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B1 M2 - Physics > 2.3b Thermodynamics ( Lvl 2) > Flashcards

2.3b Thermodynamics ( Lvl 2) Flashcards

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1
Q

What is specific heat?

A

A material property that states the amount of energy that is needed to raise the temperature of 1kg of that substance by 1 degree C.

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2
Q

What is the formula for the amount of heat energy supplied?

A

Heat energy added = mass x specific heat of substance x change in temperature.

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3
Q

What is another name for heat capacity?

A

Thermal mass.

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4
Q

What is heat capacity?

A

The ratio of the amount of heat energy transferred to an object resulting in an increase in its temperature.

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5
Q

What is the formula for heat capacity?

A

Heat capacity = heat energy added / change in temperature.

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6
Q

What is heat transfer?

A

Describes the flow of heat due to temperature differences and the subsequent temperature distributions and changes.

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7
Q

What are the three methods which heat is transferred from one substance to another?

A
  1. Convection
  2. Conduction
  3. radiation.
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8
Q

What is convection?

A

This occurs in liquids and gases, where the fluid that is heated has an increase in temperature and decrease in density, therefore rising, and the cooler fluid descends to the bottom, thus being heated and continues this cycle.

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9
Q

What is conduction?

A

Where heat is directly transmitted through the material of a substance when there is a temperature difference between adjoining parts.

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10
Q

What is the only method of heat transfer in solids?

A

Conduction.

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11
Q

What is radiation?

A

Energy which comes from a source that is able to travel through space.

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12
Q

How is radiation fundamentally different to convection and conduction?

A

Substances exchanging heat need not be in contact with each other.

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13
Q

What is achieved vis the coefficient of linear thermal expansion?

A

Taking into consideration the fact that different materials expand or contract and different rates under the same temperature change.

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14
Q

What are the different types of expansion in relation of the coefficient of linear thermal expansion?

A

Linear, area and volumetric.

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15
Q

What is linear expansion?

A

When an object is heated or cooled, it’s length changes by an amount proportional to the original length and the change in temperature.

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16
Q

What is area expansion?

A

Where a 2-d solid changes is width and heigh as a result of changes in temperature.

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17
Q

What is volumetric expansion?

A

When a 3d solid experiences changes in height, width and depends with changes of temperature.

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18
Q

Why can’t the expression for the linear thermal expansion be applied to liquids or gases?

A

Because they have no fixed shape when not enclosed in a container.

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19
Q

Which expression works better for liquid and gases?

A

The coefficient of volumetric thermal expansion.

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20
Q

Why is the coefficient of volumetric thermal expansion sometimes not ideal, and what would you use instead?

A

As it can be very large so the formula will not work.

Ideal gas laws.

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21
Q

What is the 1st law of thermodynamics?

A

It describes energy conservation.

Energy can not be created not destroyed, only transformed from one form to another.

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22
Q

What is the second law of thermodynamics?

A

States that the total energy output is equal to the amount heat supplied.

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23
Q

What does the 2nd law of thermodynamics imply?

A

That there is a need for a heat source and a means of rejection or absorption of heat from the system.

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24
Q

Which term is often used instead of heat rejector?

A

Heat sink.

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25
Q

In the 2nd law of thermodynamics, what is energy transferred to the system equal to?

A

The amount of work done by the system,

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26
Q

What does entropy in a system relate to?

A

The amount of disorder within the system.

High amount of entropy = higher chaos
Lower amount on entropy = highly ordered state.

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27
Q

What is a thermodynamic cycle?

A

Where the working fluid of the system undergoes a series of process and finally returns to its initial state.

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28
Q

What are the two types of thermodynamic cycles?

A

Open and closed cycles.

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29
Q

What 5 basic elements do each thermodynamic cycle have?

A
  1. Working substance.
  2. Heat source
  3. heat receiver
  4. Pump
  5. Engine.
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30
Q

What is an open thermodynamic cycle?

A

It has an opening in the system boundary to allow a mass transfer of fluid to take place while the transient energies of heat and work are being interchanged.

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31
Q

What is a closed thermodynamic cycle?

A

A closed or fixed boundary system containing a fixed amount of vapour or gas.

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32
Q

Changes in the atmosphere effects which quantities?

A
  1. Temperature
  2. Pressure
  3. Density.
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33
Q

What happens if any of the atmospheric quantities changes?

A

A corresponding change in one of the other 2.

34
Q

What is a perfect or ideal gas?

A

One which has been shown Through experiments to adhere very closely to the gas laws.

35
Q

Which gases can be treated as perfect or ideal gases?

A

Hydrogen, oxygen, nitrogen, noble gases, and some heavier gases sucked as carbon dioxide.

36
Q

What is Boyle law?

A

The direct relationship between the pressure and volume of a gas.

37
Q

What type of process is Boyles law?

A

Isothermal process.

38
Q

How does pressure and volume of a gas relate to each other in Boyles law?

