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Starter S-146

Starter S-146. List five properties of gases. The Behavior of Gases. Chapter 14. 14.1 Properties of Gases. Chapter 14. 14.1 Properties of Gases. Gases are easily squeezed into a smaller volume Compressibility – how much the volume decreases under pressure

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Starter S-146

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  1. Starter S-146 List five properties of gases.

  2. The Behavior of Gases Chapter 14

  3. 14.1 Properties of Gases Chapter 14

  4. 14.1 Properties of Gases Gases are easily squeezed into a smaller volume Compressibility – how much the volume decreases under pressure Air bags can absorb energy by compressing a gas

  5. 14.1 Properties of Gases Gases can be compressed because the actual particles take up very little of the volume

  6. 14.1 Properties of Gases Four variables are used to describe gases • Pressure (P) – force per unit area on the container • Volume (V) – in liters, how much space the gas take up • Temperature (T) – average kinetic energy • Number of Moles (n) – how much of the gas is present

  7. 14.2 The Gas Laws Chapter 14

  8. 14.2 The Gas Laws Robert Boyle Boyle’s Law – If temperature is kept constant, as pressure increases the volume decreases So if T is constant or

  9. 14.2 The Gas Laws Since the equation is equal to a constant This is used to compare values as long as the temperature and the number of moles remain constant

  10. 14.2 The Gas Laws Jacques Charles Charles’s Law – If pressure is kept constant, as temperature increases, volume also increases That is or

  11. 14.2 The Gas Laws Since the equation is equal to a constant This is used to compare values as long as the pressure and the number of moles remain constant Temperature must always be calculated in Kelvin in all gas calculations

  12. 14.2 The Gas Laws Joseph Gay-Lussac Gay-Lussac’s Law – If volume is constant, when the temperature increases, pressure increases That is or Simulation

  13. 14.2 The Gas Laws Since the equation is equal to a constant This is used to compare values as long as the volume and the number of moles remain constant Temperature is in Kelvin

  14. 14.2 The Gas Laws Combined Gas Law – all three relationships are combined into This equation can be used to solve relationships that involve any combination of these three variables Just remove any variable that does not change

  15. 14.2 The Gas Laws Example – a sample of oxygen gas at STP is heated to 50.0oC at a constant volume, what is the new pressure? What stays constant?

  16. 14.2 The Gas Laws Example – If 40.0 mL of nitrogen gas at 812mmHg and 75.0oC is cooled to -30.0oC and has the pressure reduced to 125mmHg, what is the new volume?

  17. 14.3 Ideal Gas Chapter 14

  18. 14.3 Ideal Gas Avogadro’s Law – if the temperature and pressure are held constant, an increase in gas particles (moles) will cause an increase in the volume This can be written as Simulation

  19. 14.3 Ideal Gas The ideal gas law combines all the laws into one equation R is a constant Usually written as

  20. 14.3 Ideal Gas A container has 2,240,000 L of methane gas (CH4) at a pressure of 1500 kPa and a temperature of 42oC. • How many moles of gas are in the container? • How many grams of gas are in the container?

  21. 14.3 Ideal Gas An ideal gas – is an imaginary gas that always follows the ideal gas law In a real gas • Particles take up volume • Force exist between particles So real gases deviate from the an ideal gas especially at • Low temperature • High pressure

  22. 14.4 Gases: Mixtures and Movements Chapter 14

  23. 14.4 Gases: Mixtures and Movements Dalton’s Law of Partial Pressure – in a mixture of gases, the total pressure is the sum of the partial pressures of the gases Since the temperatures and volumes must be the same for each gas All that matters is the number of moles of gas present

  24. 14.4 Gases: Mixtures and Movements Dalton’s Law of Partial Pressure – in a mixture of gases, the total pressure is the sum of the partial pressures of the gases Since the temperatures and volumes must be the same for each gas All that matters is the number of moles of gas present

  25. 14.4 Gases: Mixtures and Movements The total air pressure is the sum of the partial pressures of the different gases

  26. 14.4 Gases: Mixtures and Movements The minimum partial pressure of oxygen needed for a human is about 16kPa Partial pressures are written with a subscript This can be calculated using the ideal gas law

  27. 14.4 Gases: Mixtures and Movements Thomas Graham Diffusion – tendency of particles to move toward areas of lower concentration Effusion - is the process in which individual molecules flow through a hole without collisions between molecules Simulation

  28. 14.4 Gases: Mixtures and Movements Graham’s Law of Effusion – the rate of effusion of a gas is inversely proportional to the square root of the gas’s molar mass Can be written If two objects are at the same temperature they must have the same kinetic energy

  29. 14.4 Gases: Mixtures and Movements So a larger molecule must be moving slower

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