S.I. units Gases and Gas Laws By Ahmed Ibrahim ; M.D. Prof.of Anesthesia Ain Shams University Anesthesia Department

© I L O Intended Learning Outcomes By the end of this lecture, the student will be able to: 1..know different units used for clinical measurements. 2..understand different laws controlling ideal gas behavior. 3..interpret the applications of different gas laws in anesthetic practice.

Meter m length Kilogram Kg mass Second s time Ampere A electric current Kelvin o K temperature Mole mol amount of substance Candela cdluminous intensity Basic 7 S.I units

Fractions & Multiples ,10 -15,10 -12,10 -9,10 -6,10 -3,10 -2, attofemtopiconanomicromillicentidecidecahectokilomegagigaterapentaexa afpnµmcdDahKMGTPE

aream2m2 volume m3m3 velocitydisplacement / timems -1 accelerationvelocity / time ms -2 forcemass x accelerationKgms -2 Newton N work (energy)force x distanceKgm 2 s -2,NmJoule J powerwork / timeKgm 2 s -3,Js -1 Watt W pressureforce / areaNm -2 Pascal Pa frequencycycles / secondHertz Hz electric chargeelectric current x timeCoulomb C potential difference (EMF) Volt V electric resistancepotential difference / currentOhm Ω electric capacitanceFarad F magnetic fluxWeber Wb

SOLIDLIQUIDGAS/VAPOUR I.M.FORCE I.M.SPACE MOLECULAR MOTION ±+++++ SHAPE OF CONTAINERNOYES MISSIBILITYNOYES VAPOUR gaseous state of the substance which is present in the liquid form at RTP GAS a substance which cannot exist in the liquid form at RTP

Kinetic Theory of Gases GAS MOLECULES are: Widely separated (negligible molecular volume) In constant motion (diffusion) In constant striking (pressure) IDEAL (PERFECT) GAS, obeys the 3 assumptions

GAS VOLUME PRESSURETEMP

Robert Boyle ( )., Ireland

Jacques Charles ( ) Critical Temperature “ the temperature above which a gas cannot be liquefied whatever pressure is applied ” Critical Pressure ” the pressure needed to liquefy a gas at its critical temperature “ N.B. in T in P needed CO 2 31 o C N 2 O36.5 o C (C.P = 74 atm) O o C

Joseph Louis Gay-Lussac ( )

for a given mass of a gas, at a constant: TEMPERATUREPRESSUREVOLUME V  1/P P x V =Const. P 1 xV 1 = P 2 xV 2 V  T( o A) V=T x Const. (K) V/T = K P  T Boyle’s lawCharles' lawGay-Lussac’s law

a Perfect Gas,is the one  that always obey Boyle’s and Charles’ laws.  in which the intermolecular forces and molecular volume are too small ( negligible ). a Real Gas behaves approximately as a perfect gas especially at low pressures and high temperatures. Equation of state of a perfect gas: V  1/P V  T V  T/P V = T/P x const PV/T = const (R) P 1 V 1 / T 1 = P 2 V 2 / T 2

Avogadro’s hypothesis Volumes for perfect gases at EQUAL Temp contain equal number of molecules Pressure 1 mole of any gas at, STP22.4 L Room temp24.1 L Body temp25.4 L  NB. a mole of volatile liquid (e.g gm Halothane) 22.4 L vapour at STP  PV=RT R (molar gas constant) = 1 x 22.4 / 273=0.082 litre.atm /degree o A/ mole =1.987 joule / degree / mole (S.I)  A mole of any gas contains the same number of molecules = 6.02 x ………… ……………….” Avogadro’s number” Amadeo Avogadro ( ) Italy

John Dalton DALTON’S law of Partial Pressure “ the pressure exerted by a mixture of gases (and/ or vapours) – enclosed in a given space – is equal to the sum of pressures which each gas (or vapour) would exert if it alone occupied the same space” Partial Pressure (P.P) = total pressure x volume % Volume % = (P.P / total P ) x 100

Saturated Vapor Pressure (SVP) varies as a function of: nature of liquid its temperature mmHg (20 o C) -Desflurane 670 -Diethyl ether 440 -Halothane 243 -Isoflurane239 -Enflurane175 -Sevoflurane 160 -Trilene 60 -Methoxyflurane23

Summary of important points Basic S.I units - length = Meter m - mass = Kilogram Kg - time = Second s - electric current = Ampere A - temperature = Kelvin o K - amount of substance = Mole mol - luminous intensity = Candela cd Derived units - area =m 2 - volume = m 3 - velocity =ms -1 - acceleration = ms -2 - force =Kgms -2 = Newton N - work (energy) = Kgm 2 s -2 = Nm = Joule J - power = Kgm 2 s -3 = Js -1 = Watt W

- pressure = Nm -2 = Pascal Pa - frequency = Hertz Hz - electric charge = Coulomb C - potential difference (EMF) =Volt V - electric resistance = Ohm Ω - electric capacitance = Farad F - magnetic flux = Weber Wb VAPOUR is the gaseous state of the substance which is present in the liquid form at RTP GAS is a substance which cannot exist in the liquid form at RTP

Boyle’s law : V  1/P at constant temperature Charles' law : V  T ( o A) at constant pressure Gay-Lussac’s law : P  T at constant volume Critical Temperature : “ the temperature above which a gas cannot be liquefied whatever pressure is applied ” Avogadro’s hypothesis : “EQUAL volumes of perfect gases at same temperature and pressure contain same number of molecules” Avogadro’s number : A mole of any gas contains the same number of molecules = 6.02 x DALTON’S law of Partial Pressure Partial Pressure (P.P) = total pressure x volume %

Examples of questions to assess the ILOs 1.Which of the following units are BASIC SI units of measurement? a)Kilometre. b)Candela. c)Watt. d)Kilogram.

2.The following are correct S.I. Units a)The unit of energy is the Newton b)The unit of power is the Watt c)The unit of frequency is the Hertz d)The unit of mass is the gram a)The unit of length is the metre

3.The critical temperature is: a) 273 K b) the temperature above which a gas cannot be liquified by pressure alone c) the temperature below which a gas does not vaporise d) 36.5 degrees C for nitrous oxide e) different if a substance is in a mixture rather than on its own

4.Concerning the gas laws a)Boyle's law refers to the relationship between temperature and pressure of a gas b)Temperature is measured on the absolute temperature scale c)Temperature is a constant in Charles' law d)Boyle's law states that at a constant volume pressure varies with temperature e)The gas laws are only true for air

5.One mole of a gas a)Occupies 22.4 Litres at room temperature b)Has the same volume for any gas c)Contains Avogadro's number of molecules d)May be liquefied by compression if above critical temperature e)Is one gram molecular weight

Answers 1.false, true, false, true 2.false, true,true, false, true 3.false, true, false, true, true 4.false, true, false, false, false 5.false, true, true, false, true

Thank You