SI units for pressure
Pascals Kg/ m x sec 2
Si units of Temperature
Kelvin = Centigrade + 273
All substances are made of atoms
• In solid state the atoms are suspended in a lattice.
• Adding heat increases the motion of atoms and eventually a change of state occurs.
are perfect gas, but is a hypothetical gas.
Consists of identical particles of zero volume & No intermolecular forces.
Constituent atoms or molecules undergo perfectly elastic collisions with the walls of the container.
- This approximation is often good enough to describe real gases.
- This breaks down at high pressures and low temperatures,
At a constant temperature the volume of a given mass of gas varies inversely with the absolute pressure. P1/V2 =P2/V2
At constant pressure the volume of a given mass varies directly with temperature.
(2nd gas law)
V1/T1 = V2/T2
Gay Lussac's Law
At constant Volume the absolute Pressure of a given mass varies directly with the absolute Temp.
(3rd gas law)
P1/T1 = P2/T2
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Pressure Temperature Volume = constant
Charles Boyles Gay-Lussac's = laws
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Boyle's law (corner B)
. relates Pressure and Volume (adjacent sides) at constant Temperature (opposite side).
. Charles' law (corner C)
relates Temperature and Volume (adjacent sides) at constant Pressure (opposite side).
.Gay-Lussac's law (corner G)
relates Temperature and Pressure (adjacent sides) at constant Volume (opposite side).
The law states that the product of the volume of a gas and its pressure over the temperature is equal to a constant.
P1 * V1/ T1 = K
When to use Combined Law?
For comparing the same substance under two different sets of conditions, the law can be
written as: P1 x V1/ T1= P2 x V2/ T2
6.022×10 23 particles per mole.
Equal volumes of gases, at the same temperature and pressure, contain the same number of particles, or molecules.
The ideal gas constant has the same value for all gases.
One moles of an ideal gas occupies 22.4 liters (dm3) at STP.
Ideal Gas Law
The state of an amount of gas is determined by its pressure, volume, and temperature.
Ideal Gas Law "R"
is the gas constant 8.314472 [m 3·Pa/(K * mol)]
Dalton's Law of Partial Pressures
P1 + P2 + P3 ... = P total
Are examples of exponential process.
eg. Imagine a muddy liquid being washed out with a continuous flow of water after a period of time the muddiness is removed.
Examples of Exponential functions (x5)
Basis of Dye Dilution technique
Thermo dilution technique.
Used to measure cardiac output.
Used to measure concentration. of drugs in the body.
Nitrogen washout curve
Time that it takes the quantity measured to decrease by 50%
Time it takes for the process to end assuming the first rate of change continued (time it would take for the stuff to disappear if it went on the original rate)
Greek Letter Tau denotes it.
• Process is 95% completed by three times constants.
Equation to calculate Half life from time constant
Half life = time constant log e2 = time constant 0.693
Positive Exponential Process
Starts out very slowly and as time builds up, the Quantity increases exponentially.
eg. Bacterial growth.
Build up Exponential Process
Things happen relatively quickly at first and as the quantity increases, the process slows down finally reaching a maximum.
eg Elimination half life.
Temperature above which a substance cannot be liquefied no matter how much pressure is applied.
What OR gas is critical temp especially important for?
What is the critical temp for Nitrous oxide
These are processes that commonly occur due to a change in the pressure of a gas.
Occurs when the pressure of a gas is increased.
An example of this is what goes on in a bicycle pump.
Occurs when the pressure of a gas is decreased, such as when it expands into a larger volume.
. i.e. the warning on caned air for removing dust from computers.
What can cause an Adiabatic explosion?
Opening a high pressure cylinder into a closed space suddenly may cause temperature to increase and ignite.
- Ex. Opening manifold of big tank of N20 in into a wall.
Joule Thompson Effect
Gas from a high pressure cylinder is allowed to escape into space.
As the gas expands it cools adiabatically.
