Experiment of the Week - A Cool Change - 4/06/09
the newsletter experiment, we are going to look into the sciences of
chemistry and energy. It may seem strange to be looking into two
different areas of science, but it is not unusual for the areas of
science to overlap. You will need:
glasses of water
- epsom salts
- a spoon
the two glasses of water on the table, and let them sit for a few
minutes. Use the thermometer to check the temperature of both
of water. You want them both to be the same temperature.
place a tablespoon of epsom salts into one of the glasses of water, and
stir. Wait a minute and then test the temperature of the two
again. Are they still the same?
probably found that the water with the epsom salts is a little
Wait another minute and test it again. It should be even
a period of a few minutes, I found that the temperature of the water
with the epsom salts dropped over two degrees. Why?
is tied to energy. Whenever something changes, energy has to be
involved, and that includes chemical processes. We often think of
chemical reactions as giving off heat, and many of them do. These
changes are exothermic, meaning "outside heating", because they give
sometimes a change can be endothermic, which means that heat is
absorbed from surrounding materials, making them cooler.
formula for epsom salts is MgSO4·7H2O.
it dissolves in water, it separates into magnesium ions (Mg) and
sulfate ions (SO4).
For them to separate, they need to absorb some energy, in this case
heat energy, which is absorbed from the surrounding water, making it
same thing happens with other chemicals, including ammonium nitrate,
which is used in "instant cold" packs. With cold packs, you
water. The ammonium nitrate is endothermic as it dissolves in
and the pack gets cold enough to sooth an injury.