How do science concepts apply to your world? Here are some questions you'll be able to answer after you read this chapter.

• Why is a bicycle seat uncomfortable to sit on for long periods of time?
• Why do your ears pop when you drive up a mountain or fly in a plane?
• How are airplanes that weigh many tons able to fly through the air?
• Why do heavily loaded cargo ships float lower in the water than unloaded cargo ships?
• Why are airplane wings curved on the top?

What Makes Something Sink or Float?

Procedure

1. Predicting   Record your prediction of whether a wooden toothpick and a piece of clay will float in water.
2. To test your predictions, fill a bowl almost to its rim with water.
3. Place a wooden toothpick in the water. Shape a piece of clay into a cup and place it in the water. Record your observations.
4. Remove the clay from the water, dry it with a paper towel, and then tightly roll it into a small ball. Place the ball of clay in the water and record your observations.

Think About It

1. Evaluating   Which of your predictions were correct?
2. Observing   What effect did rolling the clay into a ball have on its ability to float?
3. Formulating Hypotheses   What property of the clay did you change by rolling it into a small ball? Explain how this change affected the clay's ability to float.