# Buoyancy Experiments for Kids

Instructor: Shelby Golden

## Bobbing for Oranges

Help younger children understand how changes in density can affect buoyancy with this experiment. All you need are the following supplies:

• An orange
• A large tub or bowl

Fill your bowl near to the top with water and then allow your students to place the orange in the water. Have them take note of what it does. Then, retrieve the orange and peel it before having them place it in the water once more. Find out if the outcome is different and have them discuss why.

The orange's ability to float is caused by air pockets in the skin. Removing the skin changes the density of the orange, therefore changing its buoyancy and causing it to sink to the bottom of the bowl. Watch these fun lessons defining density and buoyancy to introduce your students to these concepts and help them understand the experiment's outcome.

## A Sinking Feeling

Kids can complete this experiment to discover why things float or sink. Get ready for this activity with the following supplies:

• A small plastic container
• A tub or container big enough for the small container to float or sink in
• Quarters

First, your students will need to determine the volume of their small container. They can do this by filling it with water and then pouring the water into a measuring cup or beaker to determine how many milliliters, or grams, of water it holds. Then, the kids will put the empty container into the tub and add quarters until it sinks. Once the boat is on the bottom of the tub, they should measure how many grams of quarters they needed to sink the boat (one quarter = about 5.67 g). Now, students should compare the mass of the quarters to the mass of the water the container held to see if they can figure out what made the boat sink.

The kids should find that the mass of the quarters is very close to the mass of the water. This is because the amount of water held by the boat was the maximum amount of water the little container could displace without sinking. As students added quarters, they brought the craft closer and closer to the limit of water it could displace, until it finally overcame buoyancy and sank. This lesson on calculating density can be studied along with this experiment to help your middle school students learn more about the relationship between mass, volume, density and buoyancy.

## Design a Submarine

Give your students hands-on practice with the concept of buoyancy. This experiment allows kids to explore how to make something float, sink and hover. You'll need these supplies:

• Small containers with lids
• A large tub
• Several small objects of varying weight
• Rubber bands

Fill your large tub with water to begin. Your students should then work on trying to make their small container float on the top of the water. Allow them to test different options. Next, they should work to make their container sink, without simply taking off the lid and flooding it. Finally, they should work on making their container float somewhere between the top and bottom of the large tub of water. Make sure your students record their solution to each task.

This experiment helps kids understand the opposing forces involved in buoyancy. They get to see how the upward force of the water and the gravity acting on their container work against each other, while also exploring how they can affect these forces. This lesson on buoyancy, along with this lab, can help older kids work on applying the knowledge this experiment gave them.

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