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Gas class #1

Gas class #1. OBJECTIVE: understanding the nature of gases, the KMT, the 4 variables to measure gases, and the first demo diagram for gases.

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Gas class #1

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  1. Gas class #1 OBJECTIVE: understanding the nature of gases, the KMT, the 4 variables to measure gases, and the first demo diagram for gases.

  2. During phases we covered gases a bit, but now we will truly examine them in more detail. The Kinetic Molecular Theory (KMT) explains them generally, and we need to be familiar with that. For review… • The Kinetic Molecular Theory to explain gases • Gases are made up of hard spherical particles called atoms or molecules • Gas particle volume is very small to the size the gas takes up • The gas particles have no attraction or repulsion for each other.

  3. During phases we covered gases a bit, but now we will truly examine them in more detail. The Kinetic Molecular Theory (KMT) explains them generally, and we need to be familiar with that. For review… • The Kinetic Molecular Theory to explain gases • Gases are made up of hard spherical particles called atoms or moleculesthese particles are hardly ever “round or spherical” but they do act that way. • Gas particle volume is very small to the size the gas takes upgases can be compressed greatly (more than 200x), the particle volume is considered to be insignificant compared to the size the gas takes up • The gas particles have no attraction or repulsion for each other.This is not really true, but with the energy provided by the Universe (Sun and Earth’s heat) this is overcome readily, gases usually remain gases

  4. The Kinetic Molecular Theory to explain gases 4 Particles of a gas move rapidly and only in straight lines 5 Particle collisions are elastic – no loss of energy by bumping 6 The average kinetic energy of a gas is directly proportional to the temperature of the gas in Kelvin 7 The collisions of the particles of gas result in pressure being created

  5. The Kinetic Molecular Theory to explain gases 4 Particles of a gas move rapidly and only in straight linesnone of the gas atoms or molecules moves in a curve. 5 Particle collisions are elastic – no loss of energy by bumping of course gas particle collisions create heat and have energy loss, but it’s so small compared to the energy they gain from the Universe, it seems that gases just remain gases, never running out of energy 6 The average kinetic energy of a gas is directly proportional to the temperature of the gas in KelvinThe more energy the gas has, the hotter the gas is (that applies to all phases)the hotter the gas, the more KE the particles have 7 The collisions of the particles of gas result in pressure being createdThe more collisions, the greater the pressure; the stronger the collisions, the greater the pressure.

  6. The 4 variables to measure gases… • The pressure of a gas, using any units you know such as: kilo-Pascals kPa atmospheres atm millimeters of mercury mm Hg pounds per square inch psi • The temperature of a gas, using only KELVINZero temperature means zero on only one scale. Normally chilly temperatures around here of 0°C or -5.5°C will create math problems with our formulas. Only Kelvin, OK (not absolute zero either!) • The volume of a gas, using any units you know, probably though it will be in Liters, or milliliters. • The number of moles of gas, (they’re back!)

  7. Kinetic Energy and Temperature are DIRECTLY PROPORTIONAL Which means, as one goes up, so does the other. If one variable here goes, down, so does the other. The line must be straight, the slope constant, but it does not have to be a 1:1 ratio (45°angle). KineticEnergy Temperature in Kelvin

  8. Gas Demo Diagram #1 (loose paper, to be collected with the rest of the diagrams) Title: Relationship between the Volume and Temperature of Gases balloons water ice HEAT

  9. THINK, don’t write yet… COLD… the balloon in the cold water will change size what size will it get? Bigger or smaller? HOT… the balloon in the hot water will change size too. Will it get bigger or smaller?

  10. Cold will make the balloon shrink, why? The colder the gas particles, the lower their kinetic energy, the weaker the collisions and the fewer collisions will occur. Lower temperature reduces volume. Hot will make the balloons expand, why? The hotter the gas particles, the greater their kinetic energy, the stronger the collisions and the more collisions will occur. Higher temperature increases volume.

  11. Volume and Temperature of a gas are DIRECTLY PROPORTIONAL Hotter temps mean bigger balloons. Lower temps mean smaller balloons. Temp as a Function of Volume Volume as a Function of Temp temp Volume volume temp

  12. Back to Notes… Draw three small graphs… Annual Income as a function of years of college; test scores as a function of hours studying; and, heart rate as a function of running speed. (X as a Function of Y each time!)

  13. Each of those graphs is directly proportional. Not necessarily a 1:1 ratio, but as one variable increases, so does the other. With gases, Volume and Temperature are directly proportional. Tonight… Gas HW #1 to be collected tomorrow.

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