Atoms And Molecules Flashcards
What is the Maxwell-Boltzmann distribution?
The probability that a particle will have a given speed (presented graphically as a normal distribution with right skew)
How does temperature affect the maxwell-boltmann distribution
Increases kinetic energy therefore increases speed and moves curve to the right
Equation for kinetic energy of molecules
Ke = 1/2 mv squared
How does molecular weight affect speed in kinetic energy at a constant temperature
Heavier molecules have a slower speed
Equation for force
Which newton’s law is this
Force = mass x acceleration
This is newton’s second law
Equation for pressure and definition of pressure
Pressure = force/ total area
Force of gas particles colliding with container wall
Newton’s first law of motion
An object at rest remains at rest, and an object in motion continues in motion with a constant velocity
Newtons third law of motion
Every action has an equal and opposite reaction
Equation for momentum
P = mass x velocity
Units for force
Newton (1 newton gives a mass of 1kg an acceleration of 1 m/s squared)
SI unit for pressure
Pascal
One Newtown acting over 1 metre squared
Pressure conversion units = 1 atmosphere
101.3 kPa
1 bar
760 mmHg
A closed ended manometer will give an ____ pressure
Absolute
Boyles law
At a constant temperature, pressure is inversely related to volume
Charles law
At a constant pressure, temperature is directly proportional to volume
Guy Lussacs law
At a constant volume, the absolute pressure of a mass is directly proportional to absolute temperature in Kelvin
Avogrados principle
Equal volumes of all gases at the same temperature and pressure have the same number of molecules
What is a mole
Quantity of substance containing the same number of particles as there are atoms in 12g of carbon 12
Equal to 6.022x10 23
How many litres does one mole of gas occupy at standard temperature and pressure
22.4 L
Standard temperature and pressure
Temperature 273 K
Pressure 1 atm
Ideal gas law
What is R
PV = nRT
R = 8.31
Daltons Law
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
What is the critical temperature
The temperature above which a substance cannot be liquefied however much pressure is applied.
What is critical pressure
Vapour pressure of a substance at critical temperature
Saturated vapour pressure
The partial pressure exerted by the vapour at equilibrium
Henry’s Law
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)
How does temperature affect gas in solutions
As temperature increases, solubility decreases as the gas has more kinetic energy to bubble out of solution
Bunsen coefficient (solubility coefficient)
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
Ostwald coefficient (solubility coefficient)
Vol of gas dissolved in a unit vol of liquid at temperature concerned
Convert mmHg to kPa
÷ by 7.6
Convert Celsius to kelvin
Add 273
Partition coefficient
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.
Blood gas coefficients of volatile gases
Xenon 0.12
Desflurane 0.42
N2O 0.46
Sevoflurane 0.6
Isoflurane 1.4 (purple)
Enflurane 1.9 (orange)
Halothane 2.4 (red)
Density equation and units
p (rho) = mass / volume
kg/m3
Effect of increased pressure on density
Increasing pressure increases the number of particles in a given volume therefore increases density
Effect of temperature on density
Increasing temperature increases the kinetic energy of gases therefore have more energy to move apart and decreases density
Viscosity definition and units
The tendency of a fluid to resist flow
Measured in poise
What is a newtonian fluid
Viscosity dependant on temperature and pressure, it is unaffected by shear or tangential stress
Effect of temperature on viscosity
Increasing temperature increases kinetic energy and particles move apart therefore reduce viscosity
Ie oil moves around quicker in a pan as it heats
Effect of pressure on viscosity
Increasing pressure increases the number of molecules in a given volume therefore increases viscosity
Laminar flow equation
piPr4 / 8nl
Turbulent flow equation
P r2 / p (rho, density), l
How does a Wrights respirometer work
Measures flow by measuring gas volume over one minute
What type of flowmeter is a pneumotacograph?
How is it calibrated?
Constant orifice, variable pressure
Calibrated via known flow rate. Needs recalibration if change in temperature, pressure or gas.
How does a pneumotacograph work?
Laminar flow through small diameter tubes. Pressure difference between start and end of tubes measured and transduced.
What kind of flow meter is a rota meter
Constant pressure, variable orifice
How does a rota meter work
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.
Effect of density and viscosity in rota meter
Viscosity affects base (laminar flow) and density affects top of tube (turbulent flow)
Where should flow be measured from in
a) flat top bobbin
b) spherical bobbin
a) top
b) middle
What kind of flow meter is a PEFR?
Constant pressure, variable orifice
Boiling point and melting point of oxygen
-183 and -219 celcius
Critical temperature of oxygen
-119 degrees C
Boiling point and melting point of nitrogen
-88 and -91Celcius
Critical temperature of nitrous oxide
36.5
Critical pressure of nitrous oxide
72 bar
Boiling point and melting point of CO2
-79 and -57 degrees C
Critical temperature of CO2
30 degrees C
What does a higher SVP mean for vaporisation at the same temperature
At the same temperature a gas is more likely to vaporise ie isoflurane > sevoflurane
What happens when SVP equals atmospheric pressure
The liquid boils
How does temperature affect SVP
It increases in a non linear fashion
Define latent heat of vaporisation
The heat required to convert a given mass of liquid into vapour whilst maintaining the same temperature.
