Sink or Float Science: Discovery at Home

Materials needed: 

  • Nature Journal
  • Bucket, tub or container to hold water
  • Water
  • Towel 
  • Natural items found on a walk or in your garden


  1. Before you begin, make predictions.  What do you think will float? Sink? Why?  
  2. Fill the container with water.  
  3. Place each object into the water.
  4. Note whether the object sinks or floats!
  5. Conduct your investigation, make observations and record your findings.  Perform the experiment where your scientist can easily reach into the container, and where you won’t mind a bit of water dribbling out!  Ask:  
    1. Why do you think some objects float and some objects sink?
    2. Is there anything the same about the objects that floated?
    3. What is the same about the objects that sank?

Ways to expand it:

  • Go larger. Use a larger bin to test larger objects.
  • Place an orange in your container of water. Observe what happens. Next, peel the orange and place the peeled orange into the container. Can you explain what you see?
  • Float a flat piece of foil on top of the water, then crumple the foil into a ball, and see what happens.
  • Here is a great resource to explain sink and float facts!

How do kids benefit?

  • Kids need hands-on opportunities to learn big life skills in prediction, classification and independent inquiry. This activity celebrates the scientific process. It triggers curiosity and engages kids in exploring new concepts!
  • Comparison of heavy or light, and sink or float. They can sort objects by observable properties and characteristics, such as size, shape, color, temperature (hot or cold), weight (heavy or light), and texture.
  • Basic engineering skills. Engineers solve problems with constraints. They learn to solve problems by using the engineering design process: asking questions, coming up with solutions, building, testing and improving.
  • Experimentation! When kids experiment, they're learning how to learn. Failure is an important part of experimenting, so it is valuable to let kids try things that won’t work. It’s how they figure things out!


  • Density is what decides whether an object sinks or floats in water. If something is less dense than water, it floats. If something is more dense than water, it sinks. A fluffy pillow has less density than a brick. A crayon has more density than a feather.
  • Buoyancy is how something can float in water or air. It describes the ability or tendency to float.