Explain the laws of thermodynamics and why they matter.

Following are the laws of thermodynamics, with suitable example. 

1st Law of thermodynamics: 
1st law of thermodynamics deals with conservation of energy. It is stated as ' energy cannot be created or destroyed in an isolated system'. According to this law, total energy of universe remains constant. Energy just gets converted from one form to another. For example, in case of burning of cracker, chemical energy stored in cracker is converted into heat, light and sound energy.

2nd Law of thermodynamics:
2nd law of thermodynamics deals with entropy change associated with system. It is stated as ' entropy of any isolated system always increases'. According to this law, the system tries to maximize entropy. System with higher entropy is more stable than system with lower entropy. For instance, at room temperature, ice melts into water, because water has higher entropy than ice. It may be noted that entropy is measure of disorder in system. Thus, higher the disorder in system, greater is the entropy.

3rd Law of thermodynamics:
3rd law of thermodynamics also deal with entropy change in system. According to this law, entropy of a system approaches a constant value as the temperature approaches absolute zero. This means that, as the temperature decreases, randomness in system decreases and finally at 0K, system is in highly order state, hence ideally system must have zero entropy. However, there is always some residual entropy present in system even at 0K, due structural orientation of molecules.