Question

physical versus chemical changes
_____15. what is the most important question to ask to determine whether a change is physical or chemical?
a. was there a color change?
b. did the composition change?
c. was there a change in size?
d. did the change involve a change in state?
_____16. what is the name of the process by which water is broken down into hydrogen and oxygen using an electric current?
a. electrolysis
b. decomposition
c. reactivity
d. reversibility

1. during _______________, the composition of a substance does not change.

identify whether the following changes are physical changes or chemical changes. label each change either pc for physical change or cc for chemical change.
_____18. mixing vinegar and baking soda
_____19. grinding baking soda into a powder
_____20. souring milk
_____21. melting an ice cream bar
_____22. burning a wooden match
_____23. shooting off fireworks
_____24. mixing drink mix into water
_____25. bending an iron nail

Explanation:

1. A physical change doesn't alter composition, while a chemical change does. So, checking if composition changed is key.
2. Splitting water into hydrogen and oxygen by electric current is called electrolysis.
3. In physical changes, substance composition remains the same.
4. Vinegar and baking - soda react chemically to form new substances.
5. Grinding baking soda is just a change in physical form.
6. Souring milk is a chemical reaction due to bacterial action.
7. Melting ice - cream is a change of state, a physical change.
8. Burning a match is a chemical reaction with oxygen.
9. Fireworks involve chemical reactions producing light, heat, etc.
10. Mixing drink mix in water is a physical mixing process.
11. Bending an iron nail is a physical deformation.

Answer:

1. b. Did the composition change?
2. a. electrolysis
3. physical change
4. CC
5. PC
6. CC
7. PC
8. CC
9. CC
10. PC
11. PC