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Sarah's Physics > Atoms And Molecules > Flashcards

Atoms And Molecules Flashcards

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1
Q

What is the Maxwell-Boltzmann distribution?

A

The probability that a particle will have a given speed (presented graphically as a normal distribution with right skew)

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2
Q

How does temperature affect the maxwell-boltmann distribution

A

Increases kinetic energy therefore increases speed and moves curve to the right

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3
Q

Equation for kinetic energy of molecules

A

Ke = 1/2 mv squared

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4
Q

How does molecular weight affect speed in kinetic energy at a constant temperature

A

Heavier molecules have a slower speed

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5
Q

Equation for force
Which newton’s law is this

A

Force = mass x acceleration

This is newton’s second law

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6
Q

Equation for pressure and definition of pressure

A

Pressure = force/ total area

Force of gas particles colliding with container wall

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7
Q

Newton’s first law of motion

A

An object at rest remains at rest, and an object in motion continues in motion with a constant velocity

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8
Q

Newtons third law of motion

A

Every action has an equal and opposite reaction

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9
Q

Equation for momentum

A

P = mass x velocity

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10
Q

Units for force

A

Newton (1 newton gives a mass of 1kg an acceleration of 1 m/s squared)

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11
Q

SI unit for pressure

A

Pascal

One Newtown acting over 1 metre squared

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12
Q

Pressure conversion units = 1 atmosphere

A

101.3 kPa
1 bar
760 mmHg

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13
Q

A closed ended manometer will give an ____ pressure

A

Absolute

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14
Q

Boyles law

A

At a constant temperature, pressure is inversely related to volume

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15
Q

Charles law

A

At a constant pressure, temperature is directly proportional to volume

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16
Q

Guy Lussacs law

A

At a constant volume, the absolute pressure of a mass is directly proportional to absolute temperature in Kelvin

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17
Q

Avogrados principle

A

Equal volumes of all gases at the same temperature and pressure have the same number of molecules

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18
Q

What is a mole

A

Quantity of substance containing the same number of particles as there are atoms in 12g of carbon 12

Equal to 6.022x10 23

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19
Q

How many litres does one mole of gas occupy at standard temperature and pressure

A

22.4 L

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20
Q

Standard temperature and pressure

A

Temperature 273 K
Pressure 1 atm

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21
Q

Ideal gas law
What is R

A

PV = nRT

R = 8.31

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22
Q

Daltons Law

A

In a mixture if gases, the pressure exerted by each gas is the same that which it would exert if it occupied the container alone

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23
Q

What is the critical temperature

A

The temperature above which a substance cannot be liquefied however much pressure is applied.

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24
Q

What is critical pressure

A

Vapour pressure of a substance at critical temperature

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25
Q

Saturated vapour pressure

A

The partial pressure exerted by the vapour at equilibrium

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26
Q

Henry’s Law

A

At a fixed temperature, the amount of a given gas dissolved in a given liquid is directly proportional to the partial pressure of the gas in equilibrium with the liquid

(Higher pressure, more dissolved gas)

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27
Q

How does temperature affect gas in solutions

A

As temperature increases, solubility decreases as the gas has more kinetic energy to bubble out of solution

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28
Q

Bunsen coefficient (solubility coefficient)

A

At STP, the volume of gas dissolved in a unit volume of a liquid where the PP of gas above the liquid is 1 atmosphere

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29
Q

Ostwald coefficient (solubility coefficient)

A

Vol of gas dissolved in a unit vol of liquid at temperature concerned

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30
Q

Convert mmHg to kPa

A

÷ by 7.6

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31
Q

Convert Celsius to kelvin

A

Add 273

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32
Q

Partition coefficient

A

Ratio of the concentration of a substance in one medium or phase (C1) to the concentration in a second phase (C2) when the two concentrations are at equilibrium.

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33
Q

Blood gas coefficients of volatile gases

A

Xenon 0.12

Desflurane 0.42
N2O 0.46

Sevoflurane 0.6

Isoflurane 1.4 (purple)

Enflurane 1.9 (orange)

Halothane 2.4 (red)

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34
Q

Density equation and units

A

p (rho) = mass / volume

kg/m3

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35
Q

Effect of increased pressure on density

A

Increasing pressure increases the number of particles in a given volume therefore increases density

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36
Q

Effect of temperature on density

A

Increasing temperature increases the kinetic energy of gases therefore have more energy to move apart and decreases density

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37
Q

Viscosity definition and units

A

The tendency of a fluid to resist flow

Measured in poise

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38
Q

What is a newtonian fluid

A

Viscosity dependant on temperature and pressure, it is unaffected by shear or tangential stress

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39
Q

Effect of temperature on viscosity

A

Increasing temperature increases kinetic energy and particles move apart therefore reduce viscosity

Ie oil moves around quicker in a pan as it heats

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40
Q

Effect of pressure on viscosity

A

Increasing pressure increases the number of molecules in a given volume therefore increases viscosity

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41
Q

Laminar flow equation

A

piPr4 / 8nl

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42
Q

Turbulent flow equation

A

P r2 / p (rho, density), l

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43
Q

How does a Wrights respirometer work

A

Measures flow by measuring gas volume over one minute

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44
Q

What type of flowmeter is a pneumotacograph?

