To make and test predictions about sinking and floating and then classify objects according to whether they sink or float.
In this activity students will determine whether various objects sink or float in water. Whether an object sinks or float in a liquid depends mainly on two factors: density and buoyancy. However, at this level, students do not need to explain why objects sink or float. They are rather to be encouraged to observe that the same objects will sink or float every time, i.e., that there is consistency in the way the objects behave. This will help students devise their own ideas about physical properties and how they can be used to describe and categorize objects.
This lesson will also provide practice categorizing a variety of objects according to observable characteristics.
Suggested materials for activity include: wood, metal, plastic, aluminum foil, apples, oranges, plastic bottles, toy blocks, paper, bathtub toys, plastic forks, rubber balls, soda-bottle caps, pencils, erasers, and sponges.
Read aloud Who Sank the Boat? by Pamela Allen. This book (about a cow, donkey, sheep, pig, and mouse who decide to go for a boat ride) can be used as a springboard for discussing sinking and floating. See Carol Hurst's Children's Literature Site for more ideas for using this book.
If you don't have the book, you can brainstorm on what it means to sink or float. Ask students to describe things that they have seen sink or float. Elicit student ideas on what kinds of things they think will sink or float, for example: Can people float?
Then, do the Float and Sink interactive activity on the BBC Schools website. Once the page loads, you can simply follow the arrows to go through the activity. Once you get to the screen where students are asked to decide which objects float, ask students to guess which objects will float or sink. On the next screen, students should try to decide why all of the...