I. Fill in the blanks :

1.Addition of hydrogen in a substance in a reaction is known as___________ reaction.
2.In a ________ reaction two or more substances combine to form a new single substance.
3.Unbalanced reactions are also known as _________
4.Reactions in which heat is given out along with the products are called _________- reactions.
5.Reactions in which energy is absorbed are known as _________ reactions.
6.When as element displaces another element from its compound, a ________ reaction occurs.
7.Those reactions, in which two compounds react by an exchange of ions to form two new compounds, are called ________ reactions
8.Precipitation reactions produce __________ salts.
9.Reduction is the _________ of oxygen or gain of hydrogen.
10.The digestion of food in the body is an example of ____________ reaction.
11.The addition of oxygen to a substance is called __________.
12.When calcium carbonate is heated, it decomposes to give___________ and _________.