Physical and Chemical Changes?

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Just need to check if my answers are right. If any of them are wrong please correct and explain why. Thanks in advance.

1. Boiling water for tea. Physical

2.Digesting food. Chemical

3. Soda goes flat. Physical

4.Shooting a rubber band. Physical

5.Grilling a hamburger. Physical

6. Adding sugar to your tea. Checmial

7. Adding lemon to your tea. Chemical

8.Mowing the grass. Physical.

9. The smell of perfume”wafts” across the room. Physical

10. Candle wax melts. Physical

11. Breaking glass. Physical

12.Making cement. Physical

13. Lighting a match. Physical

14. LED display glows in the dark. Physical

15.Firefly glows in the dark. Physical

16. Snow disappears without melting. Physical

17. Bleaching your hair. Chemical

18. Turning on a lightbulb. Physical

19. Milk goes sour. Chemical

20.Shooting off fireworks. Physical

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One Response to 'Physical and Chemical Changes?'

  1. Lindsay A - December 29th, 2008 at 12:46 pm

    Soda going flat is actually a chemical change…what is happening is that all of the carbonic acid in the soda is decomposing and producing the carbon dioxide bubble that make carbonation.

    Grilling a hamburger is a chemical change because it changes the structures of the proteins in the meat and therefore their chemical bonding

    Adding sugar to your tea is a physical change. The sugar doesn’t react with the tea, it just dissolves in the water.

    Adding lemon to your tea is physical for the same reason.

    Lighting a match is chemical. Chemicals on the match box and the match head react to start the fire.

    Firefly glowing in the dark is chemical because that light comes from a chemical reaction in the firefly’s body

    Shooting off fireworks is chemical because combustion is occurring (fire) and any time there is combustion, that is a chemical change.