Grade 11 University Chemistry - Drops on a Penny - PEOE
Introduction
Hydrogen bonds and surface tension give water some amazing properties. In this activity, we will see
how many drops of freshwater vs. alcohol we can fit on a penny, and we will use the properties of
water we have learned to try and explain what we see.
Instructions
Materials:
1. Plastic cups
2. Pennies
3. Tap water
4. Disposable pipettes
5. Rubbing alcohol
6. Paper towels
Procedure:
Assemble the materials your group will need. Your group will need 2 plastic cups: one containing tap
water and one containing rubbing alcohol. Also obtain one penny, two paper towels, and one
disposable pipette for each person in the group.
Fill out the Predict and Explain boxes on the PEOE sheet. How many drops of water do you think can fit
on the head of a penny? How about alcohol? Why do you think so? Are your predictions for water vs.
alcohol the same or different? Why or why not?
Each member of the group should do the following steps:
1. Take one of the pennies and place it head side up on a paper towel on the lab table.
2. Slowly and gently, use the pipette to place drops of water on the penny until one drop makes
the water overflow the edges of the penny. Be sure to count the number of drops as you add
them.
3. Record the number of drops you added minus the one that made the water overflow in the
Observe box on the PEOE sheet. Make sure you write out any other qualitative observations as
well.
4. Dry the penny thoroughly with the other paper towel and squeeze all the water out of the
pipette.
5. Repeat steps 2, 3, and 4, using rubbing alcohol instead of water. It is important to use the
alcohol second.
6. Discuss your results and observations with your group members and then fill out the second
Explain box on the PEOE sheet.
FOCUS QUESTION: What do you think will happen when you put droplets of freshwater onto a coin
vs. when you put droplets of alcohol onto a coin?
PREDICT (Enter your hypothesis here)
EXPLAIN (Why do you think this will
happen?)
OBSERVE (Enter the observations you make
during the lab here)
EXPLAIN (Why do you think things
happened the way they did?)
SO WHAT? Answer the following questions.
List two (2) real world examples in which the following properties of water can be seen:
cohesion, adhesion, surface tension. Use online resources or your textbook!
Why/how are these properties of water important for life?