1. Energy, and Changes

2. Energy & Temperature

3. Energy
Energy is the capacity to do work or produce heat.

4. Energy
Forms:
Radiant
ex. sunlight

5. Energy
Forms:
Radiant – ex. sunlight
Kinetic
energy carried by objects in motion (includes mechanical & thermal)

6. Energy Forms: Potential
Radiant – ex. sunlight
Kinetic – energy carried by objects in motion (includes mechanical & thermal)
Potential
due to position/stored energy (includes electrical & chemical)

7. Energy
Measuring:
calories (cal) – amount of heat needed to raise temperature of 1 g H2O by 1 C
1 cal = 1 g × 1 C
Food energy is in Calories, 1 Cal = 1 kcal

8. Energy Measuring: SI unit is Joule (J)
calories (cal) – amount of heat needed to raise temperature of 1 g H2O by 1 C
1 cal = 1 g * 1 C
Food energy is in Calories, 1 Cal = 1 kcal
SI unit is Joule (J)

9. Energy
Measuring:
SI unit is Joule (J), 1 J is about the energy to lift a medium-sized apple 1 meter from ground
1 cal = J

10. Energy Law of Conservation of Energy:
in any process, energy is neither created nor destroyed

11. Temperature What is temperature?
comparison of how hot or cold an object is with some standard
measure of the average kinetic energy of the particles in a sample of matter

12. Temperature
Units for Temperature
Fahrenheit
Celsius
Kelvin (SI units)

13. Temperature Units for Temperature Kelvin (SI units)
Fahrenheit
Celsius
Kelvin (SI units)
Why don’t we use a degree mark with Kelvin temperatures?
What is the lowest Kelvin temperature?
Why do we call it absolute zero?

14. Temperature Units for Temperature A quick look at the three scales.
0 C = 273 K = 32 F
100 C = 373 K = 212 F

15. Temperature
Converting Fahrenheit/Celsius
C = 5/9 × (F – 32)

16. Temperature
Convert 98.6 F to C
37 °C

17. Temperature
Convert 25 C to F
77 °F

18. Temperature
Converting Kelvin/Celsius
C = K – 273

19. Temperature
Convert 399 K to C
126 °C

20. Temperature
Convert 25 C to K.
298 K

21. Changes of State

22. Changes of State
Energy and change of state…
To change states, particles must overcome the attractive forces holding them together (the number of particles does not change)

23. Changes of State
Vaporization
Liquid changes to a gas, also called evaporation, requires energy input

24. Changes of State Vaporization
Liquid changes to a gas, also called evaporation, requires energy input
Rapidly moving particle near surface of liquid gains enough energy to escape attractive forces of other particles

25. Volatile liquid – one that readily evaporates
Changes of State
Vaporization
Liquid changes to a gas, also called evaporation, requires energy input
Rapidly moving particle near surface of liquid gains enough energy to escape attractive forces of other particles
Volatile liquid – one that readily evaporates

26. Changes of State
Boiling point
Temperature at which vapor pressure becomes equal to the atmospheric pressure

27. Changes of State
Heat of vaporization
Amount of heat necessary to vaporize a given amount of liquid

28. Changes of State Heat of vaporization
You have 18.2 moles of water. How much energy is needed to vaporize the sample?
(Molar heat of vaporization for water = 40.7 kJ/mole) kJ

29. Changes of State
Condensation
Gas changes to a liquid, releases energy

30. Changes of State
Freezing (Solidification)
Particles get closer together and more organized than in the liquid state, releases energy

31. Changes of State
Melting (Liquefying)
Particles become less organized and farther apart, requires energy input

32. Changes of State
Melting
Melting point - temperature at which solid and liquid form of substance exist in equilibrium, also called freezing point

33. Changes of State
Melting
Heat of fusion - amount of heat needed to convert a given amount of solid into a liquid

34. Changes of State Melting
You have a 278 mole block of ice. How much energy is needed to melt it?
(Molar heat of fusion for water = 6.00 kJ/mole)
1668 kJ

35. Changes of State
Sublimation
Solid changes directly to a gas, requires energy input

36. Changes of State
Deposition
Gas changes directly to a solid, releases energy

37. Changes of State
Heating curves
Describe changes of state of matter, plot of sample temperature as a function of time

38. Changes of State

39. Changes of State
Phase diagrams
Relates states of matter to temperature and pressure

40. Changes of State