List three signs that could indicate that a chemical reaction is taking place.  

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When a chemical reaction takes place chemical bonds are broken, atoms are rearranged and new bonds are formed. This results in a new substance that usually looks different from the reactants. Here are some indications that a new substance has formed:

1. Color change - such as iron rusting

2....

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When a chemical reaction takes place chemical bonds are broken, atoms are rearranged and new bonds are formed. This results in a new substance that usually looks different from the reactants. Here are some indications that a new substance has formed:

1. Color change - such as iron rusting

2. Temperature change - release of heat and/or light such as flames if the reaction is exothermic or cooling of surroundings if reaction is endothermic

3. Rapid release of gas bubbles

4. Formation of a precipitate which will appear as cloudiness in an initially clear solution

5. Odors that are produced during the reaction

In summary, you're looking for indications that a new substance was produced. When you mix vinegar with baking soda gas bubbles are produced that weren't present before. This is a chemical reaction. When you shake up a carbonated drink then open it you see a lot of gas bubbles, but you also know that the drink had CO2 gas dissolved in it at the start. This isn't a chemical reaction. Be sure to ask yourself if what you're observing is a new substance. 

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