1. Slide 1 of 25 Chemistry 2.3

2. Slide 2 of 25 © Copyright Pearson Prentice Hall Connecting to Your World Elements and Compounds Take two pounds of sugar, two cups of boiling water, and one quarter teaspoon of cream of tartar. Add food coloring and you have the sticky, sweet concoction known as cotton candy. You will learn how substances are classified as elements or compounds. 2.3

3. © Copyright Pearson Prentice Hall Elements and Compounds > Slide 3 of 25 Distinguishing Elements and Compounds How are elements and compounds different? 2.3 3

4. Slide 4 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds Distinguishing Elements and Compounds An element is the simplest form of matter that has a unique set of properties. Example : Na Sodium A compound is a substance that contains two or more elements chemically combined in a fixed proportion. C+ O 2 ----  CO 2 2.3

5. © Copyright Pearson Prentice Hall Slide 5 of 25 Elements and Compounds > Distinguishing Elements and Compounds Compounds can be broken down into simpler substances by chemical means, but elements cannot. 2.3

6. Slide 6 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds Distinguishing Elements and Compounds Breaking Down Compounds A chemical change is a change that produces matter with a different composition than the original matter. When table sugar is heated, it goes through a series of chemical changes. 2.3

7. Slide 7 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds Distinguishing Elements and Compounds The final products of these chemical changes are solid carbon and water vapor. The following diagram summarizes the process. 2.3

8. Slide 8 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds Problem Classify each of the following as a chemical or physical change. a.Breaking a pencil b.Water freezing and forming ice c. frying an egg d.Burning wood e.Leaves turning color in the fall.

9. Slide 9 of 25 © Copyright Pearson Prentice Hall Elements and Compounds > Distinguishing Elements and Compounds Properties of Compounds In general, the properties of compounds are quite different from those of their component elements. When the elements sodium and chlorine combine chemically to form sodium chloride, there is a change in composition and a change in properties. 2.3

10. Slide 10 of 25 © Copyright Pearson Prentice Hall Elements and Compounds > Problem Classify each of following as a physical or a chemical property a.Aluminium has a silvery color b.Gold has a density of 19 g/cm3 c.Sodium ignites when dropped in water d.Water boils at 100 C e.Silver tarnishes

11. Slide 11 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds Distinguishing Elements and Compounds Chlorine is used to kill harmful organisms in swimming pools. 2.3

12. Slide 12 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds Distinguishing Elements and Compounds Sodium is stored under oil to keep it from reacting with oxygen or water vapor in the air. Sodium vapor produces the light in some street lamps. 2.3

13. Slide 13 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds Distinguishing Elements and Compounds Sodium Chloride (commonly known as table salt) is used to season or preserve food. 2.3

14. © Copyright Pearson Prentice Hall Elements and Compounds > Slide 14 of 25 Distinguishing Substances and Mixtures 2.3 Distinguishing Substances and Mixtures How can substances and mixtures be distinguished?

15. © Copyright Pearson Prentice Hall Slide 15 of 25 Elements and Compounds > Distinguishing Substances and Mixtures 2.3 If the composition of a material is fixed, the material is a substance. If the composition of a material may vary, the material is a mixture.

16. © Copyright Pearson Prentice Hall Slide 16 of 25 Elements and Compounds > Distinguishing Substances and Mixtures This flowchart summarizes the process for classifying matter. 2.3

17. © Copyright Pearson Prentice Hall Slide 17 of 25

18. © Copyright Pearson Prentice Hall Slide 18 of 25

19. © Copyright Pearson Prentice Hall Slide 19 of 25

20. © Copyright Pearson Prentice Hall Slide 20 of 25 Practice Problems for Conceptual Problem 2.2 Problem Solving 2.19 Solve Problem 19 with the help of an interactive guided tutorial

21. © Copyright Pearson Prentice Hall Elements and Compounds > Slide 21 of 25 Symbols and Formulas What do chemists use to represent elements and compounds? 2.3 3

22. © Copyright Pearson Prentice Hall Slide 22 of 25 Elements and Compounds > Symbols and Formulas Chemists use chemical symbols to represent elements, and chemical formulas to represent compounds. These chemical symbols were used in earlier centuries. 2.3

23. Slide 23 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds Symbols and Formulas Each element is represented by a one or two- letter chemical symbol. 2.3

24. Slide 24 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds Element symbols to Memorize Atomic numbers 1-30, 34-38, 47, 50, 53, 55- 56, 79, 80, 82, 83, 86, Know the name and symbol. The name must be spelled correctly

25. © Copyright Pearson Prentice Hall Slide 25 of 25 Section Quiz -or- Continue to: Launch: Assess students’ understanding of the concepts in Section 2.3 Section Quiz. 2.3.

26. © Copyright Pearson Prentice Hall Slide 26 of 25 2.3 Section Quiz 1.Passing an electric current through a certain substance produces oxygen and sulfur. This substance cannot be a(n) a.compound. b.mixture. c.element. d.solution.

27. © Copyright Pearson Prentice Hall Slide 27 of 25 2.3 Section Quiz 2.Which of the following is a mixture? a.sodium chloride b.carbon dioxide c.sucrose d.air

28. © Copyright Pearson Prentice Hall Slide 28 of 25 2.3 Section Quiz. 3.The symbol for the element potassium is a.K. b.Po. c.P. d.Pt.

29. END OF SHOW