Critical Thinking
Applying Concepts Ammonia is a compound of hydrogen and nitrogen that dissolves easily in water. Can yo conclude that hydrogen and nitrogen dissolve in water? Explain your answer.
Posing Questions What information would yo need to know about a sample of air before yo could classify the sample as a solution, suspension, or colloid?
Applying Concepts Explain why yo cannot use mass or volume alone to identify substances.
Use the table to answer questions 26 and 27.
Substance |
Melting Point |
Density |
|---|---|---|
Aluminum |
660.3°C |
2.70 g/cm3 |
Table salt |
800.7°C |
2.17 g/cm3 |
Isopropyl alcohol |
−89.5°C |
0.78 g/cm3 |
Bromine |
−7.2°C |
3.10 g/cm3 |
Water |
0.0°C |
1.00 g/cm3 |
Gold |
1064.2°C |
19.3 g/cm3 |
Analyzing Data Yo have a solid with a density of 0.78 g/cm3. Is it possible that this solid is one of the substances listed in the table? Explain.
Using Tables A solid, rectangular block of material floats on water. Is it possible that the block is pure gold? Explain your answer.
Drawing Conclusions At room temperature, two white solids have the same density. With just this information, is it possible to conclude that the two solids are the same material? Explain.
Designing Experiments How could yo use density to show that a gold bracelet contains elements other than gold?
Inferring Suppose yo mix two colorless liquids together and a green solid settles to the bottom of the container. Explain why yo might be confident that a chemical change has taken place.
Concepts in Action
Comparing and Contrasting The photo shows maple sap being collected in a bucket. The sap is about 97% water and 3% sugar with traces of other compounds. Cans of 100% pure maple syrup contain about 34% water and 66% sugar. Which would have the greater viscosity—the maple sap or the maple syrup? Give a reason for your answer.
Inferring One of the general safety instructions for working in a laboratory is to tie back long hair, especially when using a lab burner. From this instruction, what can yo infer about the flammability of hair?
Applying Concepts Why might valuable documents be stored in pure nitrogen instead of in air? Recall that air is a mixture of gases, including nitrogen and oxygen.
Relating Cause and Effect Explain why painting an iron railing can slow down the rate at which the railing rusts.
Writing in Science Cheesecloth is a type of cotton cloth used by cooks. Write a paragraph explaining why a cook might wrap a lemon wedge in cheesecloth before squeezing juice from the lemon. What process for separating mixtures is the cook using?
Performance-Based Assessment
Writing in a Journal Keep a journal for a day. List five physical changes and five chemical changes that yo observe. Be sure to describe why yo think each change is physical or chemical.
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