A local pool was getting ready for a nighttime pool party. They heated the water to 85o F. When the party started the water felt very warm, but as the night went on it felt cooler and cooler. An employee of the pool decided to record the temperature every half an hour.

Explain why the temperature of the pool was changing.
In your response, be sure to include:

 what happened to the heat that was leaving the pool.
 what must be true of the air temperature based on the recorded pool temperatures.
 why you would or would not expect the graph to look the same if the pool were filled with something other than water, such as mud.