Water Lab: Hang on Mr. Lincoln!

Introduction: Surface tension refers to water’s ability to “stick to itself.” Surface tension can be measured and observed by dropping water (drop by drop) onto a penny. The number of water drops that can fit on a penny will surprise you!

1.  Initial Observation: Observe surface tension by seeing how many drops of water can fit onto a penny.

  1. Use the pipette to carefully place water drop-by-drop on the coin (Lincoln side up).
  2. Try to make sure the drop size is consistent.

Number of Drops: ______

2.  Problem: How does soap affect water’s surface tension?

  1. Hypothesis: Write a statement predicting what effect you think adding soap to water has on its surface tension.

3.  Test your hypothesis: Compare the number of drops of tap water that can fit on a penny with the number of drops of soapy tap water that can fit on a penny. You need to complete 5 trials with each liquid. Record the number of drops for each trial in the data table below.

  1. Use a pipette to carefully place water drop-by-drop on the coin.
  2. Try to make sure each droplet is the same size.
  3. Dry the penny carefully after each trial.
  4. Use the designated pipette for each container (do NOT mix them up!!!).

4.  Data Table:

Trial 1 / Trial 2 / Trial 3 / Trial 4 / Trial 5 / Average
Tap Water
Soapy Water

5.  Analysis & Conclusion: Write a short paragraph below that explains how soap affects the surface tension of water. Use your data to support your answer. As part of your conclusion, you should also make a statement about possible error in your experiment.

6.  Post-Lab Follow-Up Questions: Answer these questions thoughtfully.

  1. Explain the concept of surface tension.
  1. Why were many trials taken and averaged before making a conclusion?
  1. In this experiment, what was your control group?
  1. In this experiment, what was your dependent variable?
  1. In this experiment, what was the independent variable?
  1. Complete a neat, accurate graph of your data. This time, a BAR graph is appropriate.


Title: ______