This blog series is made possible by a grant from the Lilly Endowment, Inc.
This fun and simple experiment about buoyancy is a great way to build knowledge. Children will have to make observations, predictions, and build fine motor skills.
Buoyancy is the ability to float in water or air. Objects that float in water have less density than objects that cannot. Dense objects tend to be heavier. People can float in water because our bodies are less dense or lighter than the water we are floating on.
Fun Fact: When we hold our breath, our bodies become less dense because we are filled with air.
Age Range: 4+
Cost: Free
What You’ll Need:
• Assortment of Household materials
• Paper
• Plastic (empty plastic bottles)
• Buttons or coins
• Plastic spoons
• Rubber bands
• Aluminum foil
• Tape
• Water (sink, tub, or a bucket)
Directions
1. Gather materials
Collect items around the house together! These items can be sauce cans, plastic containers, or any item that you might have regularly disposed of after use. Make sure to clean them before using them. If you use aluminum cans, remember that there could be sharp edges. Ask questions like “Do you think this will make a good boat?” “Will it sink? Will it float?” These questions encourage children’s judgment skills.
Set aside a container of buttons, coins, or other items to be your weight. To add an extra challenge, create different weights for each boat.
2. Fill it up
Fill a container with water. If you use a bathtub or sink, make sure the materials you choose are not so small that they might get stuck in the drain.
3. Build a boat
Work together to build a boat with your assortment of household materials. Talk through the process as you construct together. Identify the characteristics of each item. This may include the material, size, and weight. For older children, you can work together to draw the design before building.
4. Test your boat
Place your boat in the water. Revisit the questions from before: Did it float or sink? What material sank first? What fell apart? Test how many items (coins, buttons, etc.) you can put on top of your boat before it sinks.
5. Talk about it
Discuss what happened and why. Did the boat sink or float? How did each item react to the water? Did some material fall apart? Did some materials float better?
Critical Thinking Moment: Use this opportunity to talk about how different materials are made up. For example, materials like aluminum foil can float well but are very light and can not hold weight. Go through the building materials you have collected and test each one’s ability to float. This can allow a child to practice judgment to try again and build a new boat.
6. Try again
Based on all your observations, try to build a new boat. If your first boat succeeded on the first try, how can you make your boat even better? Can it hold even more weight?
If your boat did not succeed, investigate and think back on what caused the boat to not work. Once you’ve located the problem, try building it again with new ideas.
Why it Matters: This activity is a form of experimentation that allows children to learn about density and buoyancy. Through observations and predictions, your child will practice their critical thinking, reasoning, and judgment skills.
