1. Bellringer 11/30
Determine the Kelvin temperature required for mole of gas to fill a balloon to 1.20 L under atm pressure.

2. Bellringer 12/3
A rigid container of O has a pressure of 340 kPa at a temperature of 713 K. What is the pressure at 273K?

3. Bellringer 12/4
A 50.6 g sample of iron metal is heated from 19.7o C to 24.3o C. How many joules of heat will be absorbed? (specific heat of iron is (J/g oC)

4. Thermochemistry

5. Energy Energy – the ability to do work or produce heat
Exists in 2 forms:
Kinetic energy – energy of motion
Potential energy – energy at rest or energy of position

6. Energy
Kinetic energy – in a chemical reaction temperature is the determining factor
The higher the temperature…the faster the particles move…the more kinetic energy
Potential energy – in a chemical reaction deals with the types of atoms & what bonds the form

7. Law of Conservation of Energy
Law of Conservation of Energy – Energy is neither created nor destroyed

8. Heat (q)
Heat or energy can be in joules, calories, kilocalories, or kilojoules
The SI unit is the Joules (J)
1000 cal = 1 Cal
1 cal = 4.18 J
340 Cal x 1000cal/1cal x 4.18J/1 cal = J

9. Specific Heat
Specific Heat (c) – the amount of heat required to raise 1 gram of a substance by 1C
Specific heat is an intensive property
Every substance has its own specific heat

10. Specific Heat q = mcT q = heat (J) m = mass (g)
c = specific heat (j/gC)
T = change in temperature = Tf-Ti (C)

11. Specific Heat
A 10.0 g sample of iron changes temperature from 25.0C to 50.4 C while releasing 114 joules of heat. Calculate the specific heat of iron.

12. Another example
If the temperature of 34.4 g of ethanol increases from 25.0 C to 78.8 C how much heat will be absorbed if the specific heat of the ethanol is 2.44 J/g C

13. Yet another example
4.50 g of a gold nugget absorbs 276 J of heat. What is the final temperature of the gold if the initial temperature was 25.0 C & the specific heat of the gold is 0.129J/g C

14. Endothermic & Exothermic Reactions
Endothermic reactions – chemical reaction that requires energy to break existing bonds
Heat goes into the reaction from the surroundings
Exothermic reactions – chemical reaction in which energy is released
Heat goes out of the reaction into the surroundings

15. Endothermic & Exothermic Reactions
Endothermic reactions – since heat goes from the surroundings into your system, it will feel cold
Temperature of endothermic reactions goes down
The sign for the heat change will be +
Exothermic reactions – since heat goes from the system to the surroundings, it will feel hot
Temperature of exothermic reactions goes up
The sign for the heat change will be -

16. Endothermic & Exothermic Reactions

17. Endothermic & Exothermic Reactions

18. Endothermic & Exothermic Reactions
Are the following reactions endothermic or exothermic?
CO + 3H2  CH4 + H2O H= -206kJ
I add magnesium metal to some hydrochloric acid. The temperature goes from 23C to 27 C
I mix together some vinegar & baking soda. The temperature goes from 28C to 23C