Thermodynamic Questions Flashcards
What is the energy content/stored heat? What controls the amount of internal energy?
This is the energy within any substance, associated with the vibration and the motion of the molecules.
It can be thought of as heat.
What is internal energy called in thermodynamics?
Enthalpy.
What letter is given to the property of internal energy?
H
How hard is it to measure internal energy of a substance?
It is impossible, the energy is at a microscopic level.
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?
Latent heat of fusion.
Which of waters three states had the greatest amount of energy and why?
Gas/vapour. The molecules are more mobile.
What is the definition of thermodynamics?
A science devoted to analysing and explaining, quantitatively, energy changes in natural processes.
What is the relationship between internal energy and temperature?
An increase in temperature = an increase in enthalpy.
Why must work be considered in thermodynamics?
Because heat = work.
Work must be done in energy change.
State the first law of thermodynamics.
Heat = work
Energy is conserved in any transformation.
Change in energy is independent of the path taken.
When considering a chemical reaction which way will the reaction proceed in terms of free energy?
Chemical reaction proceeds in a direction which leads to net reduction of free energy, energy is released in another form.
Define thermodynamic equilibrium.
When two bodies have the same temperature.
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?
The vapour has a greater enthalpy.
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?
The vapour has a greater enthalpy.
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?
The vapour has a greater enthalpy.
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?
The vapour has a greater enthalpy.
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?
The vapour has a greater enthalpy.
What is the thermodynamic measure if disorder called?
Entropy.
What is the letter given for internal disorder?
S
Why is this measure so important to the second law of thermodynamics?
Is there any point in tidying your bedroom?
Heat cannot pass from a hot body go a hotter one without work being put in, nature prefers disorder. No point in tidying.
What units are used to express temperature in thermodynamics?
Kelvin.
State the equation for gibbs free energy.
G liquid = H (enthalpy) liquid - T.S (entropy) liquid.
Vapour is same letters.
Expression for the internal energy.
Enthalpy H = gibbs energy G + temp T x entropy S.
What are the two parts of the enthalpy equation on the right?
G (gibbs) - the free part released in a reaction
T.S - the part bound up in the internal disorder of the system.
What is meant by the term metastable state when referring to minerals at the earth’s surface? Give example.
Metastable is not the most stable but needs a push to create change. CaCO3 can exist in calcite and aragonite, both can be stable.
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?
The phase boundary is where both calcite and aragonite exist in equilibrium with each other.
Explain why aragonite exists at the earth’s surface.
Because it is metastable, there is an energy barrier stopping it from converting into calcite.
What is the typical quantity of a substance in thermodynamics?
A mole.
If a reaction is studied and is found to have a delta H value that is positive, how do we describe it?
Endothermic - heat is gained during the reaction.
If a reaction is studied and the delta H value is negative how do we describe it?
Exothermic - heat is lost during the reaction.
We described the metamorphic mineral reaction between quartz, jadeite and albite, write the equation.
Jadeite + quarts = albite. And vice versa.
What is stable at higher pressure?
Albite or jadeite+quartz
Jadeite and quartz
What is meant by the clapeyron equation?
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.
Which additional variant is needed in the clapeyron equation?
Molar volume.
