1. Thermochemistry

2. Energy Changes

3. Energy The ability to do work Types of energy
chemical, mechanical, light, heat, electrical, sound

4. Law of Conservation of Energy
Energy cannot be created or destroyed
It only changes from one form to another

5. Almost all chemical reactions have a change in energy
Energy can be added (endothermic)
Energy can be given off (exothermic)
Thermochemistry studies those changes and their effects

6. A chemical reaction that releases energy is exothermic, and the energy of the products is less than the energy of the reactants.

7. In an endothermic reaction, the products have a larger energy than the reactants, and the reaction absorbs energy.

8. Remember Temperature is the average kinetic energy of a substance
Measured in Kelvins (K)
Heat is the energy transferred during a reaction
Measured in Joules (J)
Always moves from high temperature to low temperature

9. Heat and Temperature
The energy absorbed or released as heat is measured in a calorimeter.
Known quantities of reactants are sealed in a reaction chamber that is immersed in a known quantity of water.
Energy given off by the reaction is absorbed by the water, and the temperature change of the water is measured.
From the temperature change of the water, it is possible to calculate the energy as heat given off by the reaction.

11. Specific Heat The amount of energy transferred depends on
the kind of material involved
on its mass.
The specific heat of a substance is the amount of energy required to raise the temperature of one gram by 1°C or 1 K.
Materials with a high specific heat absorb more energy before their temperature changes

12. Sample Specific Heats

13. Specific Heat Problems
energy gained or lost with a change of temperature can be calculated using the following equation.
q=cmΔT

14. A 4.0 g sample of glass was heated from 274 K to 314 K, a temperature increase of 40. K, and was found to have absorbed 32 J of energy as heat.
a. What is the specific heat of this type of glass?
b. How much energy will the same glass sample gain when it is heated from 314 K to 344 K?

15. If 220. 0g of steam at 350. 0 °C absorbs 550
If 220.0g of steam at °C absorbs kJ of heat energy, what will be its increase in temperature? What is it’s final temperature?

16. When 80. 0 grams of a certain metal at 90. 0 °C was mixed with 100
When 80.0 grams of a certain metal at 90.0 °C was mixed with grams of water at 30.0 °C, the final equilibrium temperature of the mixture was 36.0 °C. What is the specific heat (J/g °C) of the metal?