Physical Principles of Respiratory Care Egan Chapter 6

Physical Principles of Respiratory Care I. States of Matter II. Change of State III. Gas Behavior Under Changing Conditions IV. Fluid Dynamics

I. States of Matter A. Internal Energy of Matter B. Heat and the First Law of Thermodynamics C. Heat Transfer 1. Conduction 2. Convection 3. Radiation 4. Evaporation and Condensation D. Laws of Thermodynamics 1. Internal Energy and Temperature 2. Absolute Zero 3. Temperature Scales

I. States of Matter 4  Three primary states of matter:

I. States of Matter 5  Solids  Have high degree of internal order  Fixed volume and shape  Strong mutual attractive force between atoms  Molecules have the shortest distance to travel before collision  This motion referred to as a “jiggle”

I. States of Matter 6  Liquids  Have fixed volume, but adapt to shape of their container  Atoms exhibit less degree of mutual attraction compared w/ solids  Shape is determined by numerous internal & external forces  Gases  No fixed volume or shape; weak attractive forces  Gas molecules exhibit rapid, random motion w/ frequent collisions

A. Internal Energy of Matter 7  Energy matter possesses = internal energy  Atoms of all matter at ordinary temperatures are in constant motion  Two major types of internal energy:  Potential energy  Energy of position (attractive forces between molecules)  Weak in gas state  Makes up most of internal energy in solids & liquids  Kinetic energy  Energy of motion  Makes up most of gases internal energy  All matter has some kinetic energy  CFFC3F4&index=5&feature=plpp_video CFFC3F4&index=5&feature=plpp_video

B. Heat & the First Law of Thermodynamics 8  Thermodynamics can refer to 2 subjects:  Science studying the properties of matter at various temperatures  Kinetics, (speed) of reactions of matter at various temperatures  Energy can be neither created nor destroyed  Energy gain by substance = energy lost by surroundings

C. Heat Transfer 9  When two objects of different temperature coexist, heat will move from hotter to cooler object until both are equal  First Law of Thermodynamics  Heat Transfer can Occur by  Conduction  Convection  Radiation  Evaporation and Condensation

C. Heat Transfer 1. Conduction  The transfer of heat by direct contact between hot and cold molecules  Heat transfer in solids occurs mainly via conduction  Thermal Conductivity  Measure to quantify heat transfer between objects  Metals have high level

C. Heat Transfer 11 Solids, particularly metals have a high level of thermal conductivity. The high thermal conductivity of metal quickly draws heat away from the skin, creating a feeling of “cold.”

C. Heat Transfer 12  Convection currents 2. Convection is heat transfer through the mixing of fluid molecules at different temperatures (movement of the fluid)  Heat transfer in both liquids and gasses occurs mainly by convection

C. Heat Transfer 13  Radiant Warmer 3. Radiation  Radiant heat transfer occurs without direct physical contact

C. Heat Transfer Evaporation: The change of state from liquid to gas below boiling point  Condensation: The opposite of evaporation

D. Laws of Thermodynamics  Three physical principles describe how energy is handled & transferred: 1. Conservation of Energy  Energy cannot be created or destroyed 2. Thermodynamic Equilibrium  Given time all systems will achieve lowest possible energy state (entropy) 3. Impossibility of Achieving Absolute Zero  At absolute zero all processes cease & entropy is at minimum

D. Laws of Thermodynamics 1. Internal Energy and Temperature  The temperature of an object is a measurement of its internal kinetic energy  The higher the temperature, the faster the molecules that comprise the object are moving The molecules of boiling water move faster than molecules of water at room temperature because they have more kinetic energy!

D. Laws of Thermodynamics 2. Absolute Zero  Concept  Lowest possible temperature that can be achieved  Temperature = no kinetic energy  Molecules cease to vibrate; object has no measurable heat  Scientists have not actually achieved it

D. Laws of Thermodynamics Temperature Scales  Fahrenheit (F) & Celsius (C) scales based on property of water  0° C is freezing point of water  - 273° C = kinetic molecular activity stops = 0 K  Kelvin scale (K ) based on molecular motion  Used by SI (Systeme Internationale) units  Zero point = absolute zero

D. Laws of Thermodynamics Temperature Scales

D. Laws of Thermodynamics Temperature Scales  Conversions:  ° K = ° C  ° C = 5/9 (° F – 32)  ° F = 9/5 °C + 32

Internal Energy and Temperature 21  Practice! 1. Convert 25°C to K 2. Convert 0°C to K 3. Convert 100 K to °C 4. Convert 54 K to °C 5. Convert 37°C to °F 6. Convert 20°C to °F 7. Convert 75° F to °C 8. Convert 100° F to °C

Equipment Required  Vent with heated wire circuit attached.  Circuit with water traps