1. Introduction to Thermodynamics Gas Laws

2. Thermal Expansion in solids Podcast: KQED Quest Lab: “Bridge Thermometer” from 5/4/2010 Thermal Expansion Eq: (in list)

3. Thermodynamics Thermodynamics is the study of heat and thermal energy. Thermal properties (heat and temperature) are based on the motion of individual molecules, so thermodynamics is a lot like chemistry.

4. Total energy E = U + K + E int – U: potential energy – K: kinetic energy – E int : internal or thermal energy Potential and kinetic energies are specifically for “big” objects, and represent mechanical energy. Thermal energy is related to the kinetic energy of the molecules of a substance.

5. Temperature and Heat Temperature is a measure of the average kinetic energy of the molecules of a substance. Think o it as a measure of how fast the molecules are moving. The unit is O C or K. Temperature is NOT heat! Heat is the internal energy that is transferred between bodies in contact. The unit is Joules (J), or sometimes calories (cal). A difference in temperature will cause heat energy to be exchanged between bodies in contact. When two bodies are at the same temperature, no heat is transferred. This is called Thermal Equilibrium.

6. Ideal Gas Law P 1 V 1 / T 1 = P 2 V 2 / T 2 – P 1, P 2 : initial and final pressure (any unit) – V 1, V 2 : initial and final volume (any unit) – T 1, T 2 : initial and final temperature (in Kelvin!) Temperature in K is obtained from temperature in o C by adding 273.

7. Sample problem Suppose an ideal gas occupies 4.0 liters at 23 o C and 2.3 atm. What will be the volume of the gas if the temperature is lowered to 0 o C and the pressure is increased to 3.1 atm.

8. Ideal Gas Equation P V = n R T – P: pressure (in Pa) – V: volume (in m 3 ) – n: number of moles – R: gas law constant 8.31 J/(mol K) – T: temperature (in K)

9. Sample problem Determine the number of moles of an ideal gas that occupy 10.0 m 3 at atmospheric pressure and 25 o C.