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The amount of energy needed to raise the temperature of 1 gram of water by 1 °C.
It is a non-SI unit of energy equivalent to approximately 4.2 joules.
Bomb calorimetry is used to measure the calorie content of food.
However, the value produced by such experiments does not completely reflect how our body burns food.
For example, we cannot digest fiber, so obtained values have to be corrected to account for such differences between experimental (total) and actual (what we absorb) values.
A bomb calorimeter is a type of constant-volume calorimeter used to measure a particular reaction's heat of combustion.
For instance, if we were interested in determining the heat content of, say, a sushi roll, we would be looking to find out the number of calories it contains.
In order to do this, we would place the sushi roll in the bomb, seal it, and immerse the bomb in the water inside the calorimeter.
Then, we would evacuate all the air out of the bomb before pumping in pure, excess oxygengas.
After the oxygen was added, a fuse would ignite the sample, causing it to combust, thereby yielding carbon dioxide, gaseous water, and plenty of heat.
As such, bomb calorimeters are built to withstand the large pressures produced from these combustion reactions.
Once the sample is completely combusted, the heat released in the reaction transfers to the water and the calorimeter.
The temperature change of the water is measured with a thermometer.
The total heat given off in the reaction will be equal to the heat gained by the water and the calorimeter:
Keep in mind that the heat gained by the calorimeter is the sum of the heat gained by the water, as well as the calorimeter itself.
This can be expressed as follows:
Measure the oxygen consumed during combustion, Calculate the sum of the heat gained by the water, Measure the change in volume of the water after combustion, and Calculate the heat of reaction from the change in temperature of the water