4th Grade

What makes an object sink or float in water? Here are two 4th grade science projects that will help us to find out. It can’t be how heavy it is – aircraft carriers are extremely heavy, and they float just fine.

It can’t be what it’s made of either, since boats can be made of wood, metal, fiberglass, plastic – lots of different materials. So what is it?


Project #1:
Shape of Floating Objects

In these science projects for 4th graders, we’ll try three different shapes and see which ones float in water.


    • Large bowl or aquarium
    • Aluminum foil
    • Large marble or bouncy ball


1. Fill the bowl or aquarium with water.

2. Cut out four squares of aluminum foil, roughly 8-12 inches on a side. Make sure they are all the same size.

3. Fold the first square in half, then in half again. Raise the edges slightly to make a raft shape.

4. Crumple the second square into as tight a ball as you can.

5. Twist the third square into a tight tubular shape

6. With the fourth square, fold it in half twice just as you did to the first square. Then wrap it around the marble or bouncy ball so that it takes on a spherical shape. Unfold it just enough to take the ball out, then try to shape it into a hollow ball again.

7. Come up with your hypothesis – which of the four shapes will float, and which will sink?

8. Drop the shapes into the water one by one and observe what happens? Did the ones that sank sink in the same way, or different ways? Record your observations.

*TIP: These 4th grade science projects are infinitely expandable – you can try out any shape you want, as long as the weight of your original aluminum foil squares is the same.

Project #2:
Maritime Engineering

Now that we know what kind of shapes float and which do not, let’s explore which shapes float better than others. In this 4th-grade science fair project, ideal for the creative student, we’ll test several designs of boats to see which one can hold the most weight


    • Aluminum foil
    • Large bowl or aquarium
    • 50+ paper clips



1. Start by researching different kinds of boats. Find images of them in a book or online. Pay close attention to the part of the boat called the hull, since this is the part you are trying to replicate.

2. Here are a few types of boats you may want to start with: dugout canoe, catamaran, destroyer, galleon, rowboat (dinghy)

3. Cut out aluminum squares as in Experiment 1. Shape them as well as you can into the hull shapes that you researched. You can make any kind of hull you want, as long as the total amount of aluminum foil used is the same for all boats

4. Come up with your hypothesis – which of these boats will hold the most weight? The least?

5. Place all of your boats into the bowl or aquarium. Drop a paperclip into each one. Continue going around adding one paper clip at a time. Whenever a boat sinks, record the number of paper clips it was holding, then add one. This is how many paper clips the boat can hold

6. Present your results in a chart – was your hypothesis confirmed?

*TIP: These 4th grade science projects can be made more festive by using the paper clips in interesting ways. Use them to fashion masts for your ships, or make bowsprits or mastheads. Be creative with the paperclips, but make sure that you still count the decorative paper clips in the same way you count the ones that are “dead weight.”

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