Which is an example of a chemical reaction?

  1. Paper cut into small pieces 
  2. Chocolate melting in a pan 
  3. Flour and sugar mixed in a bowl 
  4. Cookies baking in an oven 


The processes, in which a substance or substances undergo a chemical change to produce a new substance or substances, with entirely new properties are known as chemical reactions. 

The correct answer is: Cookies baking in an oven 

    Cookies baking in an oven is a chemical reaction.
    • When the materials are heated they undergo a chemical change.
    • The reaction is non reversible.
    • The sugar, flour, and eggs can no longer be separated. The properties of the materials have changed so it is a chemical change.