Physics/Chemistry Flashcards
What is a liquid?
- Heat added to change from solid into a liquid
- Kinetic energy not enough to overcome van der Waals forces - atoms move about but stay in non-fixed structure
What is a gas?
- more heat is added to change from a liquid to a gas
- Kindetic energy builds enough to break van der waal forces and atoms are free to move about
What is kinetic energy produced from?
All the atoms moving and colliding.
What is the definition of energy?
The ability to do work
What is the heat of fusion?
Potential energy increases and molecules can do work
Which state has the most potential energy? Why?
Gas - the molecules want to be close to each other but have so much energy, they can’t.
What is the scientific definition of equilibrium?
When energy transfer between 2 objects is equal
What is the definition of temperature?
Numerical ranking of hot or cold; the degree of hotness or coldness of a body.
What is the unit of measurement of temperature?
Kelvin/Celsius
What are properties of temperature?
Increases when heated
Decreases when cooled
What is the definition of heat?
Energy that is transferred as a result of a temperature difference/a form of energy which flows from a hotter region to a cooler region
What is the unit of measurement for heat?
Joule
What are properties of heat?
Flows from a hot area to a cold area.
What does critical temp mean?
Temp at which a substance can’t be liquefied no matter how much pressure is applied
Ex. Oxygen in cylinder will never be a liquid at room temp
What is the definition of boiling point?
Temp at which the vapor pressure of a liquid equals atmospheric pressure
What is the definition of absolute zero?
Temp at which no further heat energy can be extracted from any object
Ex. 237.25 C - temp at which all molecular motion stops
What is specific heat?
Amount of heat (energy) required to raise the temperature of 1 kg of a substance by 1 degree centigrade or kelvin
How many joules are in 1 calorie?
4.18 J
What is the heat of fusion?
Amount of heat necessary to convert (overcome van der Waal forces and allow molecules to move more freely) a solid into a liquid at its normal melting point
What is the heat of vaporization?
Amount of heat necessary to convert (overcome van der Waal forces and allow molecules to escape into a gas phase) a liquid into a gas at its normal boiling po
Why is it important to know the critical temperature of gases?
The pressure gauge can mean different things based on if the gas is the liquid phase or gas phase in the tank.
- O2 - gauge is linear
- N2O, can’t tell how much is left because pressure is always the same - need to weigh to determine how much is actually left
At what temp is N2O a gas?
97.7 F and above
At what temp is CO2 a gas?
88 F and above
At what temp is O2 a gas?
-119 F and above
What does critical pressure mean?
Minimum pressure necessary to liquefy a gas at its critical temp
What does conduction mean?
Transfer of heat between objects in direct contact with each other
Ex. Body against cold metal gets colder
What does convection mean?
The up and down movement of gases and liquids caused by heat transfer
Ex: Blair hugger increases temp
What does radiation mean?
Exchange of heat to an object through electromagnetic waves; objects do not need to touch to exchange heat
Ex. General loss of heat in uncovered patient
What is evaporation?
Dissipation of heat through skin (skin prep) and respiratory tract (exhalation)
Why is understanding the transfer of heat important in anesthesia?
We put the temp regulating part of the brain to sleep so patient can’t regulate their own temp and tend to drift towards room temp.
Cause vasodilation so more blood is coming to and near surface of skin to cool it down.
What is Boyle’s law?
P1V1=P2V2
As volume decreases, pressure increases
B is for barometric pressure balloon.
Example of Boyle’s law in anesthesia with inspiration and expiration.
During inspiration, intrapulmonary pressure falls, volume increases
During expiration, intrapulmonary pressure increases, volume decreases
What is Charles’ law?
V1/T1 = V2/T2
Temp up, volume up
C is for centigrade
Ex. Balloon: volume decreases when temp decreases
What is Guy-Lussac’s law?
P1/T1 = P2/T2
Temp up, pressure up
Ex: when a cylinder of gas is moved from a cool temp to a warmer temp, the pressure in the cylinder increases
What is Avagadro’s law?
One mole of a gas at standard temp (0 C) and pressure (1 atm or 760 mmHg) occupies a volume of 22.4L
What is Avogadro’s number?
6.02x10^23
What does Avogadro’s number mean?
Number of molecules in 1 gram molecular wt.
What is the ideal gas law?
PV=nRT
What is the pneumonic to remember all of the gas laws?
Can these guys possibly be violinists?!
What is Dalton’s law?
The total pressure in a mixture of gases is equal to the sum of the pressure of each individual gas
Partial pressure of O2 in atmosphere = atmospheric pressure x percent concentration
X = 760 mmHg x 21% O2
= 760 X .21
= 160 mmHg partial pressure of O2 at sea level
Total pressure = P1+P2+P3+…
D is for DPL (Dalton’s percentage law)
When gases are mixed, how are forces exerted?
Each gas exerts a force proportional to the number of molecules of the gas
What sets the gradient for diffusion?
Partial pressures
How do you calculate the current volume of gas in a cylinder?
Current volume = current pressure/full pressure x full volume
How do you calculate the current volume of liquid in a cylinder?
Current volume = current wt/full wt X full liquid
What does the reading on the pressure gauge of N2O mean?
