MATERIALS
Balloon
Paper towel
Drinking glass
Sink of water
Optional: Styrofoam peanut
PROCEDURE
1. Have child blow up a balloon. Ask, “What is inside this balloon?” (carbon dioxide gas molecules.) “Does the gas take up space?” (yes) “Why can’t you see the gas?” “Where does the gas go when the balloon pops?”
2. Now, stuff a paper towel into the bottom of a drinking glass so that it will not fall out when the glass is inverted.
3. Fill your kitchen sink full of water.
4. Ask, “Do you think this paper towel will get wet if we plunge this glass upside down into the sink of water?”
5. Hold the glass upside down and quickly plunge it into the water.
6. Count to ten while holding the glass underwater.
7. SLOWLY lift the glass up and out of the water. Be sure to hold the glass straight up and down.
8. Observe. What happened to the paper towel?
9. May also do this with a piece of Styrofoam. Place the Styrofoam in the water. Place your glass upside down over the Styrofoam and push straight down into the water. What happened?
EXPLANATION
Air (gas) molecules take up space. Therefore, water could not get into the glass. The paper towel, and the Styrofoam peanut, remained dry.
Monday, December 28, 2009
FRICTION THROUGH WATER
MATERIALS
Wide-mouthed see-through jar, or empty tennis ball can
Clay
Water
PROCEDURE
1. Add water to your container until it is almost full.
2. Take a small amount of clay and roll it into two small balls.
3. Take one of the balls and flatten it like a small pancake. Leave the other piece round and smooth.
4. Hold both pieces of clay just above the surface of the water. Ask, “Which piece of clay do you think will drop the fastest?”
5. Now drop both pieces of clay through the water at the same time. Observe. Discuss. What role did friction play with the different speeds of the clay?
EXPLANATION
Friction is the resistance of motion on the surface of a body. The more surface, the more friction, the more resistance to motion. Fish and boats are streamlined to reduce their surface so they can speed through water more easily.
Wide-mouthed see-through jar, or empty tennis ball can
Clay
Water
PROCEDURE
1. Add water to your container until it is almost full.
2. Take a small amount of clay and roll it into two small balls.
3. Take one of the balls and flatten it like a small pancake. Leave the other piece round and smooth.
4. Hold both pieces of clay just above the surface of the water. Ask, “Which piece of clay do you think will drop the fastest?”
5. Now drop both pieces of clay through the water at the same time. Observe. Discuss. What role did friction play with the different speeds of the clay?
EXPLANATION
Friction is the resistance of motion on the surface of a body. The more surface, the more friction, the more resistance to motion. Fish and boats are streamlined to reduce their surface so they can speed through water more easily.
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