1. APHY201 6/14/2016 1 13.1 Atomic Theory of Matter   Based on analysis of chemical reactions   Brownian motion Brownian motion 1827 – first observed in pollen grains 1905 – Einstein explains motion and calculates the average atomic diameter to be ~10 -10 m

2. APHY201 6/14/2016 2 13.2 Temperature and Thermometers   Variations result in changes to the size/shape and electrical resistance of materials.   Calibration using water – why? Problems concerning pressure   Mercury vs. Alcohol

3. APHY201 6/14/2016 3 13.4 Thermal Expansion   The separation of atoms in a material is related to its temperature.   ΔL = αL o ΔTfor solids   ΔV = βV o ΔTfor solids, liquids, gases   Applications: thermostats, Pyrex glass, bridges, sidewalks, sea levels

4. APHY201 6/14/2016 4 13.4 Thermal Expansion   Water contracts when warmed from 0°C to 4°C then expands. Fish, water pipes, road repair in the northern US

5. APHY201 6/14/2016 5 13.6 The Gas Laws and Absolute Temperature   The volume of a gas depends on pressure and temperature. Equation of State and equilibrium   Boyle’s Law: PV = constant (T = constant)

6. APHY201 6/14/2016 6 13.6 The Gas Laws and Absolute Temperature   Charles’s Law: V/T = constant (P = constant) Absolute zero and the Kelvin scale   Gay-Lussac’s Law: P/T = constant (V = constant) Example: a closed container that is heated or cooled.

7. APHY201 6/14/2016 7 13.7 The Ideal Gas Law   Combining the previous gas laws and including the amount of gas, we find that PV α mT → PV = nRT   n is the number of moles of a gas   R is the universal gas constant 8.314 J/(mol K)

8. APHY201 6/14/2016 8 13.9 Avogadro’s Number   The ideal gas law can also be written in terms of the number of molecules in the gas. PV = NkT   N = nN A with N A = 6.02 x 10 23 molecules/mol   k is the Boltzmann constant 1.38 x 10 -23 J/K

9. APHY201 6/14/2016 9 In class: Problems 10, 29 Other problems ↓ 11. The density at 4 o C is When the water is warmed, the mass will stay the same, but the volume will increase according to Equation 13-2. The density at the higher temperature is

10. APHY201 6/14/2016 10 45. We assume that the last breath Galileo took has been spread uniformly throughout the atmosphere since his death. Multiply that factor times the size of a breath to find the number of Galileo molecules in one of our breaths.