What is heat combustion? How is choosing foods to maintain a proper diet and choosing a fuel for your house?

Question

choosing foods to maintain a proper diet
choosing a fuel to heat you home
Find the number of joules absorbed when the temperature of 20 grams of water is heated from 22 degree celcius to 31 degree celcius

Answer 1

Heat of Combustion is the energy released as heat when a compound undergoes complete combustion with Oxygen.

The first part of your question doesn't have enough information for me to answer, but I can answer the last part:

The specific heat of water is 4184 J/(kg·C).

So, if you have 20 grams of water, heated 9 degrees, the heat absorbed is:
specific heat * mass * change in temperature =
4184 J/(kg·C) * .02 kg * 9 degrees C = 753.12.