The first law of thermodynamics :
According to this law, some heat given to the system is used to change the internal energy while the rest is used in doing work by the system.
This relationship is mathematically represented as follows:
ΔQ = ΔU + W
where ΔQ is the heat given or lost, ΔU is the change in internal energy and W is the work done.
The second law of thermodynamics :
If a room is not tidied or cleaned, it invariably becomes more messy and disorderly with time.
When the room is cleaned its entropy decreases but the effort to clean it has resulted in an increase in entropy outside the room that exceeds the entropy lost.
The Third law of thermodynamics :
The entropy of a pure crystalline substance (perfect order) at absolute zero temperature is zero. This statement holds true if the perfect crystal has only one state with minimum energy.