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Applied Physics

Applied Physics. RET 2274 Respiratory Therapy Theory I Module 1.0. States of Matter. Three Primary States of Matter. Solid. Liquid. Gas. States of Matter. Solid Atoms are kept in place by strong mutual attractive forces and are limited to back-and-forth motion about a central position.

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Applied Physics

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  1. Applied Physics RET 2274 Respiratory Therapy Theory I Module 1.0

  2. States of Matter • Three Primary States of Matter Solid Liquid Gas

  3. States of Matter • Solid • Atoms are kept in place by strong mutual attractive forces and are limited to back-and-forth motion about a central position

  4. States of Matter • Liquid • Atoms are kept in place by mutual attraction (much weaker than that of solids) and can move about freely and can take the shape of their container – capable of flow. Like solids, liquids are dense and cannot easily be compressed

  5. States of Matter • Gas • Molecular attractive forces are very weak and their movement is rapid and random with frequent collisions. Gases have no inherent boundaries and are easily compressed and expanded. Like liquids, gases can flow. Liquids and gases are considered fluids.

  6. Temperature Scales • Absolute Zero • The concept that a temperature exists at which there is no kinetic energy (energy of motion) – exists in theory only • Kelvin (K) • Zero degrees K = absolute zero • Freezing point of water = 273 K • Boling point of water = 373 K

  7. Temperature Scales • Celsius (C) • Freezing point of water = 0º C • Boiling point of water = 100º C • Note: To covert degrees Celsius to degrees Kelvin, simply add 273 Example: 25º C = 25 + 273 = 298º K

  8. Temperature Scales • Fahrenheit • Freezing point of water = 32º F • Boiling point of water = 212º F • To covert degrees Fahrenheit to degrees Celsius, use the following formula ºC = 5/9 (ºF – 32) • To covert degrees Celsius to degrees Fahrenheit, use the following formula ºF = (9/5 x ºC) + 32

  9. Temperature Scales • Linear relationship between gas molecular activity, or pressure, and temperature. The graph shows comparable readings on three scales for five temperature points Freezing point of water Boiling point of water

  10. Change of State • Liquid-Solid Phase Changes • The changeover from the solid to liquid state is calledMELTING • The temperature at which solid change to liquid is called the MELTING POINT

  11. Change of State • Liquid-Solid Phase Changes • The changeover from the liquid to solid state is calledFREEZING; it is the opposite of melting • The FEEZING POINTS and MELTING POINTS of a substance are the same

  12. Change of State • Liquid-Vapor Phase Changes • As the temperature of a liquid increases, its state changes to VAPOR

  13. Change of State • Liquid-Vapor Phase Changes • This change of state is called VAPORIZATION • Two different forms of vaporization BBOILING EVAPORATION

  14. Change of State • Liquid-Vapor Phase Changes • Boiling occurs at the BOILING POINT • The boiling point of a liquid is the temperature at which its vapor pressure equals atmospheric pressure – its molecules must have enough kinetic energy to force themselves into the atmosphere against the opposing pressure

  15. Change of State • Liquid-Vapor Phase Changes • Boiling occurs at the BOILING POINT • The boiling point of liquid oxygen at 1 atmosphere pressure is -183º C

  16. Change of State • Liquid-Vapor Phase Changes • EVAPORATION is when a liquid changes into a gas at temperatures lower than its boiling point • After water is converted to a vapor, it acts like any gas. This invisible gaseous form of water is called MOLECULAR WATER

  17. Change of State • Liquid-Vapor Phase Changes • When a gas is fully saturated with water vapor, slight cooling of the gas causes its water vapor to turn back into the liquid state, a process called CONDENSATION • The temperature at which condensation begins is called the DEW POINT

  18. Changes of State • Critical Temperature • The highest temperature at which a substance can exist as a liquid • Critical Pressure • The pressure needed to maintain equilibrium between the liquid and gas phases of a substance at its critical temperature A typical phase diagram. The dotted green line gives the anomalous behavior of water

  19. Phase Diagram

  20. Properties of Liquids • Pressure in Liquids • Liquids exert pressure • The pressure exerted by a liquid depends on both its height (depth) and weight density (weight per unit volume) Pascal’s principle. Liquid pressure depends only on the height (h) and not on the shape of the vessel or the total volume of liquid. (Modified from Nave CR, Nave BC: Physics for the health sciences, ed 3, Philadelphia, 1985, WB Saunders.)

