Review -

1. Which of the following best distinguishes a chemical change from a physical change?

• A) A change in color

• B) A change in physical state

• C) A change in composition and formation of new substances

• D) A change in temperature only

2. During an experiment, copper turns green when exposed to moist air. This change is best classified as:

• A) Physical, because copper remains solid

• B) Physical, because only color changes

• C) Chemical, because new compounds form

• D) Chemical, because temperature changes

3. A student observes ice melting into water and concludes a new substance has formed. This conclusion is:

• A) Correct, because the state changed

• B) Incorrect, because the substance is still H₂O

• C) Correct, because density changed

• D) Incorrect, because water is not a substance

4. Which statement best supports Dalton's idea that atoms are indivisible?

• A) Atoms can be destroyed during reactions

• B) Atoms can be split using electric current

• C) Atoms retain their identity in chemical reactions

• D) Atoms are made of smaller particles

5. Which situation best illustrates the Law of Conservation of Mass?

• A) Mixing salt and water and finding a heavier solution

• B) Burning wood and seeing less solid material left

• C) Reacting hydrogen and oxygen to form water with no loss in total mass

• D) Crushing a metal and seeing it disappear

6. If two different compounds are formed by the same elements in different ratios, this supports:

• A) Law of Definite Composition

• B) Law of Conservation of Energy

• C) Law of Multiple Proportions

• D) Law of Chemical Reversibility

7. Which of the following changes can usually be reversed?

• A) Rust forming on iron

• B) Milk souring

• C) Ice melting

• D) Burning paper

8. Which of the following is an example of a chemical property?

• A) Boiling point

• B) Density

• C) Flammability

• D) Hardness

9. A liquid turns to gas upon heating. What best describes this change?

• A) Physical change; same composition

• B) Chemical change; new gas formed

• C) Chemical change; bonds broken

• D) Physical change; new particles formed

10. What is most likely happening at the particle level when water undergoes electrolysis?

• A) Particles are becoming more compact

• B) Particles remain unchanged

• C) Water molecules are broken into hydrogen and oxygen molecules

• D) Water freezes into a solid structure