Second Semester Exam Review

Front

Is digesting food a chemical or physical change?

Back

Chemical. Enzymes in the stomach break down food into simpler substances by altering their chemical compositions.

Front

Describe two physical and two chemical properties of a copper penny.

Back

Physical: Mass, volume; Chemical: Oxidizes to form green patina, reacts with strong acids

Front

Label the following changes in matter as physical or chemical.

1. Mixing salt and water.

2. Milk going sour.

3. Cooking an egg.

4. Breaking a rock with a hammer.

5. Burning coal.

Back

1. 1. Physical
2. 2. Chemical
3. 3. Chemical
4. 4. Physical
5. 5. Chemical

Front

Explain why photosynthesis is a chemical change.

Back

It uses light, water, and carbon dioxide to produce a new substance, glucose.

Front

How can you tell a chemical change has occurred?

Back

A new substance has been formed from the original reactants.

Front

Is the change when water boils and steam is produced a physical or chemical change?

Back

Physical. Water and steam are both H₂O. No new substance was created.

Front

Is baking cookies from cookie dough a chemical or physical change?

Back

Chemical. The baked cookie has its own unique properties from the cookie dough, so it is a new substance.

Front

As the logs burn and turn to ash, how does this obey the Law of Conservation of Mass?

Back

The ash and gasses formed during the reaction have equal masses to the wood prior to burning.

Front

Explain why water freezing into ice is a physical change and not a chemical change.

Back

Water in its liquid and solid forms are still H₂O, so no new substance is created.

Front

Is decomposition a chemical or physical change?

Back

Chemical. The substances are chemically broken down to create new, simpler matter with its own properties.