Chemistry surface tension penny activity

Elements Form Compounds

Unit Warm-Up Journal: Tension Activity

When atoms and ions of elements combine, there must be some force or forces holding the particles together. To get you thinking about how these forces might differ for different substances, try out this quick experiment.

Materials:

• eye dropper or straw
• shiny penny
• small glass of water
• paper towel
• second liquid (rubbing alcohol or other alcohol)
• third liquid (oil, laundry detergent or milk)

Procedure:

1. Place the penny on a paper towel on a flat surface.

2. Make an educated guess about how many water drops will fit on the penny before the water spills off the side.

3. Fill the eyedropper or straw with water. Hold the eyedropper about an inch from the penny's surface and count as you carefully add drops of water to the penny.

4. As you add drops, notice the shape that the water takes. Why might this be?

5. Stop your count when the next drop overflows the penny.

6. Dry off the penny and repeat the experiment with a second liquid.

Template

Journal: Tension Activity

1. What happens?

2. Sketch the side view of the penny just before the liquid spills over.

First liquid (water).

Second liquid.

Third liquid.

3. What could explain the differences and similarities?

4. Why did the penny need to be shiny (clean)?

5. Did the coin have to be a penny? Explain.

6. Could this property of water explain why some bugs can walk on water? Explain.

7. Could this property of water explain why a small paper clip can float on water in a glass that is so full that the water is just about ready to spill out? Explain.

8. Could this property of water explain why water "beads up" on the newly-waxed surfaces of a car but not on dirty surfaces? Explain.

9. What liquids do not behave as described in questions 6, 7 and 8 above? Explain.

10. What other observations did you find interesting?