• Decrease in pressure = decrease in temperature
Oxygen tank (color, pressure max L)
Green, 2200 psi, 660 L
Nitrous Oxide tank (color, pressure max L)
blue, 745 psi. 1590 L
(pressure on pressure gauge will not change until all liquid is gone than it will drop suddenly)
Air tank (color, pressure max L)
Yellow, 1900 psi, 625 L
Refers to the ability for a given substance,(the solute) to dissolve in a solvent.
what is a saturated solution?
It is the maximum amount of solute dissolved in a solvent at equilibrium.
At a particular temp the amount of a given gas dissolves in a given liquid is directly proportional to the partial pressure of the gas in equilibrium with the liquid.
Henry's law only applies when what is constant?
(because as temp increases less gas dissolves in liquid.)
Defined as the ration of the amount of substance present in one phase compared with another, the two phases being of equal volume and equilibrium.
Second Gas Effect
this happens because N2O is absorbed by bloodstream faster than O2 and nitrogen. thus during inspiration more oxygen and nitrogen are available in lung than originally expected.
Opposite occurs during expiration witch leads to diffusion hypoxia, need O2 during extubation phase.
Process by which the molecules of a substance transfer through a layer of area such as the surface of a solution.
Factors that affect diffusion
Molecular size, gradients, membrane area and thickness.
Rate of diffusion of a substance across a unit area is proportional to the concentration gradient.
Diffusion rate = reciprocal of the square root of the molecular weight
moles per liter
Moles per kg
Osmotic pressure related to proteins
Depression of vapor pressure of a solvent is proportional to the molar concentration of solute
is a mixture which vaporizes in the same proportion as its constituents volume proportions
eg alcohol and water 96% alcohol and 4% water
Joule (SI units)
one joule of work is done when a force of one newton moves its point of application one meter in the direction of force
Work= force * distance
Rate of work measured in Watts
one watt = 1J/second
is a form of energy that transfers from hotter to cooler substances
energy is in the form of kinetic energy
Thermal state of a substance, determines whether heat will flow to or from the substance.
body temperature below 35 degrees Celsius (can be lethal)
At what temp dose impairment occur?
At what temp does it become impairment become irreversible?
at 42 degrees cerebral impairment may occur
at 45 degrees it may be irreversible because of cascade effect.
May occur when skin at or higher than 45 degrees for prolonged time (burns are more likely in avascular portions of body)
Specific Heat Capacity
is the amount of heat required to raise the temp of 1 kg of a substance by 1 kelvin .
(SI unit of... is J/(Kg * K)
is the amount of heat required to raise the temperature of a given object by 1 kelvin.
(SI unit of ... is J/K)
Total heat capacity calculation
Specific heat capacity = 3.5 KJ/ (Kg * C).
in a 70 Kg patient = 3.5 x 70= 245 KJ/ C.
this means to change the temp of a 70 kg person by one degree 245 KJ must be added or removed.
Specific Heat of Water
4.15 KJ/ (C*K Kg)
remember 4.81 Joules = 1 calorie
4.18 KJ = 1 Kilocaorie = 1 C
Latent Heat of Vaporization
Is when a substance changes state from a liquid to a gas.
Is a Change of state without a change in temperature, requires energy.
Specific Latent Heat
the heat required to convert 1 Kg of a substance from one phase to another at a give temperature.
(SI units J/Kg)
Body temperature levels
may account for up to 50% heat loss
hot objects release radiant heat
cool objects absorb radiant heat.
It depends on temperature gradient (relative temperatures of surrounding objects).
metallic hats prevent loss of radiant heat
adjacent layers of liquid or gas is heated, following temperature gradient until equalization.
trapping of air or liquid prevents loss through convection
wet suit analogy.
due to loss of latent heat of evaporation
dependent on water vapor pressure gradient from skin to air.
total area of skin exposed is a factor.
sweating may increase heat loss X 10.
respiration and hypothermia
body must use 15% of its 80W just to humidify and warm anesthetic gases + oxygen.