How is it calibrated?

A

Constant orifice, variable pressure

Calibrated via known flow rate. Needs recalibration if change in temperature, pressure or gas.

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45
Q

How does a pneumotacograph work?

A

Laminar flow through small diameter tubes. Pressure difference between start and end of tubes measured and transduced.

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46
Q

What kind of flow meter is a rota meter

A

Constant pressure, variable orifice

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47
Q

How does a rota meter work

A

Pressure from gas flow, introduced by a needle valve, moves a bobbin in a tapered tube until it is counteracted by gravity.
Turbulent flow prevails at the top and laminar at the bottom.

48
Q

Effect of density and viscosity in rota meter

A

Viscosity affects base (laminar flow) and density affects top of tube (turbulent flow)

49
Q

Where should flow be measured from in
a) flat top bobbin
b) spherical bobbin

A

a) top
b) middle

50
Q

What kind of flow meter is a PEFR?

A

Constant pressure, variable orifice

51
Q

Boiling point and melting point of oxygen

A

-183 and -219 celcius

52
Q

Critical temperature of oxygen

A

-119 degrees C

53
Q

Boiling point and melting point of nitrogen

A

-88 and -91Celcius

54
Q

Critical temperature of nitrous oxide

A

36.5

55
Q

Critical pressure of nitrous oxide

A

72 bar

56
Q

Boiling point and melting point of CO2

A

-79 and -57 degrees C

57
Q

Critical temperature of CO2

A

30 degrees C

58
Q

What does a higher SVP mean for vaporisation at the same temperature

A

At the same temperature a gas is more likely to vaporise ie isoflurane > sevoflurane

59
Q

What happens when SVP equals atmospheric pressure

A

The liquid boils

60
Q

How does temperature affect SVP

A

It increases in a non linear fashion

61
Q

Define latent heat of vaporisation

A

The heat required to convert a given mass of liquid into vapour whilst maintaining the same temperature.

62
Q

Difference between heat and temperature

A

Temperature is the hotness/ coldness of a substance
Heat is the energy required to change one phase to another

63
Q

What is adiabatic (fast) change

A

The state of a gas is altered without a change in heat energy to or from the gas and its surroundings. Therefore heat comes from gas itself therefore cools.

64
Q

Why does a compressed gas which expands adiabatically cool?

A

Energy is required for gas molecules to move.
No heat is exchanged with the gases surroundings so the energy must come from the molecules own kinetic energy.

65
Q

What is isothermal (slow) change?

A

Compression or expansion of a gas occurs slow enough for heat to be transferred from the wall of the container so gas temperature remains the same

66
Q

Why do vaporizers lose heat

A

Volatile agents lose heat as they are vaporised.
The temperature of remaining fluid falls lowering its SVP which reduces output so temperature compensation is required.

67
Q

Function of wicks

A

Increase surface area for vaporisation

68
Q

Temperature compensation in vaporisers

A
  1. Bimetallic Strip - 2 metals with different limits of thermal expansion to partially open and close an orifice
  2. Heat sink - buffer latent heat loss
69
Q

Effect of ambient pressure on svp

A

Does not change it

70
Q

What is the latent heat of fusion Should temperature be specified
What are the units

A

The heat energy required to change state from solid to liquid.

Yes

J/kg

71
Q

Critical pressure of CO2

A

73 bar

72
Q

Triple point of water in Kelvin and sublimation pressure (SVP)

A

0.01K
4.6mmHg

73
Q

How does entonox work

A

Bubble oxygen through liquid nitrogen, poynting effect, needs to be kept above -7 to prevent hypoxic mixture

74
Q

What happens if entonox less than -7

A

Nitrous would liquefy (lamination/ seperation) leading to hypoxic mixture

75
Q

How to prevent dangers of liquefaction of entonox (3)

A
  1. Store horizontally
  2. Maintain temperature
  3. Dip tube to ensure gas with most O2 delivered first
76
Q

Explain oxygen storage

A

Liquid oxygen requires cooling system below its critical temperature of -118, held under a vacuum (VIE) with a heating and pressure regulating system to allow gas to expand before delivery.

77
Q

How does a VIE work

A

Oxygen vapour channelled through heat exchanger and pressure regulators (1000kpa and 414kpa).
As oxygen is used, the liquid cools.

If no O2 used the temperature rises increasing the pressure and blown off through pressure safety valve.

Heavy demand causes pressure to drop so liquid O2 passes through pressure raising vaporiser and returned in gaseous form.

