2.3 - Thermodynamics Flashcards

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1
Q

The thermocouple relies on the ______ effect.

A

Seebeck

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2
Q

What is the formula for converting ^C to ^F?

A
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3
Q

What is the formula for converting ^F to ^C?

A

Remember F = 9/5 C + 32 and manipulate to get result

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4
Q

How would you convert ^C to kelvin?

A

0 kelvin is -273.15 ^C

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5
Q

1 Calorie = ? J

1 BTU = ? J = Calorie

A

1 Calorie = 4186 J

1 BTU = 1055 J = 0.252 Calorie

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6
Q

What is the equation for linear expansion?

A
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7
Q

What is the interesting case about water when it is cooled between a certain temperature?

A

Between 0 and 4 ^C water actually expands when cooled.

Water therefore has its greatest density at 4C

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8
Q

Water has its greatest density at (temperature)

A

4^C

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9
Q

What is Entropy?

A

Entropy is a quantitative measure of the amount of thermal energy not available to do work

also defined as

a measure o the disorder or randomness in a closed system

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10
Q

What does the second law of thermodynamics state?

A

Total entropy of an isolated system always increases over time

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11
Q

What does the third law of thermodynamics state?

A

The third law states that the entropy of a pure crystal at absolute zero is zero

so entropy always has a positive value

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12
Q

What is meant by Adiabatic process?

A

An adiabatic process is defined as one with no heat transfer into or out of a system

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13
Q

What is an Isochoric process?

A

An isochoric process is a constant-volume process

(process fo a choir, the area for the members singing stays the same)

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14
Q

What is meant by an Isobaric process?

A

An Isobaric process is a constant-pressure process

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15
Q

What is meant by Isothermal process?

A

An Isothermal process is a constant-temperature process

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16
Q

What does Avogadros law state?

A

Avogadros law states that

'’equal volumes of all gases, at the same temperature and pressure, have the same number of molecules’’

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17
Q

What is meant by Charles law?

A

Charle’s law states that ‘‘at constant pressure, volume is directly proportional to temperature’’

P1V1 / T1 = P2V2/T2

remove pressure as P1 = P2 under charles law

V1/T1 = constant , V1 = constant x T1

(Charles puts pressure on the offense)

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18
Q

What does Gay Lussacs law state?

A

Gay Lussac’s law states that ‘‘at constant volume, pressure is proportional to temperature’’

P1V1/T1 = P2V2/T2

V1 = V2

P1/T1 = constant , P1 = constant x T1

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19
Q

What are the 2 principles of refrigeration?

A

Liquids absorb heat when changed from liguid to a gas

Gases give off heat when changed from gas to liquid

20
Q

What is meant by Heat capacity and specific heat?

A

Specific heat and heat capacity both describe an amount of energy needed to raise the temperature of a substance

21
Q

What is the equation for linear expansion?

A

Lchange = (a) (change in T)(Lo)

where a = coefficient of linear expansion

22
Q

What is a CHU?

A

1 Celsius Heat Unit

the amount of heat needed to raise the temperature of 1 lb of water 1^C

23
Q

The natural rapid and random movment of particles means that gases readily ‘spread’ or ______

(another word for mix)

A

diffuse

or diffusion

24
Q

What is meant by an absolute temperature scale?

A

a kelvin scale

(or rankine)

absolute 0 is ccolded possible

25
Q

What will the addition of impurities to water do?

A

The addition of impurities to water will decreases its melting point and increase the boiling point.

For water only

26
Q

The boiling point of water _______ with an increase in altitude (decrease in pressure)

A

decrease

64 ^C is boiling point of water on mount everest

27
Q

What is the definition of heat>

A

Heat is energy transferred between substances or systems due to a temperature difference between them.

Heat is energy in transit

Heat is a type of transfer of energy which increases the kinetic energy of the molecules within a body

28
Q

The absolute scales that has the same increments as the below scales is what?

celsius scale =

fahrenheit scale =

A

celsius scale = kelvin scale

fahrenheit scale = rankin scale

29
Q

What is meant by temperature?

A

Temperature is the degree or intensity of heat present in a substance or object

'’its hotness’’

30
Q

1 BTU = ?? J

A

1 BTU = 1054 Joules

31
Q

1 BTU = amount of heat…

A

1 BTU = amount of heat needed to raise 1 lb of water by 1^F

32
Q

1 Calorie = amount of …

A

1 Calorie = amount of heat needed to raise 1 kg of water by 1^C

33
Q

1 calorie = amount of ….

A

1 calorie = amount of heat needed to raise 1 gram of water by 1^C

34
Q

1 CHU = the amount of

A

1 Celsius heat unit (CHU) = the amount of heat needed to raise the temperature of 1 lb of water by 1^C

35
Q

If measuring very low temperatures up to -200^C what should you use?

A

A thermomteter with alcohol

Alcohol freezes at -200^C whereas Mercury freezes at -38^C

36
Q

What is the freezing point of each of these?

Alcohol

Mercury

Therefore which is better for measuring cold temps?

A

Alcohol = -200^C freezing temp

Mercury = -34^C freezing temp

Alcohol is better use

37
Q

What is the formula for specific heat capacity? (metric)

A

Q = (m)(C)(Change in T)

where Q = heat gained or lost

m = mass in kg

C = specific heat capacity in joules/kg

38
Q

What is meant by latent heat of fusion?

A

The word latent means hidden

When the phase change is from solid to liquid we must use the latent heat of fusion

39
Q

What is meant by latent heat of vaporisation?

A

Latent heat of vaporisation is the phase change from liquid to a gas

40
Q

At what temperature should a refrigerant evaporate and condense? (low or high)

A

The refrigerant must evaporate at lower temperature than the ‘cold space’ and must condense at a relatively high temperature, with a low compression level. (low condensation pressure)

41
Q

What is heat?

A

Heat is the form of energy that is transferred between systems or objects with different tempeatures

42
Q

What is meant by the term Sublimate?

A

A sublimate can go directly from a solid to a gas

43
Q

What is an isothermal process and how is it accomplished in terms of surroundings?

A

An isothermal process is a constant temperature process.

It is accomplished as in order to remain a constant temperature throughout the process, heat must be given to its surroundings as it is compressed etc

44
Q

Water is densist at what temperature?

A

4^C

45
Q

What is meant by specific heat capacity?

A

equation Q = mC(change in T)

Specific heat capacity is a materials ability to heat up, a low value means it will heat up quickly with minimal energy input

'’Low specific heat capacity means it heats up quickly with minimal energy input’’

46
Q

What is true of a substance with a high specific heat capacity?

(temperature)

A

A substance with a high specific heat capacity can absorb a large quantity of heat before it will raise in temperature