Warm Up 5/4

A teacher asks her students to classify the substances listed in the table shown as elements, compounds, or mixtures.

A student claims that all of the substances are compounds. Which statement correctly describes the student’s claim?

• A. The student’s claim is correct because a substance that contains more than two of the same atom is a compound.

• B. The student’s claim is incorrect because a substance that contains more than one element is always a mixture.

• C. The student’s claim is incorrect because the atoms in the substances are physically combined to form a mixture.

• D. The student’s claim is correct because the atoms in the substances are chemically combined to form a compound.

A student observes four actions, as described in the table.

Which actions are physical changes?

• A. P and Q

• B. Q and R

• C. R and S

• D. S and P

A researcher analyzes the water in a stream and observes that the water contains many snails, crayfish, shrimp, caddisflies, mayflies, and stoneflies. These organisms are invertebrates that are used as bioindicators for bodies of water.

What can be concluded correctly about the water in the stream?

• A. The presence of any living organisms indicates the water is safe to drink.

• B. The presence of many different types of invertebrates indicates the water is polluted.

• C. The presence of insects indicates that decomposition is taking place in the water.

• D. The presence of a variety of invertebrates indicates that the water is suitable for aquatic life.

How can upwellings improve fishing for ocean fishermen?

• They cause the ocean water to get warmer.

• They cause ocean currents to remain calm.

• They bring nutrients from the cold, deep ocean waters.

• They bring ocean currents from the equator.

Which is the best reason for scientists to study ice cores obtained from Earth’s ice caps?

• to evaluate potential oil drilling sites

• to study the quality of water stored in glaciers

• to determine the rate of melting in polar regions

• to study past climates by analyzing trapped gases and particles