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Welcome to our Physics lesson on Absorption of Heat. Good and Bad Absorbers of Heat, this is the first lesson of our suite of physics lessons covering the topic of Absorption of Heat, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
Heat is a kind of energy, as explained in the first tutorial of this section "Temperature. The Zeroth Law of Thermodynamics". It is an energy of transfer, i.e. it appears only when thermal energy is transferred from one object or system into another. We can identify which of two objects in contact absorbs heat by measuring their temperature. The hottest object (the one with the highest temperature) releases heat, which is absorbed by the coldest object. This is an universal law of physics, i.e.
"Heat energy always flows from the hottest object to the coldest one."
However, the absorption of heat energy is not equal for all materials. Some materials can absorb the heat more easily (good absorbers of heat) while some other materials show resistance to heat absorption (bad absorbers of heat). As a result, if we provide the same amount of energy to each of these materials, the temperature of good absorbers increases more than that of bad absorbers for the same amount of matter.
The factors affecting the amount of heat absorbed by a substance are:
Putting all the above factors together, we obtain the formula for the specific heat capacity, c:
The SI unit of specific heat capacity is [J/(kg × K)].
Rearranging the above formula, we obtain for the heat energy absorbed by an object of mass m and specific heat capacity c when its temperature increases by ΔT:
What is the amount of heat absorbed by 300 g water at 5°C when its temperature increases to 75°C? Take the specific heat capacity of water cw = 4186 J/kgK.
We have the following clues:
m = 300 g = 0.3 kg
t1 = 5°C
t2 = 75°C
c = 4186 J/kgK
Q = ?
Applying the equation
we obtain after substitutions:
In general, dense materials such as metals, are good absorbers of heat as they contain more molecules that less dense materials and as a result, they act like reservoirs of heat energy because each molecule absorbs its own portion of energy during a heating process. Another reason why dense materials are good absorbers of heat is that their molecules can find much easier a neighbouring atom to collide with compared to less dense materials.
It is clear that vacuum is the poorest absorber of heat, as it does not contain any matter. Also, gases like air, light solids like wood, cork etc. are poor absorbers of heat.
You have reached the end of Physics lesson 13.3.1 Absorption of Heat. Good and Bad Absorbers of Heat. There are 5 lessons in this physics tutorial covering Absorption of Heat, you can access all the lessons from this tutorial below.
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