1. Kinetic Theory and Gases

2. Gases… (a good mental image) Gases… (a good mental image)

3. Refresher…. Before we talk about the Kinetic Theory, what is a theory in science?

4. The Kinetic Theory of Matter is the explanation of how we believe atoms and molecules, particularly in gas form, behave. A statement of the Kinetic Theory is: 1. All matter is made of atoms, the smallest bit of each element. A particle of a gas could be an atom or a molecule. 2. Atoms have an energy of motion that we feel as temperature. The higher the temperature, the faster the motion. 3. There is a temperature to which we can extrapolate, absolute zero, at which, theoretically, the motion of the atoms and molecules would stop. 4. The pressure of a gas is caused by the motion of the atoms or molecules of gas striking the walls of the container. 5. There is a very large distance between the particles of a gas compared to the size of the particles.

5. Absolute zero A theoretical temperature at which all molecular motion stops. A theoretical temperature at which all molecular motion stops. “Theoretical” temperature because scientists haven’t been able to reach it. (They have come within a billionth of a degree though. Pretty close!) “Theoretical” temperature because scientists haven’t been able to reach it. (They have come within a billionth of a degree though. Pretty close!) Absolute zero would be -460 o F. Absolute zero would be -460 o F. In contrast, the coldest temperature ever recorded in the Earth’s weather is -128 o F. In contrast, the coldest temperature ever recorded in the Earth’s weather is -128 o F.

6. Absolute Zero The Kelvin temperature scale was created so that Zero Kelvin is absolute zero. 0 Kelvins = absolute zero = -273 o C

7. Notice – the Kelvin scale doesn’t use “degrees.”

9. The Kinetic Theory explains these properties of GASES Gases are less dense than solids because there is a lot of space between the particles. Gases are less dense than solids because there is a lot of space between the particles. Gases can be compressed because of the empty space between particles. Gases can be compressed because of the empty space between particles. Random motion of gas particles causes a gas to fill its container. Random motion of gas particles causes a gas to fill its container.

10. DIFFUSION DIFFUSION OF GASES: DIFFUSION OF GASES: Is the intermixing of two or more gases to form a homogeneous mixture without any chemical change.Is the intermixing of two or more gases to form a homogeneous mixture without any chemical change. Diffusion is purely a physical phenomenon.Diffusion is purely a physical phenomenon. Gases diffuse very quickly because of large empty spaces between molecules and the rapid movement of the molecules.Gases diffuse very quickly because of large empty spaces between molecules and the rapid movement of the molecules.

11. Pressure Pressure is measure of the force of the collision of the particles against the side of a container. Pressure is measure of the force of the collision of the particles against the side of a container. Pressure is defined as force per unit area. Pressure is defined as force per unit area. It is normally measured in: It is normally measured in: Atmospheres (atm)Atmospheres (atm) Millimeters of Mercury (mm Hg)Millimeters of Mercury (mm Hg) 1.00 atm = 760 mm Hg1.00 atm = 760 mm Hg

12. What keeps a balloon inflated? Gas molecules inside a volume (e.g. a balloon) are constantly moving around freely. During this molecular motion they frequently collide with each other and with the surface of any enclosure there may be (in a small balloon that would be many thousands of billions of collisions each second).

13. The Gas Laws

14. Pressure Force per unit area

15. The Gas Laws Boyle’s Law Pressure and volume are inversely related at constant temperature. Pressure and volume are inversely related at constant temperature. Boyle's Law states that the pressure exerted by a confined gas is inversely proportional to the volume. Boyle's Law states that the pressure exerted by a confined gas is inversely proportional to the volume. P 1 V 1 = P 2 V 2 P 1 V 1 = P 2 V 2 Boys are pretty violent! Boys are pretty violent!

16. Boyle's law simulation

17. Charles’ Law Volume of a gas varies directly with the absolute temperature at constant pressure. Volume of a gas varies directly with the absolute temperature at constant pressure. V 1 = V 2 T 1 T 2 V 1 = V 2 T 1 T 2 Charles takes Vitamins! Charles takes Vitamins!

18. Gay-Lussac Temperature is directly proportional to pressure. Temperature is directly proportional to pressure. As one variable increases, the other variable also increases As one variable increases, the other variable also increases Memory: George Lopez Takes Pills Memory: George Lopez Takes Pills

19. Combined Gas Law If the amount of gas remains constant, use this formula and cancel out the other things that don’t change. If the amount of gas remains constant, use this formula and cancel out the other things that don’t change.