Resources

Resources: Experiments - Why Don't Big Ships Sink?

Today, ships are made of steel and lots of heavy stuff. Some can weigh around 80, 000 tons. How can any of them possibly stay afloat? The reason is simple, and you can make your own ship float too.

All you need is:

• aluminum foil,
• a few paper clips,
• an empty aquarium (or similar large container)
• and water

Here's what you do:

1. Partially fill the aquarium or container with water.
2. Take the aluminum foil, bend it in half and make a boat. Does it float?
3. Add a few of the paper clips. Now, what happens?
4. Take another sheet of aluminum and tightly fold it in half, placing the same number of paper clips as in the first boat inside the flattened one. What happens?

Here's how it works:

The aluminum in the boat shape displaces more water than the flattened one. If the object has enough volume to displace an amount of water equal to its own weight, it will float. Its weight, or the force of gravity, will equal its buoyancy, or the force of the water pushing up on it.

Resources: Experiments - Saltwater vs. Freshwater, which is Heavier?

Does a cup of saltwater weigh more than a cup of fresh water? Let's find out!

All you need is:

• measuring cup
• Jar
• Water
• Scale
• Salt

Here's what you do:

1. Fill the measuring cup with one cup of water and use the scale to measure how much it weighs. Write it down.
2. In the jar, pour a little more than a cup of water. Stir in as much salt as the water will hold.
3. Pour one cup of the saltwater into the measuring cup and weigh it. Write it down. Does the saltwater or freshwater weigh more?

What's the result?

Though there were equal volumes of the saltwater and the freshwater (one cup each), the saltwater weighed more. This means it is heavier and thus more dense than the freshwater.

Resources: Experiments - Saltwater vs. Freshwater, which is Denser?

What do you think? Is saltwater denser than fresh water?

All you need is:

• 1/4 cup salt
• 2 cups water
• 2 clear 16 oz. glasses
• eye dropper
• food coloring
• 2 eggs

Here's what you do:

1. Fill glass with 1 cup of water.
2. Drop egg in glass. What happens?
3. Fill a second glass with 1 cup of water. Add salt and stir until dissolved.
4. Add a few drops of food coloring. Let sit for 5 minutes.
5. Add more water carefully by trickling it along the side of the glass so as not to disturb the settled colored saltwater. You may wish to use the eye dropper to add the water gently.
6. Drop egg in glass. What happens?
7. Compare how the eggs float in the two glasses. What's the difference? Why?

Here's how it works:

The reason the egg acts differently in saltwater is because of density (the weight of the liquid divided by the amount of space it occupies). The egg has a greater density than freshwater, so it sinks. When salt is added to the water, its density becomes greater than that of the egg. This means that the egg will begin to float.