Water Olympics Lab
Pre-Lab Questions:
1. What does it mean to be a polar molecule?
2. Draw the water molecule showing its polarity.
3. List and explain the different properties of water.
Part 1: Drops on the Penny
For this part of the experiment you will need a beaker filled with water, a
dropper, and one penny. You are going to place drops of water on the
penny until the water overflows.
1. Hypothesis: How many drops of water do you think will fit on the
penny before it overflows?
Leave Space .
2. Now that you have made your hypothesis, you will begin. Each
person in the group must perform at least 3 trials. Please complete
the chart below with your results.
3. Explain the results of this section of the lab in regards to cohesion.
** Leave Space**
Part 2: Detergent on a Penny
You will be performing the same experiment as above except this time you
will be adding a little bit of detergent to the penny. A little bit of detergent
means a drop!
1. Hypothesis: How many drops of water will the penny hold?
** Leave Space**
Once you have the detergent on the penny than drop water onto the penny
until it overflows.
Please complete the chart below.
2. Did the detergent make a difference? Describe the effect of the
detergent. **Leave Space**
3. Explain how the detergent acts as a cleaning agent considering the
cohesion among molecule. **Leave Space**
Station 3:
Emulsification of Oils
Introduction: One of the most important characteristics of fats and lipids, in
general, is their insolubility in water due to their non-polar (having no
charge) nature. Lipids are made of long chains of hydrocarbons with
relatively little oxygen atoms. As a result, they tend to be non-polar and
therefore do not dissolve in polar substances such as water. (“Like
dissolves like.”) Polar substances can be dissolved in polar substances and
non-polar substances can be dissolved in non-polar substances. In human
digestion, lipids are, in part, broken down by bile, which is produced by the
liver and aids in the digestion of fats in the small intestine. Bile is not an
enzyme, but it does help the enzymes do their job. Bile helps create
minute, microscopic fat globules (a process called emulsification).
Emulsification is important because it allows lipases (important digestive
enzymes that break down fats) to attack and break down the smaller fat
globules. Larger fat globs would mean that the lipases could not access the
fats (lipids) on the interior of the lipid globs. In this activity, you will use
soap to mimic the action of bile. Soap is unique in that a soap molecule has
a polar (charged) end and a non-polar (non-charged) end. The non-polar
end grabs onto grease, oil, or fat, while the polar end grabs onto a polar
substance such as water molecules. In this way, it is able to separate lipid
molecules.
Procedure:
Read the introduction to the activity, above, and then write your research
question and scientific hypothesis.
** Leave Space**
Steps:
-Obtain TWO clean test tubes (no soap or oil). Label them.
-Fill BOTH tubes 1/3 full with water and 1/3 full with vegetable oil.
-Make a labeled drawing of your observations after doing this.
-To one tube, add about 1cm3 of soap.
-Cover the openings of BOTH test tubes with your hands/fingers and shake
vigorously.
-Draw a picture of each test tube after shaking.
-Clean your materials at the sink using soap and water and a test tube
brush. Hang the test
tubes to dry on the drying rack before moving on to the analysis questions.
Analysis Questions:
1. Which is less dense, oil or water? Justify your response.
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2. How are the test tubes different after shaking with the detergent?
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3. Explain chemically why water and vegetable oil do not mix.
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4. Detergents act as an emulsification agent. Explain what this means (you
may need to read
the introduction to this activity again) and how detergents dissolve lipids
like vegetable oil.
** Leave Space**
Station 4:
Floating Paperclips and Sinking Pepper
Procedure:
Drop a paperclip in a beaker of water. Record what happens in your class
handout.
Tear off a piece of paper towel that is slightly larger than the paperclip.
Place the piece of paper towel on top of the water.
Gently place another paperclip on the piece of paper towel. Wait a few
seconds. If necessary, gently submerge the piece of paper towel with the
tip of your finger. Record what happens to the paperclip in your class
handout. In a second beaker of water, sprinkle pepper. Record what
happens in your class handout. Using a toothpick, add a drop of liquid dish
detergent to the beaker of water. Record what happens to the pepper in
your class handout. Using the same toothpick, add a drop of liquid dish
detergent to the beaker with your paperclip. Describe what happens to the
paperclip in your class handout. Clean your materials. Rinse out the
beakers, and wipe dry with clean paper towel. Refill the beakers with fresh
water.
Analysis Questions:
1. How do you think the water is keeping the paperclip from sinking?
** Leave Space**
2. What happens if you put the paperclip on the water by a different
method?
** Leave Space**
3. Why does pepper NOT float on the surface of the water after you added
the soap?
** Leave Space**