Lecture 2.2: Physics of Gases Flashcards
What is the Role of The Respiratory System?
• Serves to ensure that all tissues receive the oxygen they need
• And can dispose of the CO2 they produce
• Blood carries gases to and from tissues
• Lungs exchange with atmosphere
What is the Kinetic Theory of Gases?
• Gases are a collection of molecules moving around a space
• Pressure is generated by collisions of molecules with the walls
• The more frequent and harder the collisions the higher the pressure
How to calculate Pressure?
• Pressure = Force / per unit area
• i.e. 1 Newton (N) of force /square metre (m2) = 1 Pascal (Pa)
What other way can Pressure be expressed?
Pressure may also be expressed in mmHg (e.g. Blood Pressure of 120/80 mmHg),
How much is 1kPa in mmHg
7.5 mmHg
How much is 100mmHg in kPa?
13.3kPa
How much is 1 standard atmosphere in mmHg and kPa?
• 760 mmHg
• 101.1 KPa
What is Boyle’s Law?
• Pressure inversely proportional to volume
• If a given amount of gas is compressed into a smaller volume molecules will hit
the wall more often and pressure will rise
What is Charles’s Law?
• Kinetic energy of molecules increases with temperature
• As temperature increases molecules hit walls more often so pressure increases
• Pressure proportional to absolute temperature
• Scale starts at -273 deg C absolute zero
What is the Universal Gas Law?
• P.V=R.T
• Allows calculation of how volume will change as pressure and temperature
changes
What are Partial Pressures?
• In a mixture if gases molecules of each type behave independently
• They don’t chemically interact
• So each gas exerts a partial pressure
• Calculated as the same fraction of the total pressure as the volume fraction of
the gas in the mixture
What is Saturated Vapour Pressure?
• In biological systems gas mixtures always in contact with water
• So water molecules evaporate gas molecules dissolve
• Vapour pressure
• Depends only on temperature
• -6.28 kPa at 37 deg C
The amount of gas which enters the liquid to establish a particular
tension is determined by………..?
Solubility
What is the Equation to calculate Content?
Content = Solubility x Tension