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What is Physics? • The study of the laws of matter and their interaction with energy.
What are the 3 states of matter? • Solid • Liquid • Gas
Solids • Rigid & elastic • High degree of internal order • The atoms found in solids are fixed & maintain their shape due to strong mutual attractive forces, which are called van der waals forces • Can not be compressed • The atoms found in solids are limited to back and forth motion in a central location
Liquids • Flow to fill the bottom of a container • Liquids have weaker van der waals than solids but stronger van der waals than gases • The atoms can move around freely & therefore maintain the shape of their container • Not easily compressed
What is a fluid? • Anything that flows!!!!! • LIQUIDS AND GASES!
Gases • They have to be contained, they inhibit NO boundaries! • Easily compressed • The atoms in gases have very weak van der waals, therefore these atoms have rapid & random motion with frequent collisions • All gases exert a pressure
Pressure • Def: The force exerted over a given area • Factors that affect gas pressure • Number of molecules • Amount of collisions • between the molecules • between the molecules and the sides of the container • DIRECTLY RELATED TO TEMPERATURE!
The First Law of Thermodynamics • States that energy can never be lost nor created, it is only transformed!
2 kinds of Internal Energy • Potential (mass x gravity x height) • Energy of position • Kinetic (½ x mass x speed²) • Energy of motion • Directly related to temperature
States of Matter & Internal energy • Solid • Highest potential energy • Lowest kinetic energy • Liquid • Higher potential than kinetic • Gas • Lowest potential energy • Highest kinetic energy
Temperature Scales • Fahrenheit • °F • Non-metric • Melting & boiling points are whole numbers • Celsius • °C • Metric & centigrade • 100 degrees between freezing & boiling points • Kelvin • K • An extension of Celsius, scaled down to ABSOLUTE ZERO! • 100 degrees between freezing & boiling points
ABSOLUTE ZERO • In concept, absolute zero is a temperature in which all kinetic energy is stopped. • It is a theoretical value, meaning it has never been reached! • 0 K • -273 °C • -460 °F
Converting between the 3 temperature scales • The easy one: • K = ̊ C + 273 • ̊ C = K – 273 • You choose fractions or decimals: • ̊ C = ( ̊ F – 32) / 1.8 OR ̊ C = ( ̊ F - 32) • 5/9 • ̊ F = ( ̊ C • 1.8 )+ 32 OR ̊ F = ( ̊ C • 9/5 )+ 32
Heat transfer • Transfer of internal energy from a high temperature object of matter to a lower temperature object of matter. • Based on the 1st Law of Thermodynamics.
Heat transfer • Conduction • Convection • Radiation • Vaporization
Conduction • The transfer of heat through direct contact. • How well it transfers depends on the number & force of molecular collisions between objects. • This is the chosen route of heat transfer for solids. • Metals have the highest conductivity and gases have the lowest. • Example: placing your hand on a hot surface
Convection • The transfer of heat through the mixing of molecules at different temperatures. • This is the chosen route of heat transfer for fluids. • Convection currents = Fluid movements that carry heat. • Examples: convection oven & heating a house with a furnace
Radiation • The transfer of heat through indirect contact. • Radiation uses infrared light to heat objects. • Infrared light is light beyond the visible range. The color of light is determined by the frequency of its waves. Infrared light has lower frequency than visible light. • Example: sun warming earth & radiant warmers
Vaporization • The transfer of heat through a change of state from a liquid to a gas & vice versus. • Evaporation = consist of a change of state from a liquid to a gas. • Requires heat • Usually evaporation changes state via the boiling point • Example: boiling water & sweating • Condensation = consist of a change of state from a gas to a liquid. • Gives off heat • Example: the condensation of breath on a car window in cold temp.
Change of State • All matter can change state. • Solid to Liquid changes • When heating a solid, it’s kinetic energy increases. This increases the molecular vibrations, which will weaken the attractive forces. The molecules will eventually break free and form a liquid. • The temperature that constitutes the change from a solid to a liquid is called the melting point.
