Does Fruit Float?

This simple activity is suitable for students of all ages when investigating buoyancy and applying real-world examples.

Objectives

Students will explore the concept of buoyancy using everyday items.

Lesson Outline

Please ensure you follow your school WH&S procedures while conducting this lesson.

It is recommended Step 2 of this activity is completed outside. If completed inside, ensure rags are used to clean up spilt water.

  1. Introduce the question of “which fruit floats?” Ask why (no rights or wrongs here, just guesses!). Highlight the importance of buoyancy in real life applications, e.g. submarines (including the Deepsea Challenger which travelled to the deepest part of the ocean).
  2. Explore! Provide pairs or individuals with a bucket of water and a selection of fruit, and challenge students to determine which fruits float or sink. Students can be encouraged to record their observations for discussion later.
  3. After initial observations, ask students how they can manipulate the fruit to do the opposite to what was observed initially, and test their ideas. E.g. try peeling a banana/orange, or coring a pear.
  4. Learn from the investigations by discussing as a group which fruits float and sink. Prompt discussion by asking: Why? How did you change the fruit to do the opposite? What surprised you the most? Here you can discuss further the concepts of density, surface area, orientation, weight distribution etc., and relate to real life examples where possible.

Tools And Materials

Buckets or tubs of water (and rags to clean up spilt water)

A selection of fruit (pear, orange, banana, apple, grape, lemon, lime etc.)

Scissors/scalpels/instruments to cut or peel fruit

Further Investigations

Real world examples include fish swim bladders, free diving, ice in water, and the impacts of water temperature on buoyancy (e.g. hot water vs cold water).

Some questions you may like to ask include:

  • Why do some people float better than others?
  • Does ice always float? E.g. in water, alcohol, oil etc.
  • What’s so special about the Dead Sea?
  • Why do heavy objects such as boats float?
  • Why does melted land ice affect sea level but not melted sea ice?
  • Why do NASA astronauts train underwater?
  • How do fish swim bladders actually work?
  • Why do objects seem lighter under water?
  • What are the differences in the fruit tested?