The answers would be:
C. Bubbles appear
E. The color changes
If you'd like to know more, you can read on:
Although your selections are indications of chemical reactions, if you are referring to only the chemical reaction that occurred in your example, then the two answers are the only choices.
A chemical reaction occurs when the reactants form a new product. Signs of a chemical reaction include change is smell, color and temperature. In some cases, precipitate forms.
Answer: C: Bubbles appear E: The color changes.
Explanation:
A chemical reaction is defined as the reaction in which a change in chemical composition takes place. A new substance is formed in these reactions.
Example: Oxidation of iron to ferric oxide is a chemical change.
[tex]4Fe(s)+3O_2(g)\rightarrow Fe_2O_3(s)[/tex]
Here iron which is grey in color changes first to green and then turns brownish red.
Characteristics of a chemical reaction:
1. change in color
2. heat is gained or lost
3. evolution of gas
4. formation of precipitate
Thus when a food item that is left out of the refrigerator changes colour and evolution of gas takes place and thus would be a chemical change.
