What is meant by the equation kJ/kg? I know that it has something to do with heat content.?

Answer 1

kJ is the abbreviation for kilojoules and kg, as you know, is kilograms so it means kilojoules per kilogram.

The Joule is the metric equivalent of the Calorie and there are 4.181 Joules to every Caolrie.

Both Joules and Caolries are measurements of Specific Heat and this is basically the amount of energy that something contains. The more energy something contains the more heat energy it is able to release.

It's probably most commonly seen in respect of the amount of energy there is in the food we eat although it's usually given in the context of kilocalories or kilojoules per 100 grams of the product.

One calorie is the amount of energy that is required to heat one gram of water by one degree centigrade. If you took one litre of water that was at 20 degrees centigrate and heated it to boiling point (ignoring any heat lost or that's used in heating the pan) then you'd need 80,000 calories (80 degree rise in temperature multiplied by 1000 grams of water). To convert to Joules multiply by 4.181 so in the case of our boiling water we'd need 334,480 Joules.

A typical person might consume 2000 kilocalories (kcal) / approx 8400 kilojoules (kJ) of food energy a day - enough to bring 25 liters of water to the boil.

Answer 2

it's a unit for specific heat. it basically means theres x amount of energy in 1 kilogram of y

specific heat of water is 4.181 kJ/kg so it takes 4.181 kJ to raise the temperature of one kilogram water one degree C

Answer 3

Kilo Joules per Kilogram, or thousands of Joules of energy per Kilogram of material.

I believe a Joule is a Newton per second but I could be wrong on that, if it is then it breaks down a Kilogram per second squared.