Q. What is SI unit of energy?

Ans.

The SI unit of energy is called the joule. A joule is a pretty small mount of energy so often chemists will use the unit kJ =1 kilojoule = 1000 J.

Chemists sometimes use another unit to describe energy e the calorie. One calorie is equal to 4.184 J. It is the amount of energy needed to heat one gram of water by 1 degree. Technically this is not an SI unit so we shouldn't use it, but it should be familiar to you. You have probably heard of calories talked about in a food sense. In nutrition the unit of energy is the Calorie. (Notice the capital C). One Calorie is one thousand calories or one kilocalorie.