2.3 - Thermodynamics Flashcards
The thermocouple relies on the ______ effect.
Seebeck
What is the formula for converting ^C to ^F?
What is the formula for converting ^F to ^C?
Remember F = 9/5 C + 32 and manipulate to get result
How would you convert ^C to kelvin?
0 kelvin is -273.15 ^C
1 Calorie = ? J
1 BTU = ? J = Calorie
1 Calorie = 4186 J
1 BTU = 1055 J = 0.252 Calorie
What is the equation for linear expansion?
What is the interesting case about water when it is cooled between a certain temperature?
Between 0 and 4 ^C water actually expands when cooled.
Water therefore has its greatest density at 4C
Water has its greatest density at (temperature)
4^C
What is Entropy?
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
What does the second law of thermodynamics state?
Total entropy of an isolated system always increases over time
What does the third law of thermodynamics state?
The third law states that the entropy of a pure crystal at absolute zero is zero
so entropy always has a positive value
What is meant by Adiabatic process?
An adiabatic process is defined as one with no heat transfer into or out of a system
What is an Isochoric process?
An isochoric process is a constant-volume process
(process fo a choir, the area for the members singing stays the same)
What is meant by an Isobaric process?
An Isobaric process is a constant-pressure process
What is meant by Isothermal process?
An Isothermal process is a constant-temperature process
What does Avogadros law state?
Avogadros law states that
'’equal volumes of all gases, at the same temperature and pressure, have the same number of molecules’’
What is meant by Charles law?
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)
What does Gay Lussacs law state?
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
What are the 2 principles of refrigeration?
Liquids absorb heat when changed from liguid to a gas
Gases give off heat when changed from gas to liquid
What is meant by Heat capacity and specific heat?
Specific heat and heat capacity both describe an amount of energy needed to raise the temperature of a substance
What is the equation for linear expansion?
Lchange = (a) (change in T)(Lo)
where a = coefficient of linear expansion
What is a CHU?
1 Celsius Heat Unit
the amount of heat needed to raise the temperature of 1 lb of water 1^C
The natural rapid and random movment of particles means that gases readily ‘spread’ or ______
(another word for mix)
diffuse
or diffusion
What is meant by an absolute temperature scale?
a kelvin scale
(or rankine)
absolute 0 is ccolded possible
What will the addition of impurities to water do?
The addition of impurities to water will decreases its melting point and increase the boiling point.
For water only
The boiling point of water _______ with an increase in altitude (decrease in pressure)
decrease
64 ^C is boiling point of water on mount everest
What is the definition of heat>
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
The absolute scales that has the same increments as the below scales is what?
celsius scale =
fahrenheit scale =
celsius scale = kelvin scale
fahrenheit scale = rankin scale
What is meant by temperature?
Temperature is the degree or intensity of heat present in a substance or object
'’its hotness’’
1 BTU = ?? J
1 BTU = 1054 Joules
1 BTU = amount of heat…
1 BTU = amount of heat needed to raise 1 lb of water by 1^F
1 Calorie = amount of …
1 Calorie = amount of heat needed to raise 1 kg of water by 1^C
1 calorie = amount of ….
1 calorie = amount of heat needed to raise 1 gram of water by 1^C
1 CHU = the amount of
1 Celsius heat unit (CHU) = the amount of heat needed to raise the temperature of 1 lb of water by 1^C
If measuring very low temperatures up to -200^C what should you use?
A thermomteter with alcohol
Alcohol freezes at -200^C whereas Mercury freezes at -38^C
What is the freezing point of each of these?
Alcohol
Mercury
Therefore which is better for measuring cold temps?
Alcohol = -200^C freezing temp
Mercury = -34^C freezing temp
Alcohol is better use
What is the formula for specific heat capacity? (metric)
Q = (m)(C)(Change in T)
where Q = heat gained or lost
m = mass in kg
C = specific heat capacity in joules/kg
What is meant by latent heat of fusion?
The word latent means hidden
When the phase change is from solid to liquid we must use the latent heat of fusion
What is meant by latent heat of vaporisation?
Latent heat of vaporisation is the phase change from liquid to a gas
At what temperature should a refrigerant evaporate and condense? (low or high)
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)
What is heat?
Heat is the form of energy that is transferred between systems or objects with different tempeatures
What is meant by the term Sublimate?
A sublimate can go directly from a solid to a gas
What is an isothermal process and how is it accomplished in terms of surroundings?
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
Water is densist at what temperature?
4^C
What is meant by specific heat capacity?
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’’
What is true of a substance with a high specific heat capacity?
(temperature)
A substance with a high specific heat capacity can absorb a large quantity of heat before it will raise in temperature
