1. THERMOCHEMISTRY The study of heat released or required by chemical reactions Fuel is burnt to produce energy - combustion (e.g. when fossil fuels are burnt) CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(g) + energy

2. What is Energy? Energy Kinetic energy (E K ) Potential energy (E P ) Energy due to motion Energy stored in a substance The ability to do work

3. Potential Energy Chemical Energy: energy stored in Chemical bond Stable bonds- the attractive forces outweigh the repulsive forces LOW potential energy

4. Potential Energy Nuclear Energy: in the nucleus, the protons try to repulse each other against the strong nuclear force.

5. Kinetic Energy of molecules Vibrational Rotational Translational

6. Radiant Energy Any form of electromagnetic radiation

7. Heating Solids

9. During a chemical reaction, chemical energy is converted to _________ energy or _______ energy or _______ These changes are the result of bonds breaking where energy is _____________ and then reforming where energy is _____________. kineticradiant heat consumed released Chemical reactions

11. Law of Conservation of Energy Law of Conservation of Energy: the total energy of the universe is constant and can neither be created nor destroyed; it can only be transformed.

12. UNITS OF ENERGY S.I. unit of energy is the joule (J) Heat and work ( energy in transit) also measured in joules 1 kJ (kilojoule) = 10 3 J Calorie (cal): 1 cal is the energy needed to raise the temperature of 1g of water by 1 o C 1 cal = 4.184 J

13. Thermal Energy The total kinetic energy of individual molecules Measured Joules, J

14. Temperature The measure of the average kinetic energy of the molecules

15. HEAT and WORK HEAT is the transfer of thermal energy from a hot object to a colder object. e.g. kettle heats on a gas flame cup of tea cools down (loses energy as heat) This energy can be used to increase the temperature of the object (random molecular motion) or to change state (increase potential energy)

16. Specific heat capacity is the quantity of energy required to change the temperature of a 1g sample of something by 1 o C Specific Heat Capacity (Cs) Heat capacity Mass = J / o C / gJ / o C g = How do we relate change in temp. to the energy transferred?

17. Calculation of Heat, Q We can calculate the Heat, Q, required to raise the temperature of a given mass by a specific temperature using Q = mc∆T Where Q = heat, in J m= mass, in kg c = specific heat capacity, in J/g 0 C ∆T= change in Temp, 0 C

18. Question 1 How much heat is required to heat 600 mL of water from 20 0 C to 85 0 C?

19. Question 2 What is the final temperature if 250.0 J of heat is transferred into 10.0g of methanol initially at 20.0 0 C? (c methanol = 81.6 J/g C)