Science

Science

Physics

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 moleculesAmount 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 motionDirectly 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 = E C + 273 E C = K – 273

You choose fractions or decimals: E C = ( E F – 32) / 1.8 OR E C = ( E F - 32) • 5/9 E F = ( E C • 1.8 )+ 32 OR E F = ( E 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 caloriesExample: 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 flowLaminar TurbulentTransitional

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/in²Your 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 mmHgDenver 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/Hg1 ATM14.7 lb/in²33.9 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:

GangreneDecompression 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!

Gas Laws

Boyle’s Law Charles's Law Gay Lussac’s Law Combined Gas Law

Boyle’s Law

What is constant? MASS & TEMP

What varies? PRESSURE & VOLUME

How do you think they vary? As pressure increases what happens to volume?

It decreases! So they are inversely related! ↑P = ↓V or ↓P = ↑V

Example

1st reading1 ATM3 L

2nd reading2 ATM unknown

Another Example

1st reading760 torr600 mL

2nd reading640 torr unknown

Charles’s Law

What is constant? MASS & PRESSURE

What varies? TEMP & VOLUME

How do you think they vary? As temp increases what happens to volume?

It increases! So they are directly related! ↑T = ↑ V or ↓T = ↓V

Example

1st reading585 mL19 °C

2nd reading42 °C unknown

Another Example

1st reading5 L250 K

2nd reading180 K unknown

Gay-Lussac’s Law

What is constant? MASS & VOLUME

What varies? TEMP & PRESSURE

How do you think they vary? As temp increases what happens to pressure?

It increases! So they are directly related! ↑T = ↑ P or ↓T = ↓P

Example

10 L of He has a pressure of 640 torr @ 295 K. What will the pressure be @ 317K?

P1 = 640 torr P2 = Unknown T1 = 295 K T2 = 317 k

Another Example

1st reading400 torr100 K

2nd reading300 torr unknown

Combined Gas Law

What is constant? JUST MASS

What varies? TEMP, VOLUME & PRESSURE When would we use the combined gas

law?

Example

3L of Oxygen at 1.5 ATMs with a temp of 200K is heated to 215 K at 10 ATMs. What is the new volume?

P1 = 1.5 ATMs V1 = 3 L T1 = 200 K P2 = 10 ATMs V2 = unknown T2 = 215 K

Diffusion

Diffusion means the slow steady movement of individual molecules from one region to another.

As solid as a pane of glass can seem, molecules of air can easily diffuse, or pass through the glass. This can readily be noticed on a cold winter night.

Diffusion

When diffusion takes place gas molecules move from an area of high partial pressure to an area of low partial pressure.

When gas diffusion takes place in the lungs, oxygen and carbon dioxide must move through significant barriers. Lung tissue Capillary wall Plasma Membrane of the RBC

Diffusion Laws

Fick’s Law Graham’s Law Henry’s Law

Fick’s Law

Diffusion = A X D X ∆P

T

A = Cross-Sectional Area

D = Diffusion Coefficient of a gas

∆P= Pressure Gradient of gas

T = Lung membrane thickness

Graham’s Law

Diffusion Coefficient = Solubility Coefficient (α) √¯gmw

Solubility Coefficient (α)= lab value given to every gas O2 = .023

CO2 = .51

Let’s compute the Diffusion Coefficient of O2 & CO2!

Henry’s Law

Henry’s law predicts how much of a given gas will dissolve in liquid.

Henry’s law states at a given temperature, the volume of a gas that dissolves in a liquid (V) is directly related to its solubility coefficient (α) multiplied by its partial pressure (Pgas).

V = α X Pgas

Example: the increased partial pressure of O2 in a hyperbaric chamber increases the oxygen diffusion into the blood and tissues.

Flow and Velocity

Flow is the movement of a volume of fluid per unit of time.L/secL/min

Velocity is a measure of linear distance traveled by the fluid per unit of time.

Bernoulli's principle

Provided driving pressure is constant, as gas flow meets a narrowing or restriction the molecules speed up with increasing forward velocity.

http://home.earthlink.net/~mmc1919/venturi.html

Bernoulli's principle

The increase in velocity is because the same number of molecules are trying to get through the narrowed opening in a given amount of time.

As a result, the molecules hit the sides of the tube less often, therefore there is a drop in lateral pressure. The molecules are spending more time going faster/forward and

less time hitting the walls of the tube. Egans p. 108 This drop in lateral pressure causes a vacuum or

sucking action that can be used to entrain (bring in) additional fluid.

Venturi Tubes & Mask

Venturi Tubes & Mask

The venturi tube is a modification of the Bernoulli's principle.

A venturi tube widens just after the jet port. This helps keep the FIO2 constant by restoring the

pressure and flow back toward the set values found before the narrowing.

The angle of widening has to be less than 15° to restore pressure an flow.

Egan p. 110

Venturi Tubes & Mask