Difference between heat and temperature
Temperature is the hotness/ coldness of a substance
Heat is the energy required to change one phase to another
What is adiabatic (fast) change
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.
Why does a compressed gas which expands adiabatically cool?
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.
What is isothermal (slow) change?
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
Why do vaporizers lose heat
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.
Function of wicks
Increase surface area for vaporisation
Temperature compensation in vaporisers
- Bimetallic Strip - 2 metals with different limits of thermal expansion to partially open and close an orifice
- Heat sink - buffer latent heat loss
Effect of ambient pressure on svp
Does not change it
What is the latent heat of fusion Should temperature be specified
What are the units
The heat energy required to change state from solid to liquid.
Yes
J/kg
Critical pressure of CO2
73 bar
Triple point of water in Kelvin and sublimation pressure (SVP)
0.01K
4.6mmHg
How does entonox work
Bubble oxygen through liquid nitrogen, poynting effect, needs to be kept above -7 to prevent hypoxic mixture
What happens if entonox less than -7
Nitrous would liquefy (lamination/ seperation) leading to hypoxic mixture
How to prevent dangers of liquefaction of entonox (3)
- Store horizontally
- Maintain temperature
- Dip tube to ensure gas with most O2 delivered first
Explain oxygen storage
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.
How does a VIE work
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.
Vapour pressure in N20 cylinder
44 bar
Filling ratio of N2O
Weight of fluid in relation to weight of water if cylinder full. 0.75 in UK
Boiling points of desflurane
23 degrees
Define humidity
Amount of water vapour in a definite volume of gas
Define absolute humidity and units
Mass of water vapour/ volume of gas
g/m3
Relative humidity and units
Actual vapour pressure/ SVP
%
How does temperature affect humidity
It does not affect absolute humidity.
However it increases the SVP therefore decreases relative humidity.
Effect of higher humidity on temperature
Greater humidity, less likely water evaporates
Effect of pressure on humidity
Doesn’t change SVP
Increases water vapour pressure therefore relative humidity increases
What is the dew point what is its relationship with relative humidity
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.
What is a regnaults hygrometer
Silver tube containing ether.
Air is bubbled through which reduces temperature.
The temperature condensation forms on outside of tube is dew point.
How does a HME filter work?
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
How does a nebulizer work
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
Absoute humidity at room temperature
17 g/m3
Hydration shells form around larger non polar molecules in a cage like structure called
Clathrate formation
Define mixture, suspension and colloid
Mixture - dispersed but retain own identity (non homogeneous)
Suspension- separate out
Colloid - have internal and external phase, emulsions
Raoults law
Addition of a solute lowers the SVP of the solvent
Effect of increasing temp on solubility of a) solids b) gases
A) increases
B) decreases
The boiling point of water rises with solute added to it T or F
T
Define osmosis
Solvent moves across a semi permeable membrane from hypo to hypertonic concentration
Semi permeable membrane permeable to solvent not solution
Van’t Hoff equation
=iMRT
i factor
M molarity
How does peritoneal dialysis work
Solution of glucose and salt run into peritoneal cavity. Water and toxins move via osmosis through peritoneum and removed via catheter.
How does haemodialysis work
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
How does CVVH work
Uses convection to drive ions, fluid and small solutes across semi permeable membrane. Larger membrane pores (50kDa). Reinfusate replaces electrolytes.
Define heat energy
Total energy of molecular motion.
Define temperature
Average kinetic energy of atoms. Likelihood for one substance to transfer heat every to another.
Define specific heat capacity, equation and units
Amount of heat energy required to raise the temperature of 1kg by 1 Kelvin.
c = Q/ mT
kJ/ kg/ K
Heat capacity definition and equation
Raise temp of given object by 1 Kelvin
= SHC x weight
Four causes of heat loss
- Conduction (contact with surfaces)
- Convection (30%) (air surrounding patient warmed therefore rises and cooler air moved closer to patient
- Radiation (40%) electromagnetic waves
- Evaporation (20%)
- Humidification and warming of inspired gases (10%)
Factors affecting heat loss (three categories)
- Patient factors - babies large surface area, elderly decreased BMR/ lower muscle mass/ adipose tissue. Loss of physiological and behavioural response to hypothermia.
- Surgical factors - cool theatres, laminar flow, cavities exposed, cold irrigation.
- Anaesthetic factors - vasodilation, latent heat of vaporisation, use of cold IVT/ blood, may be paralysed.
Pascals principle
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.
Boiling point of sevo
59 degrees
Boiling point of isoflurane
48 degrees
Boiling point of enflurane
56 degrees
Boiling point of halothane
50 degrees
What does a hair hygrometer measure
Relative humidity
Absolute humidity in upper airways
33 g/m3
Absolute humidity at body temperature (37 degrees)
44 g/m3
What is an osmole
Number of moles in a compound contributing to total osmotic pressure
ie NaCl 2 osmoles
Glucose 1 osmose
Pressure in column of liquid equation (Stevins Law)
Effect of angled column on pressure
P = p(density) x gravity x height
Angle reduces pressure
