How many drops of water will fit on a penny?
Jessica King
Jessica Andrews (partner)
February 2, 2009
Purpose: To find out how many water/soap drops can fit on a penny
Back round Information: Surface tension is an inward force that tends to minimize the surface area of liquid; it causes the surface to behave as if it were thing skin. If you squeeze the pipette slowly then the drops won’t come out as fast and the drops will stay on the penny longer.
Procedures
1. Get a beaker, a pipette, and a penny and some napkins.
2. Fill the beaker with water
3. Fill the pipette with water
4. Slowly squeeze the pipette on top of the penny to release the water.
5. Count the number of drops that fit on the penny.
6. Do this procedure 4 more times and record home drops the penny could hold
7. Repeat this procedure again but using soap water.
Observations
1. The easier you squeeze the pipette the slower the water comes out and you can fit more droplets on the penny.
2. The penny can hold more tap water droplets than soapy water droplets.
3. The soapy droplets slipped off easier than the tap water droplets
Results
Trial 1 / Trial 2 / Trial 3 / Trial 4 / Trial 5 / Average
Tap Water / 64 / 44 / 16 / 38 / 35 / 39.4
Soapy Water / 40 / 44 / 34 / 40 / 24 / 36.4
Calculations
To find the mean of tap water add 64+44+16+38+35 which equals 197 then divide it by 5 because there are 5 trials. The mean for tap water equals out to 39.4. To find the mean of soap water add 40+44+34+40+24 which equals 182 then divide it by 5. The mean for soapy water equals out to 36.4.
Conclusion Questions
1. Surface tension is an inward force that tends to minimize the surface area of a liquid; it causes the surface to behave as if it was a thin skin.
2. It eliminates any outliers that could affect the experiment. The more trials you take the more accurate it becomes.
3. The control group was tap water in this experiment
4. Soap water is the independent variable because the tap water is changed to soapy water during the experiment.
5. The dependent variable is how many drops will fit on the penny. This variable doesn’t change during the experiment.
6. To find out how sugar affects the surface tension do the scientific method. First put droplets onto the penny and count how many drops fits on the penny. Make observations, collect the data, develop a hypothesis, test the hypothesis, analyze the results, revise hypothesis, and make a conclusion.
Conclusion Statement
Find how many drops of tap water will fit on a penny. Then repeat the procedure and find how many drops of soap water will fit on a penny. Tap water will stay on the penny longer than the soapy water. The surface tension is stronger with tap water than soap water. The average for tap water was 39.4 in 5 trials. The average for soapy water was 36.4 for 5 trials. Surface tension for the tap water was stronger than the soapy water.