## Answer

###### Wiki User

###### 07/22/2011

**The amount of energy to boil water depends on two things: the
amount of water and the temperature of the water when you
start.**

The more water water, the more energy it takes. The colder the water, the more energy it takes.

Let say the water is at room temperature, or 20 °C. First, the water must be heated to 100 °C, which takes energy. The amount of energy is given by the specific heat of water, which is 4.186 Joule/gram °C. That means that requires 4.186 Joules of energy to heat 1 kilogram of water by 1 °C. So if you have 1 kilo grams of water at 20 °C, you have to add this much energy:

= (4.18Joule/gram °C) (100g) (100 °C - 20 °C)

= 334400 joules/°C

Of course, if you had more or less water, or it was colder or warmer, you would adjust this equation accordingly..