Aluminum Boats

What you need:

• Aluminum foil

• Coins and washers

What you do:

• Plan a design for your boat. What shape will it be? How long, wide and deep will it be?

• Fold your aluminum foil into the shape and size of your boat.

• Once you've finished your boat, place it in a sink or tub filled with water.

• Add weight to your boat using coins or washers until it no longer floats. Count how many coins or washers your boat held.

• Make changes to your boat and then try again. See if your new boat can hold more weight than your first.

Questions to ask:

1. How many coins or washers do you think your boat will hold?

2. What happens if you place all the weight in one spot? What if you spread the weight evenly across the boat?

3. What else could you use to build a boat?

What's the science:

Did your boat sink? What about after the second try? If your boat still sinks, try spreading the same amount of weight over a greater space. When you increase the volume, or the amount of space a boat takes up, without changing its mass, it becomes less dense. 

The buoyant force, or the force of water pushing up on the boat, will be greater and allow the boat to float. The buoyant force is equal to the weight of the liquid displaced by the boat. This is why very heavy ships can stay afloat.