1. Chapter 10. States of Matter 10.1 Kinetic Molecular Theory and Gases

2. POINT > Define the Kinetic Molecular Theory (KMT) POINT > Describe 5 assumptions about an “ideal gas” POINT > Describe properties of gases in terms of KMT POINT > Identify conditions that cause real gases to deviate from “ideal” gas behavior

3. POINT > Define the Kinetic Molecular Theory (KMT) Literal interpretation: “theory of moving molecules” KMT explains the behavior of gases, liquids, solids and the transitions between these three states Today we will focus on gases

4. KMT description of gases is based on five assumptions about an “ideal gas” Ideal gases don’t exist, but most gases DO behave this way under most conditions The five assumptions are as follows: POINT > Identify the FIVE assumptions about an “ideal gas”

5. 1. Gases are composed of tiny particles far apart relative to their size: The volume occupied by the gas molecules is inconsequential The volume is mostly empty space

6. POINT > Identify the FIVE assumptions about an “ideal gas” 2. Gas particles are in continuous, rapid, random motion As a result, there are collisions with other molecules or with the wall of the container This creates pressure

7. POINT > Identify the FIVE assumptions about an “ideal gas” 3. There are no attractive forces between molecules Gas molecules are moving too fast Gas molecules are too far apart Intermolecular forces are too weak

8. POINT > Identify the FIVE assumptions about an “ideal gas” 4. Collisions between gas particles and between container walls are “elastic” No net loss of total kinetic energy Kinetic energy can be transferred between two particles during collisions Total kinetic energy remains the same as long as temperature remains the same

9. POINT > Identify the FIVE assumptions about an “ideal gas” 5. All gases at the same temperature have the same average kinetic energy The energy is proportional to the absolute temperature Absolute temperature = Kelvin scale ( ̊ K = ̊ C + 273) K e = ½ mv 2 K e = kinetic energy m = mass v = velocity

10. WB CHECK: Which is not an assumption about an ideal gas? a) Gas particles are relatively far apart b) Gas particles exert pressure on the walls of a container due to collisions c) When gas particles collide they lose a small amount of kinetic energy d) Gaseous N 2 and H 2 O at the same temperature will have the same average kinetic energy

11. WB CHECK: You know from your understanding of polar bonds that water molecules are attracted to each other. Give 2 reasons why hydrogen bonds don’t form between water molecules when water is in a gas state:

12. WB CHECK: K e = ½ mv 2 tells you that a) all gas particles move at the same velocity b) all gas particles have the same mass c) collisions between gas particles are elastic d) smaller gas particles have greater velocity

13. POINT > Describe properties of gases explained by KMT Expansion: Gases fill any container in which they are enclosed, regardless of shape or volume

14. POINT > Describe properties of gases explained by KMT Expansion: Gases fill any container in which they are enclosed, regardless of shape or volume Fluidity: Gas particles move past each other easily, without interaction, enabling gases to flow

15. POINT > Describe properties of gases explained by KMT Low density: Particles are relatively far apart (~1000x more so than liquids or solids) Compressibility: Gases are easily compressed relative to liquids or solids, because particles are so far apart

16. POINT > Describe properties of gases explained by KMT Diffusion: Gases readily diffuse and mix with other gases, due to random motion of both gases Effusion: Gases will move through a tiny opening between vessels until concentrations are equal in both

17. WB CHECK: Which property of gases is shown below?

18. WB CHECK: Which two properties of gases are shown below?

19. POINT > Recognize conditions that cause real gases to deviate from “ideal” gas behavior Most gases act like ideal gases under normal conditions Noble gases, and nonpolar gases like N 2, H 2 behave ideally under the widest range of conditions

20. POINT > Recognize conditions that cause real gases to deviate from “ideal” gas behavior Polar gas particles, such as NH 3 or H 2 O deviate more than nonpolar gases due to intermolecular interactions Very low temperature or very high pressure will cause gases to deviate from ideal behavior. Why?

21. WB CHECK: Which gas would be more likely to deviate from ideal gas behavior, Cl 2 or HCl? Why?

22. Homework: Read Pages 311-314 Complete #1-6 Page 314