What is entropy What is the third law of thermodynamics - Physics - Thermodynamics

Question

What is entropy ?? What is the third law of thermodynamics??

Kranav Sharma · Accepted Answer

as answered previously
ENTROPY
The entropy of a system is the measure of degree of randomness
or disorderliness in the system It is a thermodynamic property and
is denoted by the symbol S For e g a gas is more random than liquid
which in turn is more random than solid Thus entropy for solids,
liquid and gases follows the order:
Gas>liquid>solid
The particles of solid are orderly placed in their position,
thus the entropy is minimum in solids As the randomness in the
position of the particles increases from liquid to gas, the entropy
also increases Thus, solids have lowest entropy as the particles of
solid are orderly arranged and have very least random motion Gases
have highest entropy as the particles of gas are disorderly
arranged and move about very randomly
When a system undergoes a change from one state to other state,
change in entropy takes place which is denoted by symbol
Î”S We have the following relation
Î”S=q/T
where q is the heat absorbed when the process is carried out
reversibly and isothermally T is the temperature
THIRD LAW OF THERMODYNAMICS
This is the law which defines absolute zero as the condition for
an entropy of a system to be zero
The third law of thermodynamics states that at absolute zero (0
K or -273 15 oC), the entropy of a perfectly crystalline
substance is zero