1. Aim: What are the properties of Gases? DO NOW: Fill in the blanks. (increase or decrease for each blank) 1. As the volume of a gas ____________, the pressure ___________. 2. As the temperature on a gas _________, the pressure __________. 3. As the number of gas particles __________, the pressure __________. 4. As the temperature ___________, the volume of the gas___________.

2. Compressibility of Gases Compressibility is measure of how much volume decreases under increased pressure. Gases are easily compressed because of the space between the particles in a gas. The volume of the particles of the gas is small compared to the overall volume of the gas. Under increased pressure, the particles in a gas are forced closer together or compressed.

3. Factors Affecting Gas Pressure Four variables are used to describe a gas: 1. Pressure (P): kilo pascals 2. Volume (V): liters 3. Temperature (T): kelvin 4. Number of moles (n) The amount of gas, the volume, and the temperature are factors that affect gas pressure.

4. Amount of Gas By adding gas into a container, you increase the amount of collisions on the walls of the container, increasing the pressure If the container is rigid, the volume is constant and if the temperature is constant then the increase in pressure is proportional. If I double the number of particles, the pressure will double.

5. Volume You can increase pressure by decreasing volume The more a gas is compressed, the more pressure the gas exerts. By halving the volume, you double the pressure. By doubling the volume, the pressure is halved.

6. Temperature As temperature increases, pressure increases. Increasing average kinetic energy, increases the hits on the container wall and the amount of force on the wall which increases pressure. As temperature doubles, pressure doubles As temperature decreases, pressure decreases.

7. Part II: Gas Laws

8. Kinetic Molecular Theory (KMT) Kinetic molecular theory (KMT) for an ideal gas states that all gas particles: are in random, constant, straight-line motion. are separated by great distances relative to their size; the volume of the gas particles is considered negligible. have no attractive forces between them. have collisions that may result in a transfer of energy between gas particles, but the total energy of the system remains constant.

9. Boyle’s Law: Pressure-Volume Relationship The volume of a fixed mass of gas varies inversely with the pressure at constant temperature. As the volume increases the pressure decreases. As the volume decreases the pressure increases. P 1 V 1 = P 2 V 2 P 1 = initial pressureP 2 = final pressure V 1 = initial volumeV 2 = final volume

11. Practice – solve the following using Boyle’s law 1) A 4L balloon at 1 atm is released and the volume expands to 6L. Find the new pressure. 2) A 4L balloon at 101.3 kPa is placed under pressure of 202.6 kPa. Find the new volume.

12. Summary Explain in terms of collision why decreasing the volume of a gas increases the gas pressure.

13. Aim: How does a change in temperature affect volume and pressure of a gas? DO NOW: In pairs answering the following questions using Boyle’s Law. 1.A balloon contains 7.2 L of He. The pressure is reduced to 2.00 atm and the balloon expands to occupy a volume of 25.1 L. What was the initial pressure exerted on the balloon? 2.A sample of neon occupies a volume of 461 mL at STP (standard pressure is 101.3 kPa). What will be the volume of the neon when the pressure is reduced to 93.3 kPa?

14. Charle’s Law: Volume- Temperature Relationship

16. Practice – solve the following using Charles’s law 1) A 2L balloon at 300 K is heated to 750 K. Find the new volume. 2) A 4L balloon at 100°C deflates to 2L. Find the new temperature.

17. Now try in pairs! 3.Calculate the decrease in temperature when 2.00 L at 20.0 °C is compressed to 1.00 L.

18. Gay Lussac’s Law: Pressure- Temperature Relationship

20. Practice – solve the following using Gay-Lussac’s law 1) A gas at 202.6 kPa and 300 K is heated to 400 K. Find the new pressure. 2) A gas at STP (standard pressure is 1 atm) is placed under a pressure of 3 atm. Find the new temperature.

21. Now try in pairs! 3. Determine the pressure change when a constant volume of gas at 1.00 atm is heated from 20.0 °C to 30.0 °C. (Make sure you change Celsius to Kelvin)

22. Exit Slip. On a separate sheet of paper to be collected answer the following question: How does a change in temperature affect volume and pressure of a gas?

23. Aim: How do you do calculations using the combined gas law? DO NOW: Take out your homework. In pairs discuss your responses.

24. Review of Boyle’s Law, Charles’ Law and Gay-Lussac’s Law

25. Combined Gas Law

26. Practice – solve the following using the combined gas law 1) A 3L canister of gas is at 1.5 atm and 200 K. It is heated to 400 K causing the volume to increase to 7L. What is the new pressure? 2) A 1.5L balloon at STP is placed under pressure of 148.4 kPa and temperature is lowered to 200 K. Find the new volume.

27. Now you try in Pairs! 3. What is the volume at STP of 720.0 mL of a gas collected at 20.0 o C and 3.00 atm?

28. Aim: How is an ideal gas different than a real gas? DO NOW: Take out your homework. In pairs discuss your answers to the homework.

29. Review KMT Kinetic molecular theory (KMT) for an ideal gas states that all gas particles: are in random, constant, straight-line motion. are separated by great distances relative to their size; the volume of the gas particles is considered negligible. have no attractive forces between them. have collisions that may result in a transfer of energy between gas particles, but the total energy of the system remains constant.

30. Deviations of Real Gases from Ideal Behavior A real gas: ◦Does not behave completely according to the KMT. ◦Occupies space and exert attractive forces between on one another

31. Ideal Gas vs. Real Gas LIKELY TO BEHAVE IDEAL Gases at high temperature and low pressure. Small nonpolar gas particle. LIKELY TO NOT BEHAVE IDEAL Gases at low temperature and high pressure. Large polar gas molecules.

32. Practice Questions 1. A real gas behaves more like an ideal gas when the gas molecules are a. close an have strong attractive forces between them b. close and have weak attractive forces between them c. far apart and have strong attractive forces between them d. far apart and have weak attractive forces between them

33. Practice Questions cont. 2. Under which conditions of temperature and pressure would gaseous molecules most likely be closest together? a. high pressure and low temperature b. high pressure and high temperature c. low pressure and high temperature d. low pressure and low temperature