Thermodynamics

Question 1

Any and all substances can exist in 1 of these 4 states:

Answer 1

Solid
Liquid
Gas
Plasma

Question 2

State of matter is determined by what 2 things?

Answer 2

Temperature

Pressure

Question 3

Matter in a gaseous state has no definitive _____ or _____.

Answer 3

Size

Shape

Question 4

The process when a substance changes from a solid to a vapor.

Answer 4

Sublimination

Question 5

What are the 3 states of water?

Answer 5

Solid
Liquid
Gas

Question 6

Some scientist say heat is _____ _____.

Answer 6

Molecular motion

Question 7

Water in its natural state is in the liquid/solid form. By removing heat from a given quantity of water the molecules slow down/speed up and the cohesion and adhesion between the molecules decrease/increase pulling the molecules close together and increasing its density. If enough heat is removed, the water will reach its densest point at 39/49°F.

Answer 7

Liquid
Slow down
Increase
39°F

Question 8

When heat is added to water at atmospheric pressure, the molecules will decrease/increase in speed.

Answer 8

Increase

Question 9

What is used to identify heat quantity in the English measuring system?

Answer 9

British Thermal Unit (BTU)

Question 10

The specific heat of any substance is the amount of heat required to lower/raise 1 lb of the substance 1°F at a given temperature and pressure.

Answer 10

Raise

Question 11

A good conductor has a specific heat capacity of less than _____.

Answer 11

1.0

Question 12

The ability of a substance could get so cold that it’s molecules would cease to move and it could get no colder because there is no lower temperature.

Answer 12

Absolute zero

Question 13

What are the 3 ways heat transfer occurs?

Answer 13

Radiation
Conduction
Convection

Question 14

What is the ability of a substance to conduct heat or the rate of conduction?

Answer 14

Thermal conductivity

Question 15

If adding or removing heat causes a change in the temperature of a material, the heat is called what?

Answer 15

Sensible heat

Question 16

When we are changing water to gas (steam) the same conditions exist. In this case we are evaporating or vaporizing the liquid into its vapor or gaseous state. The heat required for this change of state is called what?

Answer 16

Latent heat of vaporization

Question 17

Between points C and D, 970 BTU/lb were added and the temperature did not change. This heat was required to change the water to steam. This heat is called _____ _____ _____. When cooling the steam to water, the latent heat removed is called the _____ _____ _____.

Answer 17

Latent heat of vaporization

Latent heat of condensation

Question 18

What is a fluid that picks up heat by evaporating at a low temperature and pressure and gives up heat by condensing at a higher temperature and pressure?

Answer 18

Refrigerant

Question 19

What do you call the temperature at which refrigerant oil change state from liquid to a vapor or vice versa?

Answer 19

Saturation temperature

Question 20

A substance is said to be at its critical point when it is at its critical/non-critical pressure and temperature when at this point the properties of a liquid and vapor are indistinguishable.

Answer 20

Critical

Question 21

Steam in its purest form is _____ to the eye.

Answer 21

Invisible

Question 22

What are the 2 kinds of steam?

Answer 22

Saturated

Superheated

Question 23

It’s temperature or heat content is above that of dry saturated steam at the same pressure.

Answer 23

Superheated steam

Question 24

What is the excepted reference temperature for enthalpy?

Answer 24

32°F

Question 25

What is the enthalpy of 1 pound of water at 212°F assuming zero enthalpy be at 32°F?

Answer 25

Specific heat of water is sp. ht. = 1BTU/lb/°F Heat to raise temperature of 1 pound of water from 32°F to 212°F = 212-32 = 180°F H=M x sp. ht. x 🔼T H=1 x 1 x 180 H=180 BTU (total enthalpy @ 212°F)

Question 26

What component is not on the high side?

Answer 26

Metering device

Question 27

What are the 4 basic components of a typical compression refrigeration system?

Answer 27

Evaporator Compressor Condenser Metering device

Question 28

The substance flowing around the evaporator tubes (air) is cooler/warmer than the refrigerant flowing through the tubes, so the substance transfers its heat to the refrigerant and leaves the evaporator at a higher/lower temperature than that at which it entered.

Answer 28

Warmer | Lower

Question 29

What is a coil of metal tubing that is exposed to air or water?

Answer 29

Condenser

Question 30

The absorbed heat comes from the air passing through the _____ fins.

Answer 30

Evaporator

Question 31

When the vapor reaches the _____, the condenser coil will be hotter than the outside air being forced through the condenser coil. The result will be a heat transfer from the coil to the outside air. This heat transfer removes the _____ _____ of the refrigerant vapor as it condenses and removes latent heat of condensation.

Answer 31

Condenser | Latent heat

Question 32

What is the reverse of evaporation whose purpose is to expel heat absorbed by the refrigerant?

Answer 32

Condensation

Question 33

What boils in the evaporator at low temperature as it absorbs heat from the air or from the substance that you want to cool?

Answer 33

Refrigerant

Question 34

In condensing, the refrigerant accepts/rejects the heat that it absorbed during boiling. The condensed liquid refrigerant is then metered back to the refrigerated area to absorb/dissolve more heat by boiling again.

Answer 34

Rejects | Absorbs