Sink or Float Science Experiment Using Balloons

The science of density is a simple concept, but there are so many things to learn in this important scientific concept. This classroom-friendly science lesson will show kids the varying density of water, oil, and dish soap suspended in cups of water. Children will have a lot of fun exploring density in this fun hands-on science project. The sink or float science experiment uses balloons, which adds an element of fun for young kids. Tie this lesson into other physical science lessons, or use it to illustrate how fish move through the water.

Getting the Sink or Float Science Experiment Ready

Setting this experiment up is super easy, and it takes very little advanced prep. You will need:

• 3 Balloons
• Dish soap
• Water
• Oil
• 3 Plastic cups
• Permanent marker
• Sink or float printable

Write the words “Water,” “Oil,” and “Soap” onto the three cups so the kids can tell which balloon goes in which cup. Fill one balloon with 1/2 a cup of water, one with 1/2 a cup of vegetable oil, and one with 1/2 a cup of dish soap. Doing this in advance will save time and reduce the mess of this project.

Be careful not to get too much air into the water balloon or the dish soap balloon or they won’t sink properly and the experiment won’t have the right results.

Doing the Sink or Float Science Experiment

Fill each cup with water. Show the balloons to the kids and tell them what each is filled with. Let them think about whether the balloons will rise or sink when placed in the water. Have them filled out their hypothesis in this printable and record their results along the way.

Drop the balloons into the water one at a time. Watch the kids react and ask them if their hypothesis was correct or incorrect and have them record that data on their sheet.

Once all the balloons are in the water, discuss density and how objects with different densities react in water. Have the kids think of other things that float in water and other things that sink in water.

The Science Behind the Sink or Float Experiment

This simple experiment ties into density. Water, dish soap, and oil all have different densities, which will determine if they sink or float. Oil is less dense than water, dish soap is more dense, and water will have the same density as the surrounding water.

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