First Low of Thermodynamics, Formula, Preparation Method, Chemical Properties

First Low of Thermodynamics

The first law of thermodynamics states that heat is a form of energy and that thermodynamic processes are subject to the principle of conservation of energy.

This means that heat energy cannot be created or destroyed.

It is transferred from one place to another and converted into other energy.

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

First Low of Thermodynamics

First low of Thermodynamics is the heat given or lost ΔQ(Kws) in kilo watts per  second is equal to the change in internal energy ΔU(j) in joule is addition the work done W(j) in joule.Hence the First law of Thermodynamics can be written as

ΔQ(Kws)= ΔU(j)+W(j)

Where

ΔQ= is the heat given or lost

ΔU= is the change in internal energy in joule

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W= is the work done in joule

We can also represent the above equation as follows

ΔU= ΔQ-W

Hence, we can infer from the above equation that the quantity (ΔQ – W) is independent of the path taken.

Also, we can say that internal energy increases when heat is applied to the system and vice versa.

Example:1

Calculate the change in the  internal energy of the system if 4000j of heat is added to a system and a work of 1500 j is done.

Answer:

The following sign conventions are followed in the numerical

Q is positive as heat is added to the system

W is positive if work is done on the system

Hence the change in internal energy is given as

ΔU= ΔQ-W

ΔU= 4000-1500

ΔU=2500

The internal energy of the system is 2500j

Example:2

What is the change in the internal energy of the system if 6000j of heat leaves the system and  3200j of work is done on the system?

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Answer:

The change in the internal energy of the system can be identified using the formula

ΔU= Q-W

ΔU= -6000-(-3200)

ΔU= -2800joule

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