Chemistry 30 Thermodynamics: Heating and Cooling Curves

Overview:

In this lab you will measure the temperature of a sample of a substance every 30 sec as it undergoes changes of state from liquid to solid (freezing) and then from a solid to liquid (melting).
You will graph the data for both the heating and cooling curve (on the same graph). Make a prediction - what do you think the heating and cooling curves will look like?
If you are able to carry out the experiment, your teacher will provide you with a detailed procedure to follow.
Sample data is provided in the links above if you are unable to actually carry out the lab.

Web Links

General Chemistry: Principals and Modern Applications Prentice Hall (publisher). An excellent short movie explaining the heating curve of a substance.
http://cwx.prenhall.com/petrucci/medialib/media_portfolio/text_images/031_ChangesState.MOV
http://netcamp.prn.bc.ca/nuggets/heatingcurve.swf - A flash animation of the heating curve of water, from the solid state to the gaseous state. (You don't need to worry about the formulas shown at the end of the animation)

Related Issues and Practical Applications:

Perspiration - heat from your body is used to convert moisture on the skin to gaseous water, causing your body temperature to lower
Refrigeration and air conditioners work by removing heat from the surroundings to cause the evaporation of a coolant such as freon or ammonia
Farmers often protect their crops from frost damage by spraying water onto their crops; as the water freezes it releases heat which helps protect the plants.

Chemistry 30