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 titanium metal welded in an argon atmosphere?
• What causes a crystal of rock salt to shatter when it is struck?
• Why is water a liquid while carbon dioxide is a gas at room temperature?
• What advantage does jewelry made from a gold-silver alloy have over jewelry made from pure gold?
• How does mixing other elements with silicon make silicon a better conductor of electric current?

What Can the Shape of a Material Tell You About the Material?

Procedure

1. Use a wood splint or small lab spatula to place a small sample of table salt on a sheet of black construction paper.
2. Use a hand lens to examine the sample. On a separate sheet of paper, sketch the shapes of some pieces in the sample.
3. Repeat Steps 1 and 2 with each of the compounds your teacher provides.

Think About It

1. Observing   Compare the shapes of the pieces in the different compounds.
2. Predicting   Could any differences you observed be used to identify a compound? Explain your answer.
3. Formulating Hypotheses   What could be happening at the atomic level in compounds to produce the different shapes you observed?