What criteria are used to distinguish between a chemical change and a physical change?

2 ANSWERS

1. jane
   

   hello
   
   There are two possible definitions for Physical and Chemical changes which I use in school:
   
   1. A physical change is reversible, a chemical change is not. For example, the freezing of water would be a physical change because it can be reversed, whereas the burning of wood is a chemical change - you can't 'unburn' it
   
   2. A physical change is a change in which no new substance is formed; a chemical change results in the formation of one or more new substances. Again, consider the previous examples: Freezing water into ice just results in water molecules which are 'stuck' together - it's still H2O. Whereas burning wood results in ash, carbon dioxide, etc, all new substances which weren't there when you started.
   
   
   hope it helps

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2. Guest643
   

    i like turtles

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