2.5. BIGGER THAN THE BOTH OF US
(Level: 2 : 5 :: Water Cycle)

Purpose: To observe the change in volume of water as it freezes and to introduce the concept of hibernation in amphibians.

What You Need: test tube :: waterproof marker :: beaker :: crushed ice :: salt

What You Do:

1. Fill the test tube half full with cold water and mark the water level with the marker.
2. Add crushed ice to the beaker with 1/4 teaspoon of salt sprinkled on top.
3. Insert the test tube in the middle of the beaker of ice, ensuring it remains upright.
4. As the water in the test tube cools, mark the changes in the water level. Observe closely when the water freezes and mark that level.

Questions:

1. What are the 2 changes that occur in the water as it turns to ice?
2. Why does the water level drop before it freezes?
3. The wood frog is the only North American amphibian to live north of the Arctic circle. Amazingly, they can become living ice cubes during hibernation. They produce a sugary antifreeze which prevents their cells from freezing, although the remaining body fluids freeze. A wood frog may freeze up to 50% of its intra-cellular body water because they overwinter well above the frost line. What reproductive advantage is there to hibernating above the frost line?

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