Cave Icicles

Hypotheses:

I Predict that stalagmites and stalactites are formed by water dripping from the ceiling and freezing on the floor.

Materials:

1. sheet of black poster board

2. tape

3. scissors

4. four drinking glasses, same size

5. yarn

6. cellophane tape

7. four washers

8. ruler

9. small saucepan

10. pot holder

11. tablespoon

12. water

13. potassium nitrate

Procedure:

Part one: constructing the cave

1.Cut a nine-inch piece from the black poster board, and bend the piece into a semicircle.

2. Place the four drinking glasses around the outside of the semicircle. Tape the ends of the semicircle to the outside glasses. Check to make sure that the tops of the drinking glasses are at least one-inch above the top edge of the poster board. If not, you will need to either trim the poster board or find taller glasses.

3. Cut the black yarn into two 16-inch pieces. Tie washers to the ends of each piece of yarn.

4. Stretch the yarn pieces across the glasses so that the pieces crisscross and sag slightly.

Part two: Mixing the mineral solution

1/ Fill the small saucepan with water, and add salt, stirring with the tablespoon until no more potassium nitrate dissolves.

2/ Heat the water and continue stirring. You will find that you can add even more potassium nitrate.

3. Fill each glass with the warm solution.

4. Allow your cave to sit for about a week, and observe any changes.

Conclusion:

I conclude that stalactites and stalagmites are formed by large amounts of salt vapor forming on the cave walls.

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