eLFH - Reaction Rates and Thermodynamics

Question 1

Theory of the mechanical equivalent of heat

Answer 1

Mechanical work may be transformed into heat and vice versa
The magnitude of one being always proportional to that of the other

Question 2

Two examples of the theory of the mechanical equivalent of heat

Answer 2

Muscle contraction generates heat

Explains heat generation in malignant hyperthermia

Question 3

Thermodynamics definition

Answer 3

Branch of physics governing effects of work, heat and energy on systems at macroscopic level

Question 4

Laws of thermodynamics

Answer 4

Zeroth law
First law
Second law
Third law
Combined law

Question 5

Zeroth law of thermodynamics

Answer 5

If 2 thermodynamic systems are separately in equilibrium with a third system, they must also be in equilibrium with each other

Question 6

First law of thermodynamics

Answer 6

Energy can neither be created nor destroyed

Total energy within a system remains constant, although energy may be converted from one form to another

Question 7

Example of the first law of thermodynamics with description

Answer 7

Venturi principle:

Fluid flowing through tube with a constriction in it

As constriction reached, velocity must increase

Therefore potential energy falls and is converted to kinetic energy

This results in fall in pressure of fluid at constriction

Drop in pressure can be used to entrain a second fluid

Question 8

Second law of thermodynamics

Answer 8

Entropy always tends to increase with time

Question 9

Second law of thermodynamics also known as

Answer 9

Law of increased entropy

Question 10

Entropy definition

Answer 10

A measure of chaos or disorganisation

Can be thought of as a measure of ‘unavailable energy’

Question 11

Example of the second law of thermodynamics

Answer 11

Cup falls and breaks
Some energy has been converted to sound and heat
Therefore total energy is the same but a proportion is no longer available or usable

Therefore entropy / chaos has increased

Question 12

Third law of thermodynamics

Answer 12

As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value

Question 13

Combined law of thermodynamics definition

Answer 13

Mathematical summation of the first and second laws of thermodynamics

Forms a mathematical statement / equation

Question 14

Combined law of thermodynamics equation

Answer 14

U = internal energy of the system
T = temperature in Kelvin
S = entropy
p = pressure
V = volume