  21. Properties of Liquids • Buoyancy • Liquids exert buoyant force because the pressure below a submerged object always exceeds the pressure above it. • The upward buoyant force will overcome gravity, and the object will float

  22. Properties of Liquids • Buoyancy • Gases also exert buoyant force, which helps keep solid particles suspended in gases Blue and white smoke ascending

  23. Properties of Liquids • Viscosity • Viscosity is the force opposing a fluid’s flow; viscosity in fluids is like friction in solids • A fluids viscosity is directly proportional to the cohesive forces between it molecules; the stronger the cohesive forces, the greater is the fluid’s viscosity

  24. Properties of Liquids • Viscosity • The greater a fluid’s viscosity, the greater is its resistance to deformation and the greater is its opposition to flow

  25. Properties of Liquids • Viscosity • The greater the viscosity of a fluid, the more energy is needed to make it flow • Example: When there is an increase in red blood cells (polycythemia), the heart must work harder to circulate the blood because it is more viscous

  26. Properties of Liquids Laminar Flow When fluids move in discrete cylindrical layers called streamlines

  27. Properties of Liquids Laminar Flow The difference in the velocity among these concentric layers is called shear rate The pressure pushing or driving the fluid is called shear stress

  28. Properties of Liquids • Cohesion and Adhesion • The attractive force between like molecules is called cohesion

  29. Properties of Liquids • Cohesion and Adhesion • The attractive forces between unlike molecule is adhesion

  30. Properties of Liquids • Cohesion and Adhesion • The shape of the meniscus depends on the relative strengths of adhesion and cohesion. A, Water; adhesion stronger than cohesion. B, Mercury; cohesion stronger than adhesion

  31. Properties of Liquids • Surface Tension • The force exerted by like molecules at a liquid’s surface

  32. Properties of Liquids • Surface Tension • The force of surface tension in a drop of liquid. Cohesive force (arrows) attracts molecules inside the drop to one another. Cohesion can pull the outermost molecules inward only, creating a centrally directed force that tends to contract the liquid into a sphere

  33. Properties of Liquids • Surface Tension • The lungs resemble clumps of bubble, it follows therefore that surface tension plays a key role in the mechanics of ventilation • Abnormalities in alveolar surface tension occur in certain clinic conditions, e.g., infant respiratory distress syndrome

  34. Properties of Liquids • Surface Tension • Laplace’s Law: In a liquid sphere, the pressure required to distend the sphere is directly proportional to the surface tension of the liquid and inversely proportional to the sphere’s radius

  35. Properties of Liquids • Surface Tension Laplace’s relationship. Two bubbles of different sizes with the same surface tension. Bubble A, with the smaller radius, has the greater inward or deflating pressure and is more prone to collapse than the larger bubble B. Because the two bubbles are connected, bubble A would tend to deflate and empty into bubble B. Conversely, because of bubble A’s greater surface tension, it would be harder to inflate than bubble B. Equation for liquid bubble P = 4ST r P = distending pressure ST = surface tension r = spherical radius

  36. Properties of Gases • Gases share many properties with liquids • Gases: • Exert pressure • Capable of flow • Exhibit the properties of viscosity However, unlike liquids, gases are readily compressed and expanded and fill the spaces available to them through diffusion

  37. Properties of Gases • Gaseous Diffusion • Diffusion:The process whereby molecules move from areas of high concentration to areas of lower concentration • Kinetic Energy: The driving forced behind diffusion. Because gases have high kinetic energy, they diffuse most rapidly Note: Because diffusion is based on kinetic activity, anything that increases molecular activity will quicken diffusion, e.g., heating

  38. Properties of Gases • Gaseous Diffusion • Graham’s Law: The rate of diffusion of a gas (D) is inversely proportional to the square root of its density: Lighter gases diffuse rapidly, whereas heavy gases diffuse more slowly

  39. Properties of Gases • Gas Pressure • Whether free in the atmosphere, enclosed in a container, or dissolved in a liquid such as blood, all gases exert pressure • In physiology, the term tension is often used to refer to the pressure exerted by gases when dissolved in liquids • Pressure is a measure of force per unit area • PSI: Pounds per square inch (lb/in²) • British fps • N/m² : Newton per meter squared (Pascal) • International System of Units (SI)

  40. Properties of Gases • Gas Pressure • Pressure can also be measured indirectly as the height of column of liquid: Centimeters of water pressure (cm H2O) Millimeters of mercury (mm Hg) • Both mercury and water columns are still used in clinical practice, especially when vascular pressures are being measured

  41. Properties of Gases • Partial Pressure (Dalton’s Law) • Many gases exist together as mixtures, for example air, which contain mostly oxygen and nitrogen • The pressure exerted by a single gas is called its partial pressure PressureTotal = Pressure1 + Pressure2 ... Pressuren

  42. Properties of Gases • Partial Pressure (Dalton’s Law Partial Pressure = Fractional concentration x Total atmospheric pressure

  43. Properties of Gases Composition of Earth’s Atmosphere

  44. Properties of Gases • Solubility of Gas in Liquids (Henry’s Law) • At a constant temperature, the solubility of a gas in a liquid is proportional to the pressure of that gas above the liquid William Henry (chemist)

  45. Properties of Gases • Solubility of Gas in Liquids (Henry’s Law) • Temperature plays an important role in gas solubility • High temperatures decrease solubility • Low temperatures increase solubility Leave a carbonated drink open and out of the refrigerator and it will quickly go flat

  46. Gas Laws Several laws help define the relationship among gas pressure, temperature, mass, and volume Boyle’s Law Charles’ Law Gay-Lussac’s Law Combined Gas Law

  47. Gas Laws Boyle’s Law

  48. Gas Laws Boyle’s Law

  49. Gas Laws Charles’ Law

  50. Gas Laws Charles’ Law

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