Change of State • Latent heat = is the general term for the energy required or produced in a change of state. • Measured in calories • Example: condensation gives off latent heat
Change of State • Liquid to Solid changes • When cooling a liquid, it’s kinetic energy slows down. This decreases the molecular vibrations, which will strengthen the attractive forces. The molecules will eventually become more stable and form a solid. • During the freezing of liquids the heat (energy) produced is usually transferred to the environment. • The temperature that constitutes the change from a liquid to a solid is called the freezing point.
Change of State • The amount of energy required to freeze a substance must equal the amount of energy required to melt it. • So this means the melting and freezing points have to be the same temperature.
Mass, Weight, & Density • Mass = The measure of the inertia possessed by an object. • Inertia = property of matter which causes matter to resist change. • Weight = is a force on an object that results from the earth’s pull of gravity. • Density = ratio of the mass/weight of a substance to it’s volume.
Mr. Avogadro • What is Avogadro's #? • Avogadro's Law says that 1 gram of any substance contains exactly the same # of atoms (6.02 X 10²³). • Avogadro's number of hydrogen atoms has a mass of 1 gram and equals 1 mole of hydrogen. • Avogadro made up the unit mole because it was easier to document. • Also, 1 mole which is 1 gram and 6.02 X 10²³ molecules takes up 22.4L of volume. • How many molecules are there in 2 moles of hydrogen? • 12.04 X 10²³ molecules
Fluid Density • The units of measurement of gas density are g/L • Your will divide the gram molecular weight (gmw) by the molar volume of the gas in liters. • Molar volume = equal volumes of gases under the same conditions must contain the same # of molecules per Mr. Avogadro. • I gmw = I mole of gas @ STPD = 22.4 L • Example: • What is the gmw of Oxygen (O²)? • What is the density of Oxygen?
Density of Air • Air is made up of more than one gas. • Consist of approximately 21% Oxygen and 79% Nitrogen. • First we have to get the gmw or air. • Do we just add 32g to 28g & divide by 22.4? • NO!
Density of Air • We have to take the appropriate percentage of Nitrogen and add it to the appropriate percentage of Oxygen. • .79(28) + .21(32) = X • 22.12 + 6.72 = 28.84 • Now we have to account for the molar volume. What do we do next? • 28.82 / 22.4 = X • The density of air is 1.29 g/L!
Patterns of Flow • The pattern of flow varies with the pressure gradients of the fluid. • Pressure gradient = The amount of pressure change occurring over a given distance. • A gradient of a fluid is the difference between the starting and finishing pressures in a confined tube.
Patterns of Flow • There are 3 patterns of flow • Laminar • Turbulent • Transitional
Laminar • Fluid moves in discrete cylindrical layers or streamlines • Usually found in a smooth tube • Poiseulle researched and determined that the laminar flow rate of a fluid along a pipe is proportional to the fourth power of the pipe's radius applied to pi. He also said flow rate is dependant upon fluid viscosity (η), pipe length (L), and the pressure difference between the ends (.P). • This equation is used to solve for unknowns. • Poiseulle’s Law
Turbulent • Fluid molecules form irregular currents in a chaotic pattern. • The change from laminar to turbulent depends on: • Density (d) • Viscosity (η) • Linear velocity (v) • Tube radius (r) • All of these factors give us Reynolds's Number!
Reynolds's Number • Equation can solve for unknowns: If Reynolds's number is greater than 2000 then flow is considered turbulent. If Reynolds's number is less than 2000 then flow is considered laminar.
Transitional • Fluid molecules that transition between laminar and turbulent flow. • Example: tracheobronchial tree
Viscosity of Fluids • Shear rate = difference in velocity among concentric layers. • It is a measure of how easily the layers separate • It is dependant on 2 things • Pressure pushing or driving the fluid (shear stress) • Viscosity of the fluid
Atmospheric Gases • The molecules in the atmosphere are colliding with each other and their container, which creates a pressure. • This is called barometric pressure • What 2 ways can we increase or decrease this pressure?
