2. A. Kinetic Molecular Theory Kinet ic Theory of Matter Tiny, constantly moving particles make up all matter. Tem perature A measure of the average kinetic energy of particles in matter The kinetic energy (motion) of these particles increases as temperature increases.

3. Temperature SI unit? Subtract 273 from a temperature in Kelvin to convert to degrees Celsius. Temperature is a measure of molecular movement. 0 Kelvin is NO movement. Absolute zero.

4. Thermal Energy The sum of the kinetic and potential energies of all the particles in an object Potential energy: stored energy of an object due to its position.

5. Thermal Energy Does the ball rolling have more/less/same thermal energy as the stationary ball?

6. Heat Is thermal energy that flows from something at a higher temperature to something at a lower temperature.

7. Specific Heat The amount of thermal energy needed to raise the temperature of 1 kg of a material 1 degree Celsius. Which heats up faster? The land or water?

8. Specific Heat Which heats up faster? The land or water? C water = 4184 J / kg °C C sand = 664 J / kg °C for equal amounts of sand/water, requires about 6x the thermal energy

9. Thermal Energy Equation The thermal energy of an object changes as its temperature changes Change in thermal energy (Q) = J Mass (m) = kg Change in temperature (T) = °C Specific heat (C) = J/kg °C Q = m(T f – T i ) C

10. Problem The air in a living room has a mass of 72 kg and a specific heat of 1,010 J/kg °C. What is the change in thermal energy when the air warms from 20 to 25°C? Given: m = 72 kg C = 1010 J/kg °C T f – T i = 25 – 20 = 5°C Q = ? Equation:Q = m(T f – T i ) C Q = ( 72 kg) ( 25-20 °C) ( 1010 J/kg °C) Q = 363,600 J (joules)

11. Measuring Specific Heat A calorimeter is used to help measure the specific heat of a substance. 1. Mass the sample 2. Initial temperature of water in calorimeter 3. Material added to inner chamber 4. As cools, thermal energy transferred to water and temp of water increases 5. Initial and final temps of water are known. 6. Energy absorbed by water can be calculated by temp change of fixed mass 7. Thermal energy released = absorbed 8. Can calculate specific heat Q = m(T f – T i ) C

12. Measuring Specific Heat Water Mass = 100 g or 0.1 kg Change in temp = ? C water = 4,184 J/kg °C CAN SOLVE FOR Q! Energy in = Energy out Calcium Chloride Mass = 6 g or 0.006 kg Change in temp = same Q = same Solve for C (specific heat!) Q = m(T f – T i ) C

14. Four States of Matter There are four states of matter created by the differences in the attraction between particles.

15. Solid State Low KE, particles vibrate but can’t move around. Because of strong attraction between particles, solids have a fixed volume and shape.

16. Liquid State Higher KE – particles can move around but are still close together. Indefinite shape – takes the shape of the container Definite volume

17. Gas State High KE – particles can separate and move throughout container. Particles are much farther apart and attractive forces are weak so particles no longer cling together. Indefinite shape and volume; Spread evenly in container through diffusion

18. Plasma State Very high KE – particles collide with enough energy to break into charged particles (+/-) Gas-like, indefinite shape and volume Stars, fluorescent light bulbs, TV tubes contain plasmas Most common state of matter in universe. Link

19. Phase Changes Changes in the thermal energy of a material can cause it to change from one state to another. Melting Solid to liquid Freezing Liquid to solid Melting point = freezing point

20. Changing States - Melting As temperature increases, particles move faster and attractive force can’t keep them in place. Temperature at which a solid begins to melt is its melting point.

21. Changing States - Melting The amount of energy required to change 1 kg of a substance from a solid to a liquid at its melting point is the heat of fusion.

22. Changing States - Freezing Lowering temperature of a liquid decreases the particles’ average KE and they move slower. Attractive forces are strong enough to create an ordered arrangement. The heat of fusion is also the energy released when a liquid freezes.

23. Phase Changes Vaporization (boiling) Liquid to gas at the boiling point Evaporation Liquid to gas below the boiling point Condensation Gas to liquid

24. Changing States - Vaporization Liquid to gas at the boiling point As temperature of a liquid increases, the particles move faster and farther apart. The forces between them become so weak that the particles no longer cling together.