- The amount of pressure that exists over the liquid in the tank - as gas escapes, liquid inside vaporizes and heat is lost (temp falls)
- As temp falls, reassure of gas decreases. When turned off, pressure is restored as cylinder regains heat from atmosphere
- If liquid runs out, pressure will fall rapidly.
How many L are in a full O2 cylinder?
660L
How many psi are in a full O2 cylinder?
2200 psi
Problem: full E cylinder, administering O2 per NC at 5 L/min. How long before the tank runs out? What about if you start with an 1100 PSI tank?
660L / 5 LPM = 132 min
330L / 5 LPM = 65 min
What is Henry’s Law?
The amount of gas that dissolves in a liquid is proportional to the partial pressure of the gas in the gas phase
H is for Heineken
How could we calculate how much O2 and CO2 is dissolved in the blood?
Henry’s law!
O2 dissolved in 100 cc blood = 0.003 partial pressure of O2
PaO2=200 mmHg
200X0.003=0.6 mL O2/100 mL blood
What is the a diabetic process?
Alteration of a state of gas without exchange of heat - only due to pressure
Ex: air over mountain
- Rises on windward side –> expands and cools
- Descends on leeward side –> compressed and warms
Why do we worry about adiabatic process in anesthesia?
Expansion in a pressurized situation
- If a cylinder of compressed gas is opened into a closed space (such as the anesthesia machine), the pressure and temp in the closed space will rise rapidly and could potentially cause a fire
What is woods metal?
Soft metal allows that mets at 200 degrees
Allows cylinder to exhaust rather than explode under excessive heat or pressure
What is the Joule-Thompson effect?
When compressed gas escapes freely into space (from pressure to non-pressure), adiabatic cooling occurs
What is Graham’s law?
Diffusion is directly proportional to molecular weight
Does CO2 diffuse faster or slower than O2?
Faster - about 20 times faster
When does equilibrium occur with inhalation agents?
When the partial pressure of the gas is the same everywhere
What is the definition of osmosis?
The movement of water from an area of high concentration to an area of low concentration through a semi-permeable membrane
What happens if you put a cell in a hypertonic solution?
Cell shrinks
What happens if you put a cell in a hypotonic solution?
Cell swells/rupture
What happens if you put a cell in an isotonic solution?
Stays the same
What is the 2nd gas effect?
The uptake of a volatile agent is increased when it is administered with N2O (which is very soluble in blood)
What is diffusion hypoxia?
Because N2O is so soluble, the alveoli fill up with it and dilutes alveolar O2 as it leaves the blood stream
What is pressure?
Force exerted per area - is the amount needed to open the aortic valve and push blood out.
What is tension?
The internal force generated by a structure. It is the active force the Herat must develop to eject blood
- Greater filling of LV (increases radius), causes a greater tension in the wall.
What is the law of Laplace (cylinder shapes)?
T=Pr
T= wall tension
P= pressure of liquid within the cylinder
R= radius
What is the law of Laplace (spheres)?
T=Pr/2
T= wall tension
P= pressure of liquid within the cylinder
R= radius
Where is surfactant produced?
Lipoprotein produced by type 2 alveolar cells
What does surfactant do?
Equalizes surface tension between 2 different sized alveoli and create more stable pressures. Explains why smaller alveoli don’t dump into larger alveoli under normal circumstances.
What has the greatest effect on flow?
Radius!
Doubling radius increases flow by how much?
16x’s
What is Poiseuille’s Law?
Flow is directly proportional to the 4th power of the radius
What are characteristics of laminar flow?
- flow is directly proportional to the hydrostatic pressure gradient
- Flow is inversely proportional to viscosity
- flow is inversely proportional to length of the tube
What are characteristics of resistance?
- resistance is inversely proportional to the r^4 (the greater the radius, the smaller the resistance)
- resistance is directly proportional to fluid viscosity (increased viscosity, increased resistance)
- Resistance is directly proportional to tube length
When does flow become turbulent?
- velocity of the flow is high
- tube wall is rough
- There are kinds, bends, or narrowing portions of the tube
- Fluid flows through an orifice
- the angle is greater or equal to 25 degrees.
What is Reynolds number?
Predicts when flow through a tube changes from laminar to turbulent
What is the formula to find Reynolds number?
Reynolds number (Re) = (velocity X density X diameter)/viscosity
What is the Bernoulli effect?
In a tube of varying diameter…
- The pressure is highest at the point of greatest diameter and lowest at the point of greatest constriction
- Flow is fastest at the point of greatest constriction and slowest at the point of greatest diameter.
What is the Venturi effect?
Flow of O2 increases with smaller diameter. As O2 flows through the narrow part of the Venturi mask, the velocity increases and causes a pressure drop. This pressure drop causes room air to be drawn in and increases the volume of gas.
What uses the principle of the Venturi effect?
Jet ventilation with Saunders valve
What is Newton’s law?
An object will move in a straight line unless another force is applied to it.
What is the equation for pressure?
Pressure = force/area
What direction does pressure act?
Pressure acts in all directions equally
What direction does force act?
Force acts in a given direction
What is a solid?
- Van der Waals forces hold atoms together
- The atoms move but stay in a fixed shape
