# How are thermodynamic laws related to one another?

• B
• mech-eng
In summary: The zeroth law is a statement about equilibrium. The first law is a statement about conservation of energy. The second law is about what is possible with heat engines. There are reason-and-result relations in the laws of thermodynamics, but in this particular case, the zeroth law and the second law are connected because the heat flows from the higher temperature object to the lower temperature object.
mech-eng
Would you please explain how the laws of thermodynamics are related to one another? Are the laws entirely independent of one another?
I can see only a connection between the zeroth law and the second law. Following is the quote from my previous thread.

1. Zeroth law: The zeroth law of thermodynamics states that when two bodies have equality of
temperature with a third body, they in turn have equality of temperature with each other (sonntag\borgnakke)

2. First law: The First Law states that whenever energy is converted in form, its total quantity remains unchanged (www.soas.ac.uk)

3a. Second Law (Kelvin-Planck Statement): The Kelvin–Planck statement: It is impossible to construct a device that will operate in a cycle and produce no effect other than the raising of a weight and the exchange of heat with a single reservoir (sonntag\borgnakke)

3b. Second Law (Clasius Statement): It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a cooler body to a warmer body (sonntag\borgnakke)

Following is the quote from my previous thread.
256bits said:
the temperature difference is the part of the second law of thermodynamics - hotter things cool down, cooler things do not heat up - spontaneously.

So can we say that the zeroth law is the result of the second law? Is this true? Are there reason-and-result relations in laws of thermodynamics?

It is how are universe works, and for that reason they are inteconnected.
Zoroth law would be about equilibrium.
The first law is a statement about conservation of energy.
The second law is about what - possibly about the availablity of work.

vanhees71, mech-eng and topsquark
But we can make a clear statement about the connection between zeroth law and the second law as

"The heat flows from the higher temperature object to lower temperature object so two objects comes to the same temperature if they are in contact". Does this statement not join clearly the zeroth law and the second law?

Can you make clear statements that clarify the relations between "zeroth law and first law", "first law and the second law"?

Than you.

Possibly useful:
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thereq.html
There are underlying ideas about heat associated with the zeroth law of thermodynamics,
and one of those ideas was expressed by Maxwell as "All heat is of the same kind."

If A is in thermal equilibrium with B,
then every unit of internal energy that passes from A to B is balanced
by the same amount of energy passing from B to A.

This is true even if the atomic masses in A are different from those in B, and
even if the amount of energy per unit mass in A is different because the material has a different specific heat.

This implies that there is a measurable property
that can be considered to be the same for A and B,
a property upon which heat transfer depends. That property is called temperature.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/seclaw2.html
especially the catchy formulation:
If the first law of thermodynamics says you can't win,
then the Second Law of Thermodynamics says you can't even break even.

The First Law is essentially a statement of conservation of energy
and asserts that you can't get more energy out of a heat engine than you put in.

But the Second Law says that no heat engine can use all the heat produced by a fuel to do work

mech-eng said:
But we can make a clear statement about the connection between zeroth law and the second law as

"The heat flows from the higher temperature object to lower temperature object so two objects comes to the same temperature if they are in contact". Does this statement not join clearly the zeroth law and the second law?

Can you make clear statements that clarify the relations between "zeroth law and first law", "first law and the second law"?

Than you.
No,

## 1. How many laws of thermodynamics are there?

There are four laws of thermodynamics, although the fourth law is not as widely recognized as the first three.

## 2. What is the first law of thermodynamics?

The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transferred or converted from one form to another.

## 3. What is the second law of thermodynamics?

The second law of thermodynamics states that the total entropy of a closed system will always increase over time. This means that energy will naturally flow from a state of higher concentration to lower concentration.

## 4. How are the first and second laws of thermodynamics related?

The first and second laws of thermodynamics are closely related as the first law dictates that energy cannot be created or destroyed, while the second law explains how energy is transferred or converted from one form to another.

## 5. What is the third law of thermodynamics?

The third law of thermodynamics states that the entropy of a perfect crystal at absolute zero temperature is zero. This means that at absolute zero, there is no disorder or randomness in the crystal's atoms.

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