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E-lfh FRCA Primary: Physics - Atoms & Molecules in Motion > Density and Viscosity > Flashcards

Density and Viscosity Flashcards

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1
Q

What are the boiling, melting and critical temperatures of oxygen?

A

Boiling point: -183 C
Melting: - 219 C
Critical temp: -118

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2
Q

What is the critical pressure of oxygen?

A

50 bar

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3
Q

What is saturated vapour pressure (SVP) of oxygen at 20 C?

A

1.4 bar

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4
Q

What are the boiling, melting and critical temperatures of nitrous oxide?

A

Boiling point: -88 C
Melting: - 91 C
Critical temp: 36.5 C

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5
Q

What is the critical pressure of nitrous oxide?

A

72 bar

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6
Q

What is saturated vapour pressure (SVP) of nitrous oxide at 20 C?

A

50.8 bar

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7
Q

What are the boiling, melting and critical temperatures of carbon dioxide?

A

Boiling point: -79 C
Melting: - 57 C
Critical temp: 30 C

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8
Q

What is the critical pressure of carbon dioxide?

A

73 bar

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9
Q

What is saturated vapour pressure (SVP) of carbon dioxide at 20 C?

A

57 bar

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10
Q

What are the boiling, melting and critical temperatures of helium?

A

Boiling point: -269 C
Melting: - 272 C
Critical temp: - 268 C

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11
Q

What is the critical pressure of helium?

A

2.3 bar

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12
Q

Regarding the density of a gaseous substance (true or false):

Density is mass per unit volume measured in kg.m

A

False. Density is measured in kg/m3.

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13
Q

Regarding the density of a gaseous substance (true or false):

A decrease in pressure increases density

A

False. Increasing pressure leads to an increase in density.

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14
Q

Regarding the density of a gaseous substance (true or false):

An increase in temperature increases the kinetic energy of the molecules within gas and therefore increases the density

A

False. Decreasing temperature leads to an increase in density.

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15
Q

Regarding the density of a gaseous substance (true or false):

Density has a more marked effect on turbulent flow than viscosity does

A

True

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16
Q

Regarding the density of a gaseous substance (true or false):

Density has a more marked effect than viscosity on the flow at the base of a rotameter

A

False. The base of a rotameter has a narrow orifice around the bobbin causing laminar flow, which is more markedly affected by viscosity than density.

17
Q

Regarding the viscosity of a gaseous substance (true or false):

Viscosity is directly proportional to laminar flow

A

False. Viscosity is inversely proportional to laminar flow.

18
Q

Regarding the viscosity of a gaseous substance (true or false):

The viscosity of honey is greater than that of water

A

True.

19
Q

Regarding the viscosity of a gaseous substance (true or false):

An increase in temperature increases viscosity

A

False. Increasing temperature decreases viscosity, the ability of the substance to resist flow.

20
Q

Regarding the viscosity of a gaseous substance (true or false):

An increase in pressure leads to an increase in viscosity

A

True

21
Q

Regarding the viscosity of a gaseous substance (true or false):

A fluid with higher viscosity improves laminar flow, given fixed tube length and radius and pressure gradient

A

False. Increasing viscosity reduces laminar flow.

22
Q

Regarding flowmeters (true or false):

A pneumotachograph is an example of a fixed orifice, variable pressure device

A

True

23
Q

Regarding flowmeters (true or false):

A rotameter relies on the constant pressure drop supporting the weight of the bobbin

A

True

24
Q

Regarding flowmeters (true or false):

A Wright’s Respirometer is used to measure flow

A

False. A Wright’s Respirometer is used to measure volume; only with the addition of a timing device can it measure flow.

24
Q

Regarding flowmeters (true or false):

A peak expiratory flowmeter is an example of a constant pressure variable orifice device

A

True

25
Q

Regarding flowmeters (true or false):

A Bourdon gauge can be used to calculate flow if a timing device is also used

A

False. A Bourdon aneroid gauge is used to measure pressure.

26
Q

Which of the following best describes the effect of changes on flow measurement near the top of a rotameter?

