1 / 24

The Kinetic Theory of Gases

Physics 12. The Kinetic Theory of Gases. Objectives. Define pressure . State the assumptions of the kinetic model of an ideal gas. State that temperature is a measure of the average random kinetic energy of the molecules of an ideal gas.

jarrod-eaton
Download Presentation

The Kinetic Theory of Gases

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physics 12 The Kinetic Theory of Gases

  2. Objectives • Define pressure. • State the assumptions of the kinetic model of an ideal gas. • State that temperature is a measure of the average random kinetic energy of the molecules of an ideal gas. • Explain the macroscopic behavior of an ideal gas in terms of a molecular model. • State the equation of state for an ideal gas. • Describe the difference between an ideal gas and a real gas. • Describe the concept of the absolute zero temperature and the Kelvin scale of temperature • Solve problems using the equation of state of an ideal gas.

  3. Activities • Lecture • Quiz • Computer simulation • Graphical analysis

  4. Gases • Compared to solids and liquids, gases behave quite differently, particularly in the volume that they occupy. • What are some factors that might affect the volume that a gas occupies? • Explain this behavior from a microscopic perspective.

  5. Gases • How would these factors affect the volume of a gas?

  6. Gases • Because of the myriad of factors that affect the behavior of gases, it is valuable to determine a relationship between them. • The relationship between the volume, pressure, temperature, and mass of a gas is called an equation of state. • By state, we mean the equilibrium state of the system.

  7. Gases SI units for quantities involving gases **another unit for pressure, the atmosphere (atm) is often used: 1 atm = 1.01 x 10 5 Nm-2

  8. Boyle’s law • What is the effect of pressure on the volume of a gas?

  9. Boyle’s law • For a given quantity of gas, it is found experimentally that the volume of a gas is inversely proportional to the absolute pressure applied to it when the temperature is kept constant. V α 1/P • Why is it important that we state that temperature is constant?

  10. Boyle’s law Graph of P vs. V (Boyle’s experiments) • What are the implications of this relationship on the behavior of gases?

  11. Charles’s law • A century later, Jacques Charles performed experiments on the effect of temperature on gases. • What is the effect of temperature on the volume of a gas?

  12. Charles’s law • The volume of a given amount of gas is directly proportional to the absolute temperature when the pressure is kept constant. V α T • Can you think of any applications / examples of this in the “real world”?

  13. Absolute zero • Recall the relationship between the Kelvin and Celsius scales. • What kind of relationship is this?

  14. Gay-Lussac’s law • What is the effect of temperature on pressure?

  15. Gay-Lussac’s law • At constant volume, the absolute pressure of a gas is directly proportional to the absolute temperature.

  16. The ideal gas law • The three laws can be combined into ONE general relationship between the three variables: PV α T • There is one more factor that might affect pressure or volume that is not present; what is it?

  17. The ideal gas law • The amount of gas should also affect its volume: PV α mT • The amount of matter is expressed in moles. • 1 mol of a substance contains 6.02 x 1023 atoms or molecules of the substance (Avogadro’s number). • Why don’t we use kilograms to express the amount of matter?

  18. The ideal gas law • But an expression of proportionality is not nearly as useful as an equation, which brings us to the ideal gas law: PV = nRT Where: P is the pressure of the gas, V is the volume, n is the number of moles, and T is the temperature of the gas. R is the universal gas constant (the constant of proportionality between all four factors: R = 8.314 Jmol-1K-1

  19. The ideal gas law Determine the volume of 1.00 mol of any gas at STP (standard temperature, 0C, and pressure, 1.00 atm).

  20. The ideal gas law V = 22.4 L at STP

  21. The ideal gas law A helium party balloon, assumed to be a perfect sphere, has a radius of 18.0 cm. At room temperature (20C), its internal pressure is 1.05 atm. Find the number of moles of helium in the balloon and the mass of the helium needed to inflate the balloon to these values. The atomic mass of helium is 4.00 gmol-1

  22. The ideal gas law n = 1.066 mol m = 4.26 g

  23. Objectives • Define pressure. • State the assumptions of the kinetic model of an ideal gas. • State that temperature is a measure of the average random kinetic energy of the molecules of an ideal gas. • Explain the macroscopic behavior of an ideal gas in terms of a molecular model. • State the equation of state for an ideal gas. • Describe the difference between an ideal gas and a real gas. • Describe the concept of the absolute zero temperature and the Kelvin scale of temperature • Solve problems using the equation of state of an ideal gas.

  24. Homework Giancoli pg 381 # 29, 31, 33, 35, 39 Quiz next class on gas laws Next lectures: Chapter 15-1 to 15-3

More Related