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Evangelyn Lilly William H. Ray
5639 Kimbark Ave.
Chicago IL 60637
a. To show when water freezes at a temperature of 0oC (32oF), it turns into
b. To show that the water level remains the same before and after the ice has
c. To explain that ice melts at 0oC (32oF).
d. To demonstrate how ice can be melted without heating it.
e. To show that increased pressure lowers the melting point of ice.
ice cubes, food coloring, two rocks, a glass, wire, pan, cups, salt
metal forks or spoons, and plastic pop bottles
Introduce Frozen Solids:
a. Float an ice cube in a glass of water, mixed with food coloring. Mark the
water level with a strip of sticky tape. Ask the students, can you tell
where the water level will be when the ice has melted? Explain, even though
part of the ice cube floats above the surface, the water level in the glass
stays the same before and after the ice has melted.
b. Ask, if anyone can tell what will happen if I place a bit if salt in the
center of an ice cube? Demonstrate by putting a pinch of salt in the middle
of an ice cube. Let the ice cube stand for ten minutes. (During the waiting
period, we will start activity c.) Examine the ice cube after the waiting
period. Ask the students what happened? The center of the ice cube melted,
while the outside of the cube remained frozen. Explain to the students that
ice does not melt until it reaches 0oC (32oF), which is the melting point of
ice. When you add salt, it lowers the melting point of ice. The ice does
not have to reach 0oC (32oF) to melt. That explains why the center of the
ice changes into water, while the outside of the cube remains frozen.
c. Another method of melting ice without heating it is to wind the ends of
wire (20cm long) around the two rocks. Support an ice cube on the mouth of
the bottle. Hang the wire weighted by the rocks over the top of the ice
cube. The students will observe the wire cutting through the ice as the
weighted wire exerts pressure on the ice. The pressure on the ice causes the
ice to melt under the wire. The water then refreezes above the wire. This
is an example of what happens when people ice skate or when people drive on
icy streets in winter.
a. The students will explain how the wire is able to cut through the ice and
refreeze on top in minutes.
b. Students will demonstrate that water is more dense than ice, which proves
why ice will float on water.
c. Students will be able to understand that ice skaters are really skating on
water. After testing the wire that cuts through the ice, students will
observe the refreezing of the ice above the wire within minutes.