Die nötige Wärme, um 500 g Wasser zu erhitzen

In this video, we calculate the heat needed to warm water.

Question one. How much heat does five hundred grams of water need to warm from twenty degrees Celsius to eighty degrees Celsius? The specific heat capacity, c, is four point two joules per gram per degree Celsius.

You have five hundred grams of water, with a specific heat capacity of four point two joules per gram per degree Celsius.

The initial temperature is twenty degrees Celsius, and the final temperature is eighty degrees Celsius.

We need to find the heat supplied. Use heat equals mass times specific heat capacity times temperature rise, since the water stays liquid.

The temperature rise is eighty minus twenty, which equals sixty degrees Celsius.

Substitute five hundred grams, four point two joules per gram per degree Celsius, and sixty degrees Celsius.

Multiplying gives one hundred and twenty-six thousand joules. Divide by one thousand to express this as one hundred and twenty-six kilojoules.

Notice that grams and degrees Celsius cancel, leaving joules, as required for heat. Hence, the heat needed is one hundred and twenty-six kilojoules.