You may have noticed that metals, for example copper, heat faster than water. You would require 4186 J of heat to raise the temperature of water by 1 degree Celsius. On the other hand 1 kg of copper would zoom to this temperature after it receives only 387 J of heat. It is known that every substance has a unique value of amount of heat required to change the temperature of 1 kg of it by 1 degree Celsius. This number is referred to as the specific heat of the substance. Let Q be the heat transferred to m kg of a substance, thereby changing its temperature by dT. The specific heat c of the substance is defined as
c = Q/mdt
Juggle the expression, and we get the heat transferred from a body to its surroundings or the other way around. This is given by.
Q = m c dT
For example the heat required to increase the temperature of half a kg of water by 3 degrees Celsius can be determined using this formula. Here m, mass of water is 0.5 kg and the dt, the temperature rise = 3 deg C and we know the specific heat of water is 4186 J/kg. So here the heat required will be
Q = 0.5 x 4186 x 3 =6280 J
It is as simple as that !!
The table below gives the specific heat of some common substances
| J/kg. o C | cal/g. o C | |
| Aluminium | 900 | 0.215 |
| Copper | 387 | 0.0924 |
| Glass | 837 | 0.200 |
| Gold | 129 | 0.0308 |
| Ice | 2090 | 0.500 |
| Iron | 448 | 0.107 |
| Silver | 234 | 0.056 |
| Steam | 2010 | 0.480 |
| Water | 4186 | 1.00 |
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