This simple experiment can help children grasp the concept of density by observing real-life examples and understanding the relationship between mass, volume, and density.
Materials needed for the density experiment
A piece of cork
A piece of wood
A piece of metal (such as a small metal bolt or nut)
A container of water
Optional: a scale to measure mass
Introduce the concept of density
Explain that density is how much mass is contained in a given volume. It's a measure of how tightly matter is packed together. Higher density means more mass in a given volume, while lower density means less mass in the same volume.
Make a prediction
Ask your kids to predict which material they think will float and which will sink in water.
Testing in water: Drop the cork, wood, and metal separately into the container of water and observe what happens. Discuss the results.
The cork will likely float because it has a lower density than water. Explain that cork is less dense, so it floats on water due to the buoyant force.
The wood might also float, depending on its density. Discuss how some types of wood float (like balsa wood) due to their lower density, while denser woods might sink.
The metal will sink as it is more dense than water. Metals generally have a much higher density compared to water, causing them to sink.
If you have a scale, weigh each object to show that even though the metal piece may not be much larger in size, it is significantly heavier than the other materials, illustrating its higher density.
Discuss the results with your kids. Emphasize that density is about how tightly the particles in an object are packed together. The concept is about both mass and volume. The metal, being the most tightly packed, has the most mass in the least amount of space (highest density), while the cork, being the least dense, has less mass in the same space, causing it to float.