Chemistry Chapter 4

1. Properties of Matter Chapter 4

2. Chapter Outline 4.1 Properties of Substances 4.2 Physical Changes 4.3 Chemical Changes 4.4 Conservation of Mass 4.5 Energy 4.6 Heat: Quantitative Measurement 4.7 Energy in Chemical Changes 4.8 Conservation of Energy

3. Properties of Substances

5. Physical Properties

8. Chemical Properties

12. Physical Changes

14. Chemical Changes

15. In a chemical change new substances are formed that have different properties and composition from the original material.

16. Formation of Copper(II) Oxide Heating a copper wire in a Bunsen burner causes the copper to lose its original appearance and become a black material. The black material is a new substance called copper(II) oxide. Copper is 100% copper by mass. Copper (II) oxide is: 79.94% copper by mass and 20.1% oxygen by mass. The formation of copper(II) oxide from copper and oxygen is a chemical change. The copper (II) oxide is a new substance with properties that are different from copper.

17. Formation of Copper(II) Oxide Copper(II) oxide is made up of Cu 2+ and O 2- Neither Cu nor O 2 contains Cu 2+ or O 2- A chemical change has occurred. 4.2

18. Water is decomposed into hydrogen and oxygen by passing electricity through it. Decomposition of Water The composition and physical appearance of hydrogen and oxygen are different from water. The hydrogen explodes with a pop upon the addition of a burning splint. The oxygen causes the flame of a burning splint to intensify. They are both colorless gases. But the burning splint is extinguished when placed into the water sample.

19. Chemical Equations

20. Water decomposes into hydrogen and oxygen when electrolyzed. reactant products yields

21. Chemical symbols can be used to express chemical reactions

22. Water decomposes into hydrogen and oxygen when electrolyzed. reactant yields 2H 2 O 2H 2 O 2 products

23. Copper plus oxygen yields copper(II) oxide. yield product reactants heat

24. Copper plus oxygen yields copper(II) oxide. heat yield product reactants 2Cu O 2 2Cu 2 O

26. Conservation of Mass

27. No change is observed in the total mass of the substances involved in a chemical change.

28. sodium + sulfur  sodium sulfide 78.1 g 78.1 g product mass products 78.1 g reactant -> 46.0 g 32.1 g mass reactants =

29. Energy

30. Energy is the capacity to do work

32. Potential Energy Energy that an object possesses due to its relative position.

33. The potential energy of the ball increases with increasing height. increasing potential energy 50 ft 20 ft increasing potential energy

34. Potential Energy Stored energy.

36. Kinetic Energy Energy matter possesses due to its motion.

41. Heat: Quantitative Measurement

43. Units of Heat Energy

45. An Example of the Difference Between Heat and Temperature A form of energy associated with small particles of matter. A measure of the intensity of heat, or of how hot or cold a system is.

46. Twice as much heat energy is required to raise the temperature of 200 g of water 10 o C as compared to 100 g of water. 200 g water 20 o C A 100 g water 20 o C B heat beakers temperature rises 10 o C 100 g water 30 o C 200 g water 30 o C 4184 J 8368 J

47. Specific Heat

48. The specific heat of a substance is the quantity of heat required to change the temperature of 1 g of that substance by 1 o C.

53. Example 1

54. Calculate the specific heat of a solid in J/g o C and in cal/ g o C if 1638 J raise the temperature of 125 g of the solid from 25.0 o C to 52.6 o C. (mass of substance)(specific heat of substance) Δ t = heat (g)(specific heat of substance) Δ t = heat heat = 1638 J mass = 125 g Δ t = 52.6 o C – 25.0 o C = 27.6 o C

55. Calculate the specific heat of a solid in J/g o C and in cal/ g o C if 1638 J raise the temperature of 125 g of the solid from 25.0 o C to 52.6 o C. Convert joules to calories using 1.000 cal/4.184 J

56. Energy in Chemical Changes

57. In all chemical changes, matter either absorbs or releases energy .

58. Energy Release From Chemical Sources Chemical changes occurring within body cells. Body Combustion of fuels. Heat and Light A lightstick. Fuel combustion. Light Storage batteries Electrical Energy Source Type of Energy

59. Chemical Changes Caused by Absorption of Energy Photosynthesis in green plants. Light Electroplating of metals. Decomposition of water into hydrogen and oxygen Electrical Chemical Change Type of Energy

60. Conservation of Energy

62. 4.4 H 2 + O 2 have higher potential energy than H 2 O Electrolysis of Water Burning of Hydrogen in Air energy is given off energy is absorbed higher potential energy lower potential energy

63. Law of Conservation of Energy Energy cannot be created or destroyed, it can only change forms.

64. The End