy they will move around slower or faster?
Answer: faster

Question: The more energy the particles in matter have, the faster and more strongly they vibrate.  Don wants to make sure that his particles will move slower, so he will make sure the energy they have is more or less?
Answer:
less