Water Tension: Pure Water Penny Lab
Lab Partners: _____________________________________________________________ Period: _____
The Molecule of Water: The water molecule is a very stable property and there are few molecules that are
more stable and difficult to decompose than H2O. In water, each hydrogen nucleus is bound to the central
oxygen atom by a pair of electrons that are shared between them. If you could see molecules of water and how
they act, you would notice that each water molecule electrically attracts its neighbors. Each has two hydrogen
atoms and one oxygen atom, H20. The extraordinary stickiness of water is due to the two hydrogen atoms,
which are arranged on one side of the molecule and are attracted to the oxygen atoms of other nearby water
molecules in a state known as "hydrogen bonding." The hydrogen bonding in water causes water tension.
To better understand and see this property of water, your lab group will hypothesize how many drops of water
can fit on the head side of a penny.
Safety Considerations: Do not consume any of the liquids in the laboratory. Be careful not to mix liquids.
It is possible that liquids may get on your hands so refrain from touching your eyes and mouth.
Question: How many drops of pure water will a penny hold?
Hypothesis: I think a penny will hold ________________ drops of pure water.
Materials:
 Penny
 Pipette
 Pure water
 Paper towel
 Beaker
Procedure:
1. Put the penny on a flat surface, heads up.
2. Use the pipette to drop water on the penny, one drop at a time.
3. Count the number of drops until the water spills over the edge of the penny.
4. Record your data.
5. Repeat steps 1 -4 for a total of 4 trials. Calculate the average number of water drops.
6. Clean and dry the table and all materials used.
Trial
Number of Drops of Pure Water Held by a Penny
Drops of Water (#)
1
2
3
4
AVERAGE:
Water Tension: Soap Water Penny Lab
Question: How many drops of soapy water will a penny hold?
Hypothesis: I think a penny will hold ________________ drops of soapy water.
Materials:
 Penny
 Pipette
 Soap water
 Paper towel
 Beaker
Procedure:
1. Repeat steps 1-5 from the Pure Water Penny Lab instructions.
2. Remember to use the SOAPY WATER!
3. Clean and dry the table and all materials used.
Number of Drops of Soapy Water Held by a Penny
Trial
Drops of Water (#)
1
2
3
4
AVERAGE:
Lab Discussion Questions:
1. What property of water allows for so many drops of water to fit on a single penny?
Term: ______________________ Definition:
2. Soap is a well-known surfactant (wetting agent that lowers the surface tension of a liquid, allowing it
easier to spread). Did the presence of surfactant have an effect on the number of drops of water that
would fit on a penny? Support your response using your data table and DETAIL!
EACH GROUP MEMBER ON A BLANK SHEET OF PAPER:


Explain the Independent Variable, Dependent Variable, 3 constants and the claim.
Rewrite your data table and create a graph for both pure water and soapy water. Make sure to include
ALL PARTS OF A GRAPH!