Barometric pressure • There is such a tremendous amount of air above us that explains why our atmosphere exerts an incredible amount of force (pressure). • 14.7 lb/in² • Your palm is approximately 20 in², that is 294lbs of force pushing down on your palm. • Why does it not crush under this force?
The Atmosphere • It is denser the closer to sea level you get. • Increased gravity = increased density • Increased altitude = decrased density • In Colorado we are far enough away from sea level to see a difference in the barometric pressure. • Sea level 760 mmHg • Denver 640 mmHg
Barometer • The tool used to measure the atmospheric pressure. • A long tube is filled with mercury & inverted into a pool of mercury. • The mercury sinks from the top of the tube and creates a vacuum. • At sea level the barometric pressure will push on the pool of mercury and cause the column to rise to approximately 76cm (hence Pb = 760mmHg).
The Atmosphere • The Atmosphere exerts a pressure at sea level of: • 760 mm/Hg • 1 ATM • 14.7 lb/in² • 33.9 ft/H2O • If 1 in = 2.54 cm, what is the pressure in cm/H2O?
Conversion Factors between common pressure units • cmH2O » mmHg = 0.7355 • mmHg » KPA = 0.133 • psi » KPA = 6.895 • psi » cmH2O = 70.31 • 1 torr = 1 mmHg
Dalton’s Law • States that atmospheric pressure equals the sum of the partial pressures of gases that make up the atmosphere. • How much of the pressure in the atmosphere is created by oxygen? • Po2 = .21 X 760 torr = 160 torr • How much of the pressure in the atmosphere is created by nitrogen? • Pn2 = .79 X 760 torr = 600 torr • How do you think humidity would effect the barometric pressure? • Example: Houston’s air has about 70% humidity & Denver’s air has about 30%.
Alveolar Air Equation • PAO2 = FiO2 (Pb – PH2O) – PaCO2 X 1.25 • PAO2 = partial pressure of oxygen in alveoli • Normal = approx. 100 torr • FiO2 = fractional concentration of oxygen • Normal = .21 • Pb = barometric pressure • Normal = 760 torr • PH2O = partial pressure of water vapor in the alveoli • Normal = 47 torr • PaCO2 = partial pressure of Carbon dioxide in artery • Normal = 35-45 torr
Hyperbaric/Hypobaric Conditions • Hyperbaric = pressure above atmospheric (sea level). • > 760 torr • Found below sea level • Examples: ocean diving & hyperbaric chamber • Hypobaric = pressure below atmospheric (sea level). • < 760 torr • Found above sea level • Examples: mountains & airplane
Hyperbaric Chamber • Abbreviated: HBO • Uses hyperoxygenation to treat: • Gangrene • Decompression sickness (Binz) • CO poisoning
Humidity • Absolute humidity = the actual amount or weight of water in the gas (air). • Relative humidity = percentage of the ratio of actual water content (weight) compared to it’s capacity at STPD. • RH% = (actual/capacity) X 100
Humidity • Body Humidity = percentage of the ratio of actual water content (weight) compared to it’s capacity at BTPS. • At BTPS the air can hold 43.8mg/L • BH% = (actual/43.8) X 100 • Humidity Deficit = represents the amount of water vapor your body must add to inspired gas to achieve 100% saturation @ 37°C. • HD = capacity – actual • Remember capacity in the body is 43.8
Gas Laws • Gas laws help define the relationship among pressure, volume, temperature, and mass • Regardless of chemical composition, all gases are similar in their behavior in response to changes in temperature and pressure • We uses gas laws to predict how gases will behave under changing conditions.
Gas Laws • Things to remember: • Mass is ALWAYS constant! • Meaning the mass of a gas will never change even with a change in temp, pressure or volume. • Temperature ALWAYS needs to be in Kelvin!