A. An increase in gas density causes the bobbin to rotate less
B. A decrease in viscosity leads to an increase in laminar flow
C. The pressure difference across a rotameter bobbin is constant
D. An increase in gas temperature decreases the density of the gas and increases flow
E. The flow measurement should be read from the top of the bobbin

A

D. This statement is the best fit because it describes the effect of a change in gas density on the more turbulent flow found at the top of a rotameter.

A. Incorrect. An increase in density reduces flow and, therefore, causes the bobbin to rotate less. However, the rotation of the bobbin does not affect the measurement of flow.

B. Incorrect. Decreased viscosity causes an increase in laminar flow, but laminar flow is found mostly at the base of the rotameter where the orifice is small.

C. Incorrect. The pressure difference across the bobbin, with the weight of the bobbin pressing down and gas pressure pushing up, is constant and will not affect changes in flow measurement.

E. Incorrect. The flow measurement should be read from the top of a flat-topped bobbin and from the middle of a spherical bobbin, neither of which affects changes in flow measurement at the top of a rotameter.

27
Q

The boiling point of oxygen is:

A. -183 C
B. -88 C
C. -269 C

A

A. Correct.

B. Incorrect. -88C is the boiling point of nitrous oxide.

C. Incorrect. -269C is the boiling point of helium.

28
Q

The critical temperature of nitrous oxide is:

A. 72C
B. 30C
C. 36.5C

A

A. Incorrect. 72 bar is the critical pressure of nitrous oxide.

B. Incorrect. This is the critical temperature of carbon dioxide. It is similar to the critical temperature of nitrous oxide which is why they can both be condensed to liquids.

C. Correct.

29
Q

What will happen to the flow if the temperature is increased in laminar flow?

A. The flow will increase
B. The flow will decrease
C. The flow will remain the same

A

A. The flow will increase

Laminar flow is affected by the factors in the Hagen-Poiseuille equation:

Laminar flow = ∆Pr4∏/8lη

Where ∆P is the pressure difference from the start of the flow to the end; r is the radius of the tube; l is the length of the tube and η (Greek symbol Eta) is the fluid viscosity.

Temperature reduces viscosity and hence increases flow.

30
Q

What will happen to the flow if the pressure gradient is increased in laminar flow?

A. The flow will increase
B. The flow will decrease
C. The flow will remain the same

A

A. The flow will increase

Laminar flow is affected by the factors in the Hagen-Poiseuille equation:

Laminar flow = ∆Pr4∏/8lη

Where ∆P is the pressure difference from the start of the flow to the end; r is the radius of the tube; l is the length of the tube and η (Greek symbol Eta) is the fluid viscosity.

A pressure gradient increase describes a variation in pressure applied to the flow of fluid and is not the same as consistent pressure increase. Adding a pressure bag to a litre of fluid increases the rate of flow; this is an increased pressure gradient.

31
Q

What will happen to the flow if the viscosity is reduced in laminar flow?

A. The flow will increase
B. The flow will decrease
C. The flow will remain the same

A

A. The flow will increase

Laminar flow is affected by the factors in the Hagen-Poiseuille equation:

Laminar flow = ∆Pr4∏/8lη

Where ∆P is the pressure difference from the start of the flow to the end; r is the radius of the tube; l is the length of the tube and η (Greek symbol Eta) is the fluid viscosity.

32
Q

What will happen to the flow if the temperature is increased in turbulent flow?

A. The flow will increase
B. The flow will decrease
C. The flow will remain the same

A

A. The flow will increase

Turbulent flow is proportional to r2 and √∆P and inversely proportional to length of the tube and density of the fluid.

Temperature reduces density and therefore increases flow.

33
Q

What will happen to the flow if the pressure gradient is increased in turbulent flow?

A. The flow will increase
B. The flow will decrease
C. The flow will remain the same

A

A. The flow will increase

Turbulent flow is proportional to r2 and √∆P and inversely proportional to length of the tube and density of the fluid.

Increasing the pressure gradient increases turbulent flow but not as much as laminar flow, because the streamlining is lost.

34
Q
A

E-lfh FRCA Primary: Physics - Atoms & Molecules in Motion (14 decks)

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