2. The Chocolate Chip Challenge: How many grams of salt would you need to give you the number of sodium ions that could be transported by the energy in one chocolate chip? (1 chocolate chip has 3.5 Calories) Last time, we calculated that it takes 4.36 x 10 -21 calories to transport 1 Na + ion out of the cell.

3. Last time…Last time…  System and Surroundings  Exothermic  Endothermic  Heat Transfer (q warmer = -q cooler )  Thermal Equilibrium  Heat Capacity

4. Warm up question (no pun intended): You grab your Pop Tart from the toaster with bare hand and bite into it, only to suffer a terrible burn when the filling hits your tongue. You fingers, however, are fine. What can you deduce from this? 1.The heat capacity of the crust is higher than the heat capacity of the jelly filling. 2.The heat capacity of the jelly filling is higher than the heat capacity of the crust. 3.The heat capacity of the filling and the crust are the same. 4.Pop Tarts are hazardous to your health.

6. What happens to thermal (heat) energy? When objects of different temperature meet:  Warmer object cools  Cooler object warms  Thermal energy is transferred q warmer = - q cooler  specific heat x mass x  T = specific heat x mass x  T warmer object cooler object

7. Determining the Heat Capacity of a MetalDetermining the Heat Capacity of a Metal 106.1g metal T i = T f = c= ? 100g H2O T i = T f = c= 4.18 J/g°C

9. Example: Heat Transfer, Predicting Final Temperature  If we mix 250 g H 2 O at 95 o C with 50 g H 2 O at 5 o C, what will the final temperature be?

10. Example: Heat transfer, determining the initial temperature of one of the two substances  A 400g piece of iron is heated and then dropped into a beaker containing 1000g of water. The original temperature of the water was 20°C, but it is 32.8 after both have come to the same temperature. What was the original temperature of the iron bar?

11. What is enthalpy?What is enthalpy?  Enthalpy =  Enthalpy is:  Hard to measure directly  Related to the total heat content of a system  H = E + PV  Low enthalpy = stable system (e - strongly attracted to nuclei)  At constant pressure, the enthalpy change is equal to the heat exchanged. (sign of Δ H?) Δ H= q

12. Enthalpy  Endothermic  Absorbs E from surroundings  H products > H reactants  Δ H= +  Exothermic  Releases heat to surroundings  H products < H reactants  Δ H= -

13. What happens to thermal (heat) energy?What happens to thermal (heat) energy?  Warms another object (transfer)  Causes a change of state  Is used in an endothermic reaction

15. Thermal Energy and Phase Changes First: What happens?

16. Thermal Energy and Phase Changes First: What happens?