STEM FAIR PROJECT
Project title: Sticky Water
Mrs. Vickerman’s Third Graders - Northview Elementary
STATEMENT OF THE PROBLEM
• Does soap affect the surface tension of water?
PROJECT OVERVIEW
• Surface tension refers to water’s ability to “stick to itself “. Surface
tension can be measured and observed by dropping water (drop by
drop) on to a penny. We will observe and record how many drops of
plain water and soapy water, will hold together on the penny before
spilling off. The type of water with the greater number of drops will
have more surface tension.
RESEARCH
• Surface tension is a force on the surface of a liquid that makes it like
elastic. It is also called water skin. You can see surface tension at
work when you see a drop of water. It creates a little “bead” of
water like a dome. The water molecule is cohesive; it is very sticky.
Water molecules would rather touch water molecules than air
molecules, so they “hug” one another . This hugging pulls them
together in a ball shape. Surface tension is responsible for the shape
of liquid droplets you see on leaves and window panes. Because of
surface tension, small insects such as the water strider can walk on
water because their weight is not enough to penetrate the surface. We
saw how a paper clip could “float” on the water due to surface tension
and when we added a drop of soap the paper clip sank to the bottom.
VARIABLES
• Controlled
variables:
• 1. All groups used the same size and kind of eye droppers.
• 2. All pennies were cleaned with vinegar prior to the experiment.
• 3. All groups used the head side of the penny.
• 4. Eyedroppers were all held one inch above the surface of the penny
• Independent variable:
• The trials were done with both tap water and soapy water
• Dependent variable: Students explored whether they could put more drops
of tap water on a penny or more drops of soapy water. The type of water
that would hold together the best (have the most drops) would have the
greater surface tension.
HYPOTHESIS
• We predict that the soapy water will have less surface tension than
the plain tap water.
MATERIALS
• For each group:
• 4 droppers
• 4 small plastic cups
• 1 tray
• 1 penny
• 1 ruler
• 1 recording sheet
• Plain tap water
• Soapy water (5 ml liquid detergent/150 ml water)
PROCEDURE
• 1. Students break into 7 groups of 4 each. Each student is assigned a job: dropper,
ruler holder, counter, recorder.
• 2. The team leader cleans the penny with vinegar.
• 3. Students take turns using the eyedropper to drop plain tap water on the penny
and count how many drops it will hold until it spills over. One student holds the
ruler so that the dropper can be kept at a distance of one inch from the penny. The
recorder records the number of drops on the recording sheet. This step is
repeated four times. Each student has a turn to do each job.
• 4. Students use calculators to average the number of drops for their
group.
• 5. The groups report their findings and a class average is done.
• 6. Steps 3- 6 are repeated using soapy water.
DATA/OBSERVATIONS
Average
Number
of tap
water
drops
Average
Number
of soapy
water
drops
Red
Blue
Yellow
Green
Purple
Orange Gold
Group
15
Group
30
Group
39
Group
27
Group
13
Group
17
Group
20
10
17
12
14
16
13
8
Class
Average
23
13
CONCLUSION
• The average number of drops of soapy water on the penny was less
than the average number of drops of plain tap water. We conclude
that soapy water does affect surface tension and causes it to have
less surface tension.
WORKS CITED
• Education.com Website:
http://www.education.com/activity/article/Water_Experiment_fifth/
• Educational toy factory website:
http://www.educationaltoyfactory.com/surface_tension_experiment.h
tm
• Encyclopedia.Kids.net website:
http://encyclopedia.kids.net.au/page/su/Surface_tension
• Hann, Judith. How Science Works. London: Darling Kingsley Limited,
1991
• Wick, Walter. A Drop of Water: A Book of Science and Wonder. New
York: Scholastic Press, 1997