78
Q

Vapour pressure in N20 cylinder

A

44 bar

79
Q

Filling ratio of N2O

A

Weight of fluid in relation to weight of water if cylinder full. 0.75 in UK

80
Q

Boiling points of desflurane

A

23 degrees

81
Q

Define humidity

A

Amount of water vapour in a definite volume of gas

82
Q

Define absolute humidity and units

A

Mass of water vapour/ volume of gas

g/m3

83
Q

Relative humidity and units

A

Actual vapour pressure/ SVP

%

84
Q

How does temperature affect humidity

A

It does not affect absolute humidity.
However it increases the SVP therefore decreases relative humidity.

85
Q

Effect of higher humidity on temperature

A

Greater humidity, less likely water evaporates

86
Q

Effect of pressure on humidity

A

Doesn’t change SVP
Increases water vapour pressure therefore relative humidity increases

87
Q

What is the dew point what is its relationship with relative humidity

A

The temperature a given volume of gas must be cooled in order for water vapour to condense out - the point 100% relative humidity.
The higher the relative humidity the less temperature drop required to reach dew point.

88
Q

What is a regnaults hygrometer

A

Silver tube containing ether.
Air is bubbled through which reduces temperature.
The temperature condensation forms on outside of tube is dew point.

89
Q

How does a HME filter work?

A

Internal material has hygroscopic substance.
When water vapour passes through it condenses to provide latent heat.
This heat is used to warm the cooler inspired air on next breath.

Max 35 g/m3

90
Q

How does a nebulizer work

A

Uses venturi effect to entrain water along a capillary tube to form droplets that are then carried in the gas flow

Ultrasonic - water dropped on to a vibrating plate

91
Q

Absoute humidity at room temperature

A

17 g/m3

92
Q

Hydration shells form around larger non polar molecules in a cage like structure called

A

Clathrate formation

93
Q

Define mixture, suspension and colloid

A

Mixture - dispersed but retain own identity (non homogeneous)
Suspension- separate out
Colloid - have internal and external phase, emulsions

94
Q

Raoults law

A

Addition of a solute lowers the SVP of the solvent

95
Q

Effect of increasing temp on solubility of a) solids b) gases

A

A) increases
B) decreases

96
Q

The boiling point of water rises with solute added to it T or F

A

T

97
Q

Define osmosis

A

Solvent moves across a semi permeable membrane from hypo to hypertonic concentration

Semi permeable membrane permeable to solvent not solution

98
Q

Van’t Hoff equation

A

=iMRT

i factor
M molarity

99
Q

How does peritoneal dialysis work

A

Solution of glucose and salt run into peritoneal cavity. Water and toxins move via osmosis through peritoneum and removed via catheter.

100
Q

How does haemodialysis work

A

Blood pumped out and exposed to selectively permeable membrane with dialysate solution on other side. Small solutes but not large proteins diffuse through in countercurrent to increase efficiency

101
Q

How does CVVH work

A

Uses convection to drive ions, fluid and small solutes across semi permeable membrane. Larger membrane pores (50kDa). Reinfusate replaces electrolytes.

102
Q

Define heat energy

A

Total energy of molecular motion.

103
Q

Define temperature

A

Average kinetic energy of atoms. Likelihood for one substance to transfer heat every to another.

104
Q

Define specific heat capacity, equation and units

A

Amount of heat energy required to raise the temperature of 1kg by 1 Kelvin.

c = Q/ mT
kJ/ kg/ K

105
Q

Heat capacity definition and equation

A

Raise temp of given object by 1 Kelvin
= SHC x weight

106
Q

Four causes of heat loss

A
  1. Conduction (contact with surfaces)
  2. Convection (30%) (air surrounding patient warmed therefore rises and cooler air moved closer to patient
  3. Radiation (40%) electromagnetic waves
  4. Evaporation (20%)
  5. Humidification and warming of inspired gases (10%)
107
Q

Factors affecting heat loss (three categories)

A
  1. Patient factors - babies large surface area, elderly decreased BMR/ lower muscle mass/ adipose tissue. Loss of physiological and behavioural response to hypothermia.
  2. Surgical factors - cool theatres, laminar flow, cavities exposed, cold irrigation.
  3. Anaesthetic factors - vasodilation, latent heat of vaporisation, use of cold IVT/ blood, may be paralysed.
108
Q

Pascals principle

A

Pressure is transmitted equally and undiminished through a compressed fluid. Angle fluid escapes from is perpendicular and uniform throughout multiple openings. It is not related to where pressure is applied.

109
Q

Boiling point of sevo

A

59 degrees

110
Q

Boiling point of isoflurane

A

48 degrees

111
Q

Boiling point of enflurane

A

56 degrees

112
Q

Boiling point of halothane

A

50 degrees

113
Q

What does a hair hygrometer measure

A

Relative humidity

114
Q

Absolute humidity in upper airways

A

33 g/m3

115
Q

Absolute humidity at body temperature (37 degrees)

A

44 g/m3

116
Q

What is an osmole

A

Number of moles in a compound contributing to total osmotic pressure

ie NaCl 2 osmoles
Glucose 1 osmose

117
Q

Pressure in column of liquid equation (Stevins Law)

Effect of angled column on pressure

A

P = p(density) x gravity x height

Angle reduces pressure

Sarah's Physics (6 decks)

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