1. AP Physics Mr. Jean November 1 st, 2011

2. Thermal expansion What went wrong here?

4. Thermal Expansion The equation:  = is the average linear expansion coefficient which is a constant with regards to the material. For reference:  steel = 11  10 -6 /  C

7. Videos/Demo: Video Demo: Ring & Ball

8. Thought question You heat a disc with a hole in it. Will the radius of the hole get larger, smaller, or stay the same? a. a.Larger b. b.Smaller c. c.Stay the same

9. Thought question (ungraded): If the expansion of all of the linear dimensions of an object is proportional to ΔT, what should the expansion of the surface area of the object be proportional to? a. a.ΔT b. b.2ΔT c. c.ΔT 2 d. d.The surface area won’t change with temperature. e. e.None of the above

10. Area & Volume Expansion (of solids) The equations:  = average coefficient of volume expansion

11. Thought question: Two jars of gas: helium and neon. Both have the same volume, same pressure, same temperature. Which jar contains the greatest number of gas molecules? (The mass of a neon molecule is greater than the mass of a helium molecule.) a. a.jar of helium b. b.jar of neon c. c.same number

12. Ideal Gas Law Hold T constant, then V decreases as P increases Hold P constant, then V increases as T increases Hold P, T, constant, then V increases as #molecules increases

13. Ralph is confused…the book calls two different equations “the ideal gas law”: “PV = nRT”, and “PV = Nk B T”. Why are they both called the ideal gas law, when only the first equation looks like what he learned in chemistry? Quick Writing Important stuff: P must be in _______ V must be in _______ T must be in _______ n = ________ R = ________ N = ________ k B = ________ What’s a mole? How are R and k B related?

14. Molecules collide like superballs (elastic) due to repulsive forces No attractive forces Never condense into liquids or solids Are like “frictionless surfaces”, “massless pulleys”, fluids without viscosity, projectiles without air resistance, etc.  That is, they don’t really exist, but are useful constructs Ideal Gases: