Question

Q1. a. At absolute zero temperature, the entropy of a pure crystalline substance is zero. Justify the statement. Why entropy becomes zero at absolute zero temperature. b. A metal rod is keeping in a moisture surrounding for long time. From your thermodynamics basics explain whether this rod is under thermodynamic equilibrium or not? Give reasons for the same. c. Explain the application of thermodynamics based on any two components of automobile.

Answer 1

Q1)

a)

• A substance's entropy decreases with temperature rise, as a substance's randomness decreases with temperature increase.
• Similarly with a drop in temperature, the orderliness of the substance is decreased and thus the entropy of the substance is decreased.
• Solid compounds have molecules routinely structured as opposed to liquid and gas. So entropy as opposed to liquid and gas is the minimum of solids.
• According to the third law of thermodynamics, the value of entropy at absolute zero temperature of a perfectly pure crystalline material is zero.
• This implies that the structure of the molecules is absolutely in order in a perfectly pure crystalline material.
• Fluid material entropies are higher than solid material entropies, and lower than gaseous substance entropies.

Hence, you can conclude that The entropy of the pure crystalline matter at absolute zero temperature is zero.

b)

Thermodynamic equilibrium:

Under thermodynamic equilibrium a system is called when there is no macroscopic movement, no flux.

But, In the give case, the metal is keeping in the moisture surrounding for long time. It will lead, the metal to get corroded. During the corrosion process, the heat transfer between metal rod and moisture should be occurred. This violates the rule of thermodynamic equlibrium concept.

Hence, you can conclude that that rod is not under thermodynamic equilibrium after long time.

c)

Thermodynamics in Automobile:

(i) Engine:

• The definition of the second thermodynamics law applied to heat engines applies equally to the internal combustion engines used in our vehicles, bikes, ships, aircraft etc.
• In internal combustion engines heat is produced inside the engine by combustion of fuel.
• The combustion of fuel is caused by spark generation as in the case of gasoline engines or by compression of the fuel as in the case of diesel engines.
• Any part of the heat produced inside the engine is used to conduct the piston inside the engine cylinder going to work.
• The piston is attached via connecting rod to the crankshaft.
• The piston's reciprocating motion is converted into the crankshaft's rotating motion, which is converted via gearbox to the rotating motion of the wheels.
• The remaining part of the heat produced within the engine is emitted as the exhaust gases or tailpipe emissions into the atmosphere.
• In this case the engine is called the source where heat is produced, while the atmosphere where heat is emitted is called the drain.
• According to the second law of thermodynamics, higher the source temperature and lower the sink temperature, higher is the engine output.
• The second thermodynamics law refers to all engine cycles, like Otto, Diesel etc., irrespective of what sort of gas they are operating on and what type of fuel.

(ii) Radiator:

• It is a heat exchanger used with traditional and/or electrified propulsion to remove the heat produced.
• Most radiators are designed to operate in the automotive, building and electronics industries.
• The radiator is also a source of heat to its surroundings, though this can be either for the purpose of heating this area, or for cooling the fluid or coolant supplied to it, as it is for cooling the engine. Despite the name, most radiators transfer the bulk of their heat instead of thermal radiation through convection.

It is the discovery of this law that has contributed to humanity's advancement through the automobiles of the present day. There is basically no other law which applies as extensively as the second thermodynamic law.