National Aeronautics and
Goddard Space Flight Center
Aqua background information
FOR THE CLASSROOM†††††††
Conservation of Energy and Phase Change of Water
Adapted from the Institute for Global Environmental Strategies
Water is the primary energy mover on Earth. Waterís high
specific heat allows it to transport energy (in the form of heat) in the Earthís
atmosphere and oceans. Both liquid water and water vapor can transport energy
over great distances, for instance through ocean currents and winds. In this
exercise, we look at the energy absorbed by water needed to produce phase
changes from ice to liquid.
Bunsen burner; ring stand with wire screen; ring; 250 mL
beaker; goggles; beaker tongs; pencil & paper; graph paper; thermometer;
stopwatch; plastic stirrer; ice; water.
the ring to the ring stand and place the Bunsen burner under the center
of the ring. Adjust the ring so itís 3-5 cm above the top of the Bunsen
burner and place the wire screen on top of the ring.
your goggles on. Take the Bunsen burner out from under the wire screen and
light the burner when directed to do so by your instructor. Adjust the gas
so that you have a small flame. Adjust the air holes until the flame is
no longer yellow in color.
150 mL of ice in the beaker and add 50 mL of water.
the plastic stirrer, stir the water and ice mixture. When it reaches the
lowest temperature, record the temperature on the chart.
beaker tongs, place the beaker on the ring stand and start the stopwatch
simultaneously. Begin recording the temperature every 30 seconds for at
least 15 minutes. Continuously stir the ice/water mixture.
the time when the ice begins to melt, when all the ice is gone, and when
the water begins to boil.
the data placing the temperature on the vertical axis and the time on the
horizontal axis. Mark the points where the water was changing phase.
to your graph, did the temperature change during the phase changes?
was the temperature change most rapid? (Refer to the slope of your graph.)
If the Bunsen burner output was constant, what can you infer about the absorption
of energy by the water?
phase change required to most energy to achieve?
can you infer about the release of energy by the water when it reverses
the direction of phase change? (Vapor to liquid to solid)
Image rendered by Reto Stockli, based on a prior image
by TRW. Text by C. Parkinson, Aqua Project Scientist, Goddard Space Flight