25. Changing States - Vaporization Vaporization at the surface of a liquid is called evaporation. Evaporation causes the temperature of the liquid to decrease. Vaporization that occurs within the liquid is called boiling.

26. Changing States - Vaporization The boiling point is the temperature at which the pressure of the vapor in the liquid equals the pressure acting on its surface. The heat of vaporization is the amount of energy required for 1 kg of liquid at its boiling point to become a gas.

27. Changing States - Condensation Condensation – when a gas changes to a liquid The heat of vaporization is also the amount of energy released during condensation.

28. Heating Curve of a Substance Kinetic Energy Motion of particles Related to temperature Potential Energy Space between particles Related to phase changes video

29. Heating Curves Heat of vaporization Heat of fusion

30. Thermal Expansion Most matter expands when heated and contracts when cooled.  Temp causes  KE. Particles collide with more force & spread out. An expansion joint allows concrete to expand and contract without damage. Thermometers? Drawers and cabinets? Water?

32. Ways to Transfer Thermal Energy Conduction Convection Radiation

33. Definitions Transfer of thermal energy between colliding particles is ______________ Transfer of thermal energy in a fluid by the movement of the fluid from place to place is _______________. Transfer of thermal energy by electromagnetic waves: ______________. conduction convection radiation

34. Identify

35. Thermal Conductors Thermal energy can be transferred by conduction in ALL materials The rate at which thermal energy is transferred VARIES by material Materials that transfer thermal energy easily are called thermal conductors Solids and liquids are faster conductors than gases (solid > liquid > gas) WHY? Best thermal conductors are metals

36. Convection Currents Convection: transfer of thermal energy in a fluid by the movement of the fluid from place to place Convection Currents: Warmer fluids have a different density than a cooler fluid More dense cooler fluid sinks, pushing up warmer fluids Rising and sinking of fluid creates a convection current. Thermal energy transferred by movement of fluid from place to place.

37. Convection Currents Deserts and Rainforests Where is air warmer? Surface or higher altitudes? Equator or poles? Why do we have rainforests at the equator? Dry air carried farther north & south creating a zone of deserts!

38. Radiation and Radiant Energy Radiation: transfer of energy by electromagnetic waves. When radiation strikes, some energy is absorbed, some transferred through the material, and some is reflected. How much does what? Depends on the material

39. Thermal Insulators A material in which thermal energy moves slowly Gases are usually better insulators than solids or liquids Good conductors are poor thermal insulators.

40. Using Thermal Energy Lit a Camp fire Heated a house Mowed the lawn Driven in a car Boiled water

41. Heating Systems: Forced Air

42. Heating Systems: Radiator

43. Heating System: Electric

44. Thermodynamics The study of the relationship between thermal energy, heat and work. How else can you increase the thermal energy of an object besides heating it? A system is anything you can draw a boundary around

45. First Law of Thermodynamics Energy is conserved (cannot be created or destroyed) The increase in thermal energy of a system equals the work done on the system plus the heat added to the system. Open system: thermal energy flows across the boundary or work is done across the boundary of the system. Energy of an open system can change Closed system: No outside work is done or thermal energy flows across boundary. The total energy of the system doesn’t change.

46. Heat flow – hot to cold Increase of TE of colder object = decrease in TE of warmer object Energy is not created or destroyed (1 st law satisfied)

47. Second Law of Thermodynamics It is impossible for heat to flow from a cooler object to a warmer object unless work is done. Entropy in a closed system never decreases Entropy

48. Converting Thermal Energy to Work Heat Engine: a device that converts TE into work. i.e. a car Some energy is always transferred to the surroundings. Internal combustion engine – fuel is burned in the engine in chambers or cylinders. Pistons move up and down in the cylinder in four separate strokes. Intake, Compression, Power and Exhaust page 275.

49. Refrigerators How do refrigerators stay cold? How can thermal energy be moved from a cold area to a warmer area?

50. Entropy A measure of how spread out or dispersed energy is. (randomness or disorder of a system) Entropy increases when energy becomes more spread out. (less concentrated) All events that occur cause the entropy of the universe to increase. (Entropy always increases)universe As energy spreads out it becomes less usable.