The unit of measurement for energy is the joule (J). It takes 4.2 joules of energy to heat up 1g of water by 1 degrees celsius. This amount of energy is called a calorie (cal), i.e. 1 calorie = 4.2 joules.
Information about the energy provided by food products is given in kilocalories (kcal). When any chemical change takes place it is accompanied by an energy change, i.e. energy can be taken in or given out. The relative amounts of energy produced by food or fuels can be measured using calorimetry.
To measure the temperature change that takes place when a fuel burn0,s follow this method:
1. Place 100g of water in a calorimeter (a container made of glass or metal) and measure the temperature change of the water.
2. Find the mass (in grams) of the fuel to be burned.
3. Burn the fuel under the in the calorimeter for a few minutes.
4. Record the new temperature of the water and calculate the temperature change of the water.
5. Weigh the fuel and calculate how much fuel has been used.
6. Calculate the energy released (Q) with the following formula: Q = m x c x temperature change
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