Introduction: Drops on a Penny

About: Science, Technology, Engineering, Art, and Math (or STEAM) programs at Boston Children’s Museum foster children’s curiosity, creativity, and learning as they try things out and explore the world around them.

Overview: In this activity, kids will predict how many drops of water will fit on the head of a penny before overflowing. This very simple experiment gives children an introduction to the scientific process. At the beginning, kids will make a prediction. Then they will conduct an experiment and collect data. At the end, they will compare their results with their predictions.

Skills focus:

  • Predicting
  • Experimenting
  • Observing
  • Counting
  • Collecting data
  • Comparing
  • Communicating/sharing ideas

Recommended ages: 4 and up

Estimated time: a minimum of 15 minutes

Step 1: Supplies

For this activity, you will need (per child):

  • One penny
  • Eye dropper
  • Small jar of water
  • Tray or plate to work over

Shared materials:

  • Rags or paper towels
  • Pencils and paper

Step 2: Record Predictions

Begin by asking children to make a prediction about how many drops of water they think will fit on the head of a penny. Model the idea of a "prediction" and reassure them that it is not a test, it is simply a guess based on what they think. Record everyone's predictions.

Step 3: Experiment & Data Collection

Before the experiment gets underway, you may need to demonstrate how to use an eye dropper-- this is a complicated fine motor skill for some kids.

Once kids feel comfortable with the eye dropper, they can add one drop of water at a time to the head of the penny. Have them count each drop, this is their data collection. The drops will run together and form a thick layer of water on top of the penny. Have kids make observations-- what does it look like? What will happen next?

Eventually, the water will spill off of the penny. Have everyone record the number of drops they got up to.

Step 4: Discussion

Compare people's predictions with their results. Did it take more or fewer drops than they predicted? Was anyone surprised? Did everyone get the same results? Talk about what students might have done that resulted in the wide range of results (bigger vs smaller drops, dropping from high up vs closer, etc).

Step 5: Keep Going!

Encourage kids to ask their own questions and design their own experiment to test. Here are some ideas to get you started:

  • Try it on the tail side of the penny.
  • Try it with a different coin
  • Try using a liquid other than water.
  • Experiment with different temperatures of water.
  • What happens when you add things to the water? (salt, soap, food coloring, etc)

Share you experiments with us! What worked? What didn't work so well? Leave us a comment.