= temperature variation
Specific heat capacity
It represents the relationship between heat and temperature. The formula on the left decribes this relationship exactly.
The difference between heat and temperature is often misunderstood. If heat is gained, the temperature increases. If heat is lost, the temperature decreases.
Heat is a form of energy. Electrical, chemical, kinetic and also other forms of energy can be converted into heat.
Temperature is a measure of how hot something is. It is assumed that water solidifies at 0° C and boils at 100° C.
Hence, heat is measured in joules (J), which is the SI unit for energy (in the context of food and diet, the energy unit of choice is calories; 1 calorie = 4.18 J).
-If we have 2 cups of coffee, and we add them together, what happens to the temperature and to the energy of the final double cup of coffee? The final temperature will be the same of each separate cup. The energy content of the double coffee, however, will be twice as much as in each separated cup.
The main questions you will be asked in this topic are, for example:
How much heat must be given to a liter of water for its temperature to be raised from 0° C to 100 ° C? or from 10° C to 20° C?
What if I want to raise the temperature of a piece of metal form 0° C to 100 ° C? Is the amount required the same as for the water?
The answer is no! Each material has a particular relation between heat and temperature: this is its specific heat capacity .
Examples:
The specific heat capacity of water : 4186 J / Kg K
That means that 4186 J are required to increase the temperature of 1 kg of water by 1 degree.
It is a lot of energy, if compared to the energy required to raise the temperature of metals, as shown below.
That is why we have to wait quite a while for the water to boil... And that is also why water is so often used as a vehicle to carry heat. For instance, in powerstations, home heating systems, car engines cooling system, etc...
The specific heat capacity of copper: 386 J / kg K
and of lead: 128 J / kg K
As you can infer from the numbers above, metals get hot more easily than water.
-As you can see, the units for specific heat capacity are given in K (degrees kelvin). That means that all calculations regarding heat must be carried out using kelvin .
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