1. Thermal Physics Thermal Physics is the study of temperature and heat and how they effect matter. Heat leads to change in internal energy which shows as a change of temperature and is evident with the expansion or contraction of matter

2. Temperature Temperature is the hotness or coldness of matter Heat energy travels from a hot object to a cold object If two objects are in contact thermal contact energy can be exchanged between them The exchange of energy is called heat

3. Thermal Equilibrium Two objects are in thermal equilibrium if they are in contact and no exchange of energy takes place Zeroth Law of Thermodynamics states that if object A and B are in thermal equilibrium with object C then A and B are in thermal equilibrium with each other. Two objects in thermal equilibrium have the same temperature.

4. Thermometers A thermometer is a calibrated device to measure temperature. They are much smaller than the system so they can reach equilibrium without great loss of energy from the system.

5. Types of Thermometers Change in volume of liquid (Mercury) Length change of a solid Change of pressure of gas with constant volume. (change of v with constant p) Electric resistance of a conductor Change of color of a hot object

6. Temperature Scales Kelvin calibrated using a gas thermometer Absolute zero = 0 Kelvin = - 273.15c Triple point of water is where ice, water and water vapor coexist. At 0.01 o c and 4.58 mm Hg is used to establish Kelvin scale. Celcius scale T C = T K - 273.15 Fahrenheit scale T F = 9/5T C + 32

7. Thermal expansion of solids and liquids As the temperature of a substance increases the volume increases. Thermal expansion occurs due to a change in the average separation of the constituent atoms or molecules. Atoms in a solid a separated by an average of 10 -10 m and vibrate. As temperature increases so does the separation.

8. Linear Expansion Let L o be the original length  be the coefficient of linear expansion ΔT be the change in temperature Then ΔL =  L o ΔT Coefficient are published values particular to the type of material

9. Area Expansion Let the lengths of the sides be = L then A = L 2 let A o = original area ΔA =  A o ΔT  is the coefficient of area expansion

10. Volume Expansion Similar to both length and area expansion volume expansion can be shown as Δv =  v o ΔT  is the coefficient of volume expansion Note that  = 2  and  = 3  Liquids generally have volume coefficients ten times greater than solids

11. Ideal Gas An ideal gas is one that has atoms or molecules that move randomly and have no long range forces on each other. Each particle is like a point. 1 Mole of gas has 6.02*10 23 particles 1 mole of gas occupies 22.4 liters

12. Ideal Gas Equation Pv = nRT R is the ideal gas constant R= 8.31 when using Pa and m 3 R= 0.0821 when using atmospheres and liters

13. Kinetic Theory of Gases The number of atoms/ molecules in a gas are large and the average separation is great compared to their size particles obey Newton’s laws of motion and move randomly Particles interact only through short range forces having elastic collision, including walls All molecules in a gas are identical

14. Boltzmann’s Constant From Pv = nRT you get Pv = k B RT where k B = n/N A N A = Avogadro’s number = 6.02 * 10 23

15. Force on Container Walls F = N/3(mv 2 /d) where N = number of particles m = mass of one particle v = the average speed of the particles d = the length of the edge of the container Total pressure on the walls of the container P = 2/3(N/v c )(1/2mv 2 ) v c = container volume

16. Molecular Interpretation of Temperature Temperature of a gas is a direct measure of the average molecular kinetic energy of the gas particles. 1/2mv 2 = 3/2k B T Total translational kinetic energy of N particles KE total = N(1/2mv 2 ) = 3/2Nk B T For monatomic gases translational KE is the only type of energy the particles have. Where U = 3/2nRT

17. Diatomic and polyatomic gases have additional energies due to vibration and rotation. Their average velocity is calculated from v rms = m = molar mass in kg per mole Root-Mean-Square