Question

circle the correct answer.

1. the law of conservation of matter states that:

a. matter can be destroyed
b. mass stays the same before and after a reaction
c. matter disappears during chemical reactions
d. mass becomes energy

1. which is a physical change?

a. burning wood
b. rusting iron
c. melting ice
d. baking cake

1. which of the following is a chemical change?

a. tearing paper
b. dissolving salt
c. freezing water
d. digesting food

1. a sign of a chemical change is:

a. change in shape
b. change in color or temperature
c. cutting into smaller pieces
d. changing state of matter

1. which energy source is renewable?

a. coal
b. natural gas
c. solar energy
d. oil

Explanation:

1. The Law of Conservation of Matter states that mass is conserved in a chemical reaction. So, mass stays the same before and after a reaction.
2. Melting ice is a physical change as it only changes the state of water from solid to liquid without forming a new substance. Burning wood, rusting iron, and baking cake are chemical changes as new substances are formed.
3. Digesting food is a chemical change as enzymes break down food into new substances. Tearing paper, dissolving salt, and freezing water are physical changes.
4. A change in color or temperature can be a sign of a chemical change. Change in shape, cutting into smaller pieces, and changing state of matter are physical changes.
5. Solar energy is a renewable energy source as it can be replenished. Coal, natural gas, and oil are non - renewable as they take millions of years to form.

Answer:

1. b. Mass stays the same before and after a reaction
2. c. Melting ice
3. d. Digesting food
4. b. Change in color or temperature
5. c. Solar energy