Physical And Chemical Changes

Question 1

What are physical changes?

Answer 1

Physical changes are changes in which the state of matter is changed, but not the composition of matter.

Question 2

What are chemical changes?

Answer 2

Chemical changes are when the composition of matter at the atomic level is changed.

Question 3

Are physical changes reversible? Why or why not?

Answer 3

Physical changes are not reversible, because the matter is only changing forms. If water is frozen and becomes ice, it can still be melted to become water again.

Question 4

Are chemical changes reversible? Why or why not?

Answer 4

Most chemical changes are not reversible, because some of the matter is “lost” when it changes to gas. If the gas isn’t lost, however, some chemical changes can be reversed.

Question 5

What are some indicators that a chemical change has occurred?

Answer 5

• New color
• Light
• Heat
• Bubbles of gas
• Precipitate forming
• Difficult/impossible to reverse

Question 6

When a chemical change occurs, does the amount of matter change?

Answer 6

No, there is always the same amount of matter before and after the chemical change. However, some of the matter may turn into gas.