Thermodynamic Questions

Question 1

What is the energy content/stored heat? What controls the amount of internal energy?

Answer 1

This is the energy within any substance, associated with the vibration and the motion of the molecules.
It can be thought of as heat.

Question 2

What is internal energy called in thermodynamics?

Answer 2

Enthalpy.

Question 3

What letter is given to the property of internal energy?

Answer 3

H

Question 4

How hard is it to measure internal energy of a substance?

Answer 4

It is impossible, the energy is at a microscopic level.

Question 5

When a substance changes state from a solid to a liquid to a gads, what name is given to the amount of energy that must be given to that substance in order to promote change?

Answer 5

Latent heat of fusion.

Question 6

Which of waters three states had the greatest amount of energy and why?

Answer 6

Gas/vapour. The molecules are more mobile.

Question 7

What is the definition of thermodynamics?

Answer 7

A science devoted to analysing and explaining, quantitatively, energy changes in natural processes.

Question 8

What is the relationship between internal energy and temperature?

Answer 8

An increase in temperature = an increase in enthalpy.

Question 9

Why must work be considered in thermodynamics?

Answer 9

Because heat = work.

Work must be done in energy change.

Question 10

State the first law of thermodynamics.

Answer 10

Heat = work
Energy is conserved in any transformation.
Change in energy is independent of the path taken.

Question 11

When considering a chemical reaction which way will the reaction proceed in terms of free energy?

Answer 11

Chemical reaction proceeds in a direction which leads to net reduction of free energy, energy is released in another form.

Question 12

Define thermodynamic equilibrium.

Answer 12

When two bodies have the same temperature.

Question 13

In a closed vessel, containing a single substance, liquid and gas will reach an equilibrium. Will the internal energy of the two be the same?

Answer 13

The vapour has a greater enthalpy.

Question 13

In a closed vessel, containing a single substance, liquid and gas will reach an equilibrium. Will the internal energy of the two be the same?

Answer 13

The vapour has a greater enthalpy.

Question 13

In a closed vessel, containing a single substance, liquid and gas will reach an equilibrium. Will the internal energy of the two be the same?

Answer 13

The vapour has a greater enthalpy.

Question 14

In a closed vessel, containing a single substance, liquid and gas will reach an equilibrium. Will the internal energy of the two be the same?

Answer 14

The vapour has a greater enthalpy.

Question 14

In a closed vessel, containing a single substance, liquid and gas will reach an equilibrium. Will the internal energy of the two be the same?

Answer 14

The vapour has a greater enthalpy.

Question 15

What is the thermodynamic measure if disorder called?

Answer 15

Entropy.

Question 16

What is the letter given for internal disorder?

Answer 16

S

Question 17

Why is this measure so important to the second law of thermodynamics?
Is there any point in tidying your bedroom?

Answer 17

Heat cannot pass from a hot body go a hotter one without work being put in, nature prefers disorder. No point in tidying.

Question 18

What units are used to express temperature in thermodynamics?

Answer 18

Kelvin.

Question 19

State the equation for gibbs free energy.

Answer 19

G liquid = H (enthalpy) liquid - T.S (entropy) liquid.

Vapour is same letters.

Question 20

Expression for the internal energy.

Answer 20

Enthalpy H = gibbs energy G + temp T x entropy S.

Question 21

What are the two parts of the enthalpy equation on the right?

Answer 21

G (gibbs) - the free part released in a reaction

T.S - the part bound up in the internal disorder of the system.

Question 22

What is meant by the term metastable state when referring to minerals at the earth’s surface? Give example.

Answer 22

Metastable is not the most stable but needs a push to create change. CaCO3 can exist in calcite and aragonite, both can be stable.

Question 23

When a phase boundary is drawn what does the phase boundary between the two phase represent?

Or what are the gibbs free energy values for the two different phases along the phase boundary?

Answer 23

The phase boundary is where both calcite and aragonite exist in equilibrium with each other.

Question 24

Explain why aragonite exists at the earth’s surface.

Answer 24

Because it is metastable, there is an energy barrier stopping it from converting into calcite.

Question 25

What is the typical quantity of a substance in thermodynamics?

Answer 25

A mole.

Question 26

If a reaction is studied and is found to have a delta H value that is positive, how do we describe it?

Answer 26

Endothermic - heat is gained during the reaction.

Question 27

If a reaction is studied and the delta H value is negative how do we describe it?

Answer 27

Exothermic - heat is lost during the reaction.

Question 28

We described the metamorphic mineral reaction between quartz, jadeite and albite, write the equation.

Answer 28

Jadeite + quarts = albite. And vice versa.

Question 29

What is stable at higher pressure?

Albite or jadeite+quartz

Answer 29

Jadeite and quartz

Question 30

What is meant by the clapeyron equation?

Answer 30

This equation describes the slope on the pressure vs temperature diagram.
The change of pressure divided by the change in temperature = the change in entropy divided by the change in molar volume.

Question 31

Which additional variant is needed in the clapeyron equation?

Answer 31

Molar volume.