Take a Guess: How many drops of water can fit on one side of a penny? _____

Part A: Perform a CONTROL test for comparison with later results.
Step 1: Rinse a penny in tap water and dry completely.
Step 2: Place the penny on paper towel.
Step 3: Use an eye dropper to place drops of WATER on the penny (one at a time) until ANY amount of water runs over the edge of the penny.
Step 4: Record the number of drops for that trial in the table.

Repeat steps 1 - 4 three more times (for the other trials) before calculating your average.

 Part B: Perform tests with the TESTING LIQUID.
Step 1: Start with a “clean” penny. Rinse the penny in tap water and dry completely. Be sure to remove as much residue as possible - without using soap!
Step 2: Hold the penny with the tweezers provided, then dip it into the TESTING LIQUID. Allow extra liquid to drip off the penny into the container before the next step.
Step 3: Place penny on paper towel. Place drops of WATER on the penny (one at a time) until ANY amount of water runs over the edge of the penny.
Step 4: Record your observations and the number of drops for that trial in the table.

Repeat steps 1 - 4 three more times before calculating the average.

 Part C: Answer each question related to the experiment.

1. Explain your results in terms of cohesion and surface tension.

2. Compare your results with other groups. Did they have the same results? Why or why not? Give at least two reasons.

T. Trimpe, 1999