Larry Emme Chemeketa Community College

1. Properties of Matter Chapter 4 Larry Emme Chemeketa Community College

2. Properties of Substances

3. Properties of a Substance • A property is a characteristic of a substance. • Each substance has a set of properties that are characteristic of that substance and give it a unique identity.

4. Physical Properties

5. The inherent characteristics of a substance that are determined without changing its composition. • Examples: • taste • color • physical state • melting point • boiling point

6. Physical Properties of Chlorine • 2.4 times heavier than air • color is yellowish-green • odor is disagreeable • melting point –101oC • boiling point –34.6oC

7. Chemical Properties

8. Describe the ability of a substance to form new substances, either by reaction with other substances or by decomposition.

9. Chemical Properties of Chlorine • It will not burn in oxygen. • It will support the combustion of certain other substances. • It can be used as a bleaching agent. • It can be used as a water disinfectant. • It can combine with sodium to form sodium chloride.

11. Physical Changes

12. Physical Changes • Changes in physical properties (such as size shape and density) or changes in the state of matter without an accompanying change in composition. • Examples: • tearing of paper • change of ice into water • change of water into steam • heating platinum wire

13. Chemical Changes

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

15. 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 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.

16. Formation of Copper(II) Oxide Copper(II) oxide is made up of Cu2+ and O2- Neither Cu nor O2 contains Cu2+ or O2- A chemical change has occurred.

17. Chemical Equations

18. Chemical symbols can be used to express chemical reactions

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

21. Conservation of Mass

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

23. 46.0 g 32.1 g mass reactants = sodium + sulfur  sodium sulfide 78.1 g → 78.1 g reactant 78.1 g product mass products

24. Heat: Quantitative Measurement

25. A form of energy associated with small particles of matter. Heat • A measure of the intensity of heat, or of how hot or cold a system is. Temperature

26. Units of Heat Energy

27. The SI unit for heat energy is the joule (pronounced “jool” rhymes with fool). Another unit is the calorie. (exactly) 4.184 Joules = 1 calorie 4.184 J = 1 cal This amount of heat energy will raise the temperature of 1 gram of water 1oC.

28. Specific Heat

29. The specific heat of a substance is the quantity of heat required to change the temperature of 1 g of that substance by 1oC.

30. Specific Heat of Substances

31. The units of specific heat in calories are:

32. The relation of mass, specific heat, temperature change (Δt), and quantity of heat lost or gained is expressed by the general equation: Heat (cal) = mass (g)  specific heat (cal/g C)  Δt (C)

33. Example

34. 391.5 cal 0.113 cal g C = Calculate the specific heat of a solid in cal/goC if 391.5 cal raise the temperature of 125 g of the solid from 25.0oC to 52.6oC. heat = (mass)(specific heat)Δt heat = (g)(specific heat)Δt heat = 391.5 cal mass = 125 g Δt = 52.6oC – 25.0oC = 27.6oC

35. Energy in Chemical Changes

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

37. Energy Release From Chemical Sources

38. Chemical Changes Caused by Absorption of Energy

39. The End