A

The pressure exerted varies inversely to the volume of the gas.

High pressure = low volume
Low pressure = high volume.

39
Q

What is Charles law?

A

The direct relationship between temperature and volume of a gas.

40
Q

What process is Charles law?

A

Isobaric process.

41
Q

How does temperature compare to volume in Charles Law?

A

Volume increases or decreases by the same factor as its temperature.

42
Q

What is Gay Lussac’s law?

A

The direct relationship between pressure and temperature of a gas.

43
Q

What process is the Gay-Lussacs law?

A

Isochoric process.

44
Q

How does pressure compare to temperature in the Gay-Lussacs law?

A

Pressure varies directly with the absolute temperature of the gas.

45
Q

What is the combined gas law?

A

Where all 3 gas laws are combined together, that takes the 3 properties (pressure, temperature and volume).

46
Q

What is the formula for the combined gas law?

A

PV/T=k

k = constant.

47
Q

How many specific heats are defined for gases?

A

2.

Constant volume
Constant pressure.

48
Q

For specific heat at a constant volume, what needs to occurs to change the thermal energy?

A

No work is done as volume remains a constant, but The heat supplied would change thermal energy.

49
Q

Which constant requires a higher specific heat to change the temperature of a gas?

A

Constant pressure.

50
Q

What is achieved in most thermodynamic processes?

A

Work.

51
Q

What occurs when the volume of gas is changed?

A

Work is done.

52
Q

In an isothermal process, what must happen to pressure or volume if you are keep temperature a constant?

A

The volume must decrease and pressure increase, or vice versa, depending on which way the temperature changes.

53
Q

What is an adiabatic process?

A

One in which no heat is transferred to or from the system.

54
Q

What does a gas that is allowed to expand freely from higher pressure to lower pressure without transfer of external energy to it?

A

It will Cool.

55
Q

What is an engine cycle?

A

Any series of thermodynamic process constituting a cycle for the conversion of heat into work.

56
Q

What are the two types of engine thermodynamic process?

A

Reversible and irreversible.

57
Q

What is a reversible process?

A

One in which the system can be restored to its initial state from the final state without causing any changes in the surroundings.

58
Q

What is required for a process to be reversible?

A

Has to be in thermodynamic equilibrium with its surroundings.

59
Q

What is a. Irreversible process?

A

One that cannot be completely reversed without causing any changes in the surroundings.

60
Q

What is another name for the irreversible process?

A

The natural process

61
Q

How does a gas turbine combustion work?

A

Using constant pressure with an increase in volume.

62
Q

How does a piston engine combustion work?

A

Constant volume with an increase in pressure.

63
Q

What is the cycle called for the piston engine?

A

Otto cycle.

64
Q

What are the four thermodynamic processes that make up a complete Otto cycle?

A

1-2 adiabatic compression.
2-3 reversible isochoric heating
3-4 adiabatic expansion
4-1 reversible isochoric rejection.

65
Q

What cycle is the gas turbine engine?

A

The Brayotn cycle.

66
Q

What are the four thermodynamic processes of the Brayton cycle?

A

1-2 adiabatic compression
2-3 isobaric heating
3-4 adiabatic expansion
4-1 isobaric cooling.

67
Q

What is refrigeration?

A

The removal and relocation of heat.

68
Q

What method of heat transfer is used extensively in refrigerators?

A

Conduction and convection.

69
Q

What are the four main components of a refrigerator?

A
  1. compressor
  2. condenser
  3. expansion valve
  4. evaporator.
70
Q

Simply, how does a refrigerator work?

A
  1. Air at low pressure enters compressor, increase temperature and pressure.
  2. gas enters condenser, heat transfer with outside air lowers temperature and becomes a liquid but remains at same pressure.
  3. Liquid flows into expansion valve, restricting flow, lowering pressure and temperature lower than surrounding air.
  4. liquid moves to evaporator where high temperature air, transfers heat with the liquid and boiling it.
71
Q

What is a heat pump, and what is the difference compared to a refrigerator?

A

It heats the air, using the same components but work in the reverse manner.

72
Q

What is latent heat?

A

Amount of heat that is absorbed or released when a body undergoes a constant temperature process.

73
Q

Why is latent heat said to be latent?

A

Because there is a change of heat but no change of temperature.

74
Q

What is the latent heat of fusion?

A

Heat added causing a change of state from solid to liquid.

75
Q

What is the latent heat of evaporation?

A

Heat added causing a change of state from liquid to gas.

76
Q

What process is solidification almost always?

A

An exothermic process.

77
Q

What is the latent heat of fusion the same as?

A

Latent heat of solidification.

78
Q

What is the latent heat of evaporation the same as?

A

Latent heat of condensation.

79
Q

What is thermal energy?

A

The kinetic energy possessed by an object or system due to the movement of particles within it.

80
Q

What is heat of combustion?

A

The energy released as heat when a substance undergoes complete combustion with oxygen.

B1 M2 - Physics (9 decks)

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