Deep Freeze 5
2002-03 MASTER TEACHER NANCY N. MILLER
Teacher Resource Sheet for
Ice Cream Lab
Answers for Analysis & Application Questions
1. What happened shortly after you added the salt to the ice cubes? Was the temperature above or
below the freezing temperature for water? (The ice started to melt as the salt ions broke apart and
interfered with the crystal lattice of the water molecules bonds. The ice water that is formed is
actually below freezing: super-cooled.)
2. What is the only factor that could have caused the changes shown in question 1? What does this tell
you about the freezing point temperature of salt water compared to fresh water? (The breaking of
bonds requires an addition of energy which comes from the ice. The ionic compound breaking down
during the addition of the salt and ice. The freezing point temperature of salt water is less than that
of fresh water.)
3. Heat energy is needed to change phase from a solid to a liquid. List the possible sources of the heat
needed for this phase change in your baggie. Which source do you think is the best possibility and
why? (The ice, the milk, the salt, the air in the baggie, the heat from your hands. The milk is the
best source of heat energy for the melting process because it is a liquid and stores more energy for
the phase change than the air or salt do. Your hands do not touch enough area to be effective
sources of heat.)
4. In looking at the temperature changes shown on your data table, explain how the energy flow of the
baggie system resulted in your tasty treat for an end product. Where is the energy flowing from and
where is it going to? (The energy flows from the milk to the ice. This removes enough energy to
bring about a phase change from liquid to solid.)
5. In the radiator of your car you put a combination of antifreeze and water to keep your car engine
cool in the summer and prevent the radiator from freezing in the winter. Explain how you think this
works in terms of what you saw in the experiment you just did. (The material added in the
antifreeze to the water in radiators interferes with the bonding of water molecules and the formation
of the solid crystal lattice for ice. This will allow the water to stay in a liquid form to circulate
through the engine and absorb the heat from the engine. In the summer, the same material raises
the boiling point of the water and keeps the very hot water from going to a vapor phase. This allows
the water to circulate and absorb even more heat energy from the engine – cooling your motor.)
1.