1. Thermodynamics: Measuring Energy in Chemical and Physical Changes (Chapter 13 & 14)

2. Ch. 13/14 Overview What is Energy? Why measure Energy? Thermodynamic Concepts The First Type of Energy Calculations –Specific Heat –Heat of Fusion

3. What is Energy? Energy (q) is the ability to do work or supply heat

4. By Measuring Energy We Can… Understand Physical Changes –Why copper and aluminum pans heat faster than stainless steel –The temperatures at which a liquid will evaporate or freeze Harness the Power of Chemical Reactions –Thermochemistry Predict the Behavior of a Gas –The Gas Laws Find Ways to Do Useful Things –Make fuel efficient car engines –Create air conditioners

5. Thermodynamic Concepts I.Enthalpy (H) is the total energy of a system Enthalpy is a combination of the –internal energy » Kinetic (energy of motion) - how fast all the matter is moving » Potential (stored energy) »Chemical Bonds »Position or Arrangement of the Matter –external energy »energy supplied to a system by its surroundings gases »solids, liquids and gases can absorb or release energy from a difference in temperature (heat) gases »or gases can absorb or release energy from work - changing pressure & volume *total energy of a system cannot easily be measured, however changes in energy can – changes in energy are called “  H”

6. II.A “System”

7. What is the System, and How is Energy Moving in and out?

9. Thermodynamics and Heat III.Thermodynamics = Measuring changes in Energy It is difficult to measure every type of energy (H) in most systems because there are so many ways that energy can be distributed. Scientists most often measure the transfer of energy between a system and its surroundings (  H) V.“Heat” is Energy Absorbed or Released because of a difference in temperature It is the amount of energy transferred between a system and it’s surroundings

10. The types of “Heat” we will measure… Temperature Changes (kinetic energy) Specific Heat Melting or Freezing (phase change) Heat of Fusion Heat of Vaporization Chemical Reactions (energy of chemical bonds) Heat of Reaction Heat of Combustion Solids that Dissolve or Precipitate (energy of physical bonds) Heat of Solution The “ΔH” is a measure of the energy change in a system 1.The amount of energy absorbed or released is always the same in both directions of a process - energy added is always equal to energy released 2.We can add individual inputs of energy together to determine the total amount of energy absorbed or released (Hess’s Law)

11. Lesson 13-1: Physical Change Heat Capacity pg. 508-516 Endothermic –Energy added Exothermic –Energy given off Heat Capacity –Amount of energy needed to raise temperature by 1°C Specific Heat (C) –Amount of energy needed to raise 1 g of a substance by 1°C

12. 13-1: Specific Heat pg. 508-516 Specific Heat (C) –Amount of energy needed to raise temperature of 1 g of a material by 1°C The equation can be rearranged to: q = m C ∆T

13. 13-1: Specific Heat Conceptual Questions Energy changes in an object are affected by both the mass and motion within the material More mass = can absorb more energy Motion of molecules = the freedom of molecules moving affects how energy is distributed: Vibration, Rotation and Translation CONCEPT QUESTIONS Which gets hot fastest on a sunny summer day? metal dog dish OR a metal dog dish full of water Metal dog dish full of water OR a swimming pool –How do your answers relate to mass and freedom of motion of molecules?

14. Homework 13-1 Lesson Questions Heat and Its Measurement WS

15. Working Classroom Examples