Energy Flashcards (units 2, 6, & 7)

1. Energy Flashcards(units 2, 6, & 7)

2. ENERGY The ability to do work

3. Potential Energy Energy of position. Stored energy.

4. Kinetic Energy Energy of motion Depends on how heavy & how fast

5. Radiant Energy Electromagnetic Energy

6. Units of Energy Joules

7. Energy in Chemistry Chemical Potential Energy – stored in chemical bonds Heat – form of energy that flows between objects at different temperatures.

8. Direction of heat flow Hot to Cold

9. Q Symbol for heat energy

10. Temperature A measure of the avg. kinetic energy of the particles of a system. Temperature is NOT energy.

11. As the temperature , the avg. kinetic energy … Increases!

12. As the temperature , the avg. kinetic energy … Decreases!

13. When the temperature is constant, the avg. kinetic energy … is constant!

14. Law of Conservation of Energy Total energy is conserved. Energy before = Energy after Energy lost = Energy gained Energy can be converted from 1 form to another.

15. Environment System Energy Energy of Universe is conserved Universe Energy can move between the system and the environment. Environment

16. Environment System Energy EXO - energy leaves system (exits). Temperature of environment  Temperature of system  System has a net loss in energy! H is –’ve.

17. Exothermic Process System loses energy (heat) to environment.

18. Environment System Energy Endo - Energy enters system (entrance) Temperature of environment . Temperature of system . System has a net gain in energy! H is +’ve.

19. Endothermic Process System absorbs energy (heat) from environment

20. Quantity of heat transferred depends on … Temperature change Mass of substance Specific Heat of substance

21. Calculating Heat Transferred Simple system: Pure substance in a single phase. To calculate heat gained or lost, use: Q = mCT • Q = amount of heat transferred • m = mass of substance • C = specific heat capacity of the substance (Table B). • T = temperature change = Tfinal – Tinitial

22. Q = mCT Equation used to calculate energy change when a substance in 1 phase is heated or cooled.

23. Calculating energy changes in H2O Q C m T

24. Dissolving • When 10 g NaOH dissolves, the temperature of the H2O increases. Add 100 g H2O Styrofoam Cup Close together. Not interacting with H2O. Pulled apart & interacting with H2O.

25. Calorimetry • The NaOH is the system. • The H2O is the environment. Styrofoam Cup Initial temperature of water = 22C Temperature = 30C

26. Calculating energy changes in H2O Q CH2O = 4.18J/g 100g 8 Q = 3344 Joules

27. Exothermic In a calorimetry exp’t, H2O is the environment. If the temperature of the H2O , the process was exothermic. If the temperature of the H2O , the process was endothermic.

28. Energy and Stability If energy is high, stability is low. If enrgy is low, stability is high.

29. Energy Changes at Phase Changes Gas Going Up the ladder = Endothermic Process Net gain in energy. Potential Energy of System Liquid Going Down the ladder = Exothermic Process Net loss in energy. Solid

30. Use this equation to calculate energy changes for phase changes between ice & liquid water at 0C. Calculating Energy Change at Phase Change Q = mHf

31. Use this equation to calculate energy changes for phase changes between steam & liquid water at 100C. Calculating Energy Change at Phase Change Q = mHv

32. Q Q or m Hf m Hv

33. I II III IV V Liquid & Gas Gas Solid & Liquid Liquid Solid Boil pt. K.E. K.E. K.E.↔ K.E.↔ P.E.↔ K.E. P.E. Temperature P.E. Melt pt. P.E.↔ P.E.↔ Time

34. Melting & Boiling Points • Plateaus = Phase changes = Potential energy changes. • Notice that as long as 2 phases are present, the temperature is constant. • Melting point, Boiling point.

35. To analyze a heating/cooling curve: • Does the curve go uphill or downhill? • Label the phases present in each region. • Describe what happens to the K.E. in each region. • Describe what happens to the P.E. in each region. • Locate the melting point and boiling point.

36. What happens to the temperature as heat is added at the boiling point? • Nothing, until only 1 phase is present!

37. The boiling point of a pure substance is … Constant!

38. The melting point of a pure substance is … Constant!

39. 3 equations for Q • Q = mCT • Q = mHf • Q = mHv • Have to figure out which one to use for a given problem. • Depends which section of heating curve. • Look for hints in the problem.

40. Hf Amount of energy required to convert 1 gram of a pure substance from the solid to the liquid phase at the melting point. Heat of Fusion

41. Hv Amount of energy required to convert 1 gram of a pure substance from the liquid to the gas phase at the boiling point. Heat of Vaporization

42. Temperature changed Temperature increased Temperature decreased Initial / Start temperature Final temperature Ending temperature From ____ to ____ Water Q = mCT

43. Q = mHf • Ice • Freezing • Melting • At 0C (for H2O) • At constant temperature

44. Q = mHv • Steam • Boiling • Condensation • At 100C (for H2O) • At constant temperature