Lecture 2 Thermodynamics

Question 1

What is a system?

Answer 1

Region of the universe under study

Question 2

What are surroundings?

Answer 2

Regions outside the boundaries of the system

Question 3

A system is separated from the remainder of the universe by…

Answer 3

A boundary which may or may not be imaginary which delimits( determines the limits or boundaries of )a finite volume and through which heat or other forms of energy may pass.

Question 4

There are ……dominant classes of systems

Answer 4

There are three dominant classes of systems

Question 5

What is an isolated system?

Answer 5

A system where there is no exchange of either matter or energy in between the system and the surroundings

Question 6

What is a closed system?

Answer 6

A system where exchange of energy in between the system and surroundings is possible but matter can neither enter into nor leave the system

Question 7

What is an open system?

Answer 7

A system where matter as well as energy can cross the boundary and thus there can be exchange of these with its surroundings.

Question 8

When is a system said to be homogenous?

Answer 8

A system is said to be homogenous when it has the same chemical composition throughout.

Question 9

Example of homogenous system

Answer 9

Mixture of gases

Question 10

What is a heterogenous system?

Answer 10

A system consisting of two or more different phases which are homogenous in themselves and are separated from one another by definite bounding surfaces.

Question 11

Example of heterogenous system

Answer 11

Ice in contact with water

Question 12

A system is said to be in a particular state when…

Answer 12

When specific values of the properties of the system are known.

Question 13

What are these properties of the system called?

Answer 13

Variables of state

Question 14

How many variables of state are they?

Answer 14

Four

Question 15

What are the variables of state?

Answer 15

Temperature, Pressure, Volume, Composition

Question 16

If the values of these four variables of a system are known…

Answer 16

All other properties such as mass, viscosity, density etc are thereby definitely fixed.

Question 17

What is thermodynamic state?

Answer 17

It may be thought of as the instantaneous quantitative description of a system with a set number of variables held constant.

Question 18

The variables of the system can be classified into:

Answer 18

Intensive and extensive variables

Question 19

What is an intensive variable?

Answer 19

It is a physical quantity whose value does not depend on the amount of the substance but depends on the nature of the substance.

Question 20

Examples of intensive variables

Answer 20

Temperature, Pressure, density, viscosity

Question 21

What is an extensive variable?

Answer 21

It is a physical quantity whose value is proportional to the size (quantity of matter) of the system it describes.

Question 22

Extensive variable can be expressed as…

Answer 22

Can be expressed as the sum of the quantities for the separate subsystems that compose the entire system

Question 23

………one type of extensive quantity by a ………. type of ……… quantity will in general give an ………. quantity.

Answer 23

Dividing one type of extensive quantity by a different. type of extensive quantity will in general give an intensive quantity.

Question 24

Changes in a system are often characterised by…

Answer 24

Changes in a system are often are often characterised by differentials of its state variables.

Question 25

A differential describes…

Answer 25

A very small change of a dependent variable (dy).

Question 26

If in a function y=f(x), a small change in the variable (dx) occurs. It can be calculated from…

Answer 26

The product of the first derivative of the function f(x) multiplied by dx: dy=f’(x)dx.

Question 27

Most thermodynamic equations are functions with several variables hence the derivatives can be obtained with

Answer 27

Respect to one variable if the others are kept constant

Question 28

What is partial differentiation?

Answer 28

Derivatives being obtained with respect to one variable if the others are kept constant

Question 29

dG is ……… , G is …….. , G depends only on …..

Answer 29

dG is a total differential , G is a state function , G depends only on the state of the system, not on the way in which that state was achieved.

Question 30

The central concept of thermodynamics is that of

Answer 30

energy, the ability to do work

Question 31

Energy can be transferred into a body by

Answer 31

Heating, compression or addition of matter

Question 32

Energy can be extracted from a body by

Answer 32

Cooling, expansion or extraction of matter

Question 33

In mechanics, energy transfer results from

Answer 33

A force which causes displacement

Question 34

The product of the force and displacement is?

Answer 34

The amount of energy transferred

Question 35

Thermodynamic systems can be thought of as….

Answer 35

Transferring energy as the result of a generalised force causing a generalised displacement with the product of the two being the amount of energy transferred.

Question 36

These thermodynamic force-displacement pairs are known as?

Answer 36

Conjugate variables

Question 37

Examples of Conjugate variables

Answer 37

Pressure- volume , temperature-entropy and chemical potential-particle number.

Question 38

In thermodynamic equilibrium, what happens in isolated systems as time goes by?

Answer 38

Internal differences in the system tend to even out. P and T tend to equalise as do density differences.

Question 39

What is thermodynamic equilibrium?

Answer 39

It is a state that a system in which all equalising processes have gone to completion is considered to be in.

Question 40

How many types of thermodynamic equilibrium are there, what are their names and define them.

Answer 40

There are three thermodynamic equilibrium types. They are:
Thermal equilibrium
Chemical equilibrium
Mechanical equilibrium

Thermal equilibrium- Its temperature should not change with time

Chemical equilibrium- Its chemical composition should not change with time

Mechanical equilibrium - There should not be any movement of particles of the constituents of the system in itself and in between itself and surroundings,

Question 41

What is a thermodynamic process?

Answer 41

It may be defined as the energetic evolution of a thermodynamic system proceeding from an initial state to a final state.

Question 42

Tell the number, name and definition of the types of thermodynamic processes.

Answer 42

There are six

An isobaric process occurs at constant pressure (P)

An isochoric process occurs at constant volume (V)

An isothermal process occurs at constant temperature (T)

An isentropic process occurs at constant entropy (S)

An isenthalpic process occurs at constant enthalpy (H)

An adiabatic process occurs without loss or gain of heat (Q).

Question 43

Often when analysing a thermodynamic process it can be assumed that…

Answer 43

Each intermediate state in the process is at equilibrium. This will considerably simplify the situation.

Question 44

Thermodynamic processes which develop so slowly as to allow each intermediate step to be an equilibrium state are said to be…

Answer 44

Reversible processes.

Question 45

Thermodynamic considerations of biological processes require?

Answer 45

Require an extension of the classical thermodynamics of equilibrium towards the direction of thermodynamics of irreversible processes.

Question 46

This extension was taken in how many steps and what are they?

Answer 46

Taken in 2 steps.

1. Only small deviations away from equilibrium are taken into consideration. In this case, linear relationships between forces and fluxes can be assumed.
2. In contrast to these linear approaches, the thermodynamics of non-linear processes can calculate systems far from equilibrium, where steep gradients of potential exist. In this case, the so- called dissipative structures appear which are stationary states with completely new qualities.

Question 47

What is thermodynamics?

Answer 47

Branch of physics that deals with the change in the pressure, temperature, volume on microscopic systems using statistics. The energy is transferred. The result is in movement.