Lab #1: How Can I Make a Stream of Water Bend?
Materials
Statically charged balloon
Stream of water
Directions
Blow up the balloon and tie the end. Hold the balloon by the tied end so it is free to move.
Turn the water faucet on so that a small stream of water is flowing from the faucet. Hold
the balloon close to the stream of water, but don’t let it touch the water. Do you
observe any changes?
If not, statically charge the balloon. Charge the balloon by rubbing it on your hair or on
your clothing. Start a small stream of water again, and bring the charged side of the
balloon toward the stream of water, again without touching the balloon with the water.
1. Record your observations and conclusion.
Lab #2: Soap - how does it get things clean?
Do you know how soap works? Try this experiment to find out.
What you need:
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Test tube
Glass stir rod
5 ml Cooking oil
15 ml Water
5 ml dilute dishwashing liquid
How to:
1. Put some cooking oil and water in test tube. Take your glass rod and stir
vigorously. What did you notice
2. Let the test tube stand for a few minutes. What do you notice? The oil and
water should separate into layers.
3. Add the 5 ml of dishwashing liquid to the oil and water and stir vigorously
again.
4. Observe what happens after a minute of stirring. What do you observe?
You should see a cloudy mixture. The oil and water are no longer in separate layers.
What happened?
Dishwashing liquid is a kind of soap. Normally, oil and water don't mix, so they
separate into two different layers. Soap is a surfactant, which binds to both the
oil molecules and the water molecules. The soap molecules bind to both the oil and
water molecules because soap molecules have two very different ends. One end of
soap molecules love water - they are hydrophilic. The other end of soap molecues
hate water - they are hydrophobic.
Hydrophobic ends of soap molecule all attach to the oil. Hydrophilic ends stick out
into the water. This causes a large drop of oil to break up into very small droplets
(also called small oil particles), which then disperse into the water:
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These small oil particles are then suspended in the water. This is how soap cleans
your hands - it causes larger drops of grease and dirt to be pulled off your hands,
bind to the hydrophobic ends of the soap molecules, and then suspended in water.
These small particles are then washed away when you rinse your hands.
2. Explain in your own words what you observed at each step of this
experiment. Explain how polar and non-polar molecules mix (or don’t mix) and
why. Then briefly explain, in your own words, how soap “dissolves” lipids and
disperses the oil particles in water.
Lab #3: How do Lava Lamps Work?
The secret behind the lamp’s “lava” is science. Oil is lighter, or less dense, than
water, so it rises to the surface. Salt is heavier, or more dense, than water, and
sinks to the bottom. When you add the salt, blobs of oil attach to the grains and
sink. Then the salt dissolves, and the oil returns to the top. The result? A
homemade lava lamp.
YOU WILL NEED
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250 ml or 400 ml beaker (picture below shows a clear jar with lid)
Water
Food coloring
Vegetable oil
Salt
Flashlight
STEP ONE
Fill the beaker three-quarters full of water. Add 2 drops of food coloring- choose
from red, blue, or green. A few drops go a long way!
STEP TWO
Layer the water with a small volume of oil, about 15-20 ml. Let the mixture
separate.
STEP THREE
Pour salt slowly into the beaker until you see the cool lava lamp effect. When the
bubbles stop, add more salt to see it again.
STEP FOUR
Shine a flashlight behind the jar to watch your lava lamp really glow!
3. Write your observations, in your own words, of what happens during each step of
this experiment. Then write your conclusion based on what you know about the
polarity or non-polarity of water and oil. Include an explanation of why the salt you
added dissolves in water, and not in oil (which results in the “release” of the oil
globules resulting in the lava lamp affect once the salt dissolves in the water). Hint:
re-read the first paragraph in this lab.