1. Today we will:

2. Learn about Elements and Compounds.

3. HOMEWORK: Read section 3.4 Answer questions 20-24 on page 76.

4. An element is a pure substance that cannot be broken down by physical or chemical means. Elements and Compounds

5. An element is a pure substance that cannot be broken down by physical or chemical means. Elements and Compounds

6. A compound is two or more elements combined chemically. Elements and Compounds

7. A compound is two or more elements combined chemically. Elements and Compounds

8. Law of definite proportions: Elements and Compounds

9. Law of definite proportions: A compound always has the same elements in the same proportions by mass. Elements and Compounds

10. Law of multiple proportions: Elements and Compounds

11. Law of multiple proportions: Some elements combine in several different proportions, but always in ratios of small whole numbers. Elements and Compounds

12. Sample Problems

13. % = x 100 Sample Problems part whole

14. A 20.0g sample of sucrose contains: 8.44g Carbon 1.30g Hydrogen 10.26g Oxygen What is the percent by mass of each element in the compound? Sample Problems

15. A 20.0g sample of sucrose contains: 8.44g Carbon 1.30g Hydrogen 10.26g Oxygen What is the percent by mass of each element in the compound? Sample Problems

16. 8.44g C Sample Problems 1.30g H 10.26g O

17. 8.44g C 20 g Sample Problems 1.30g H 20 g 10.26g O 20 g

18. 8.44g C 20 g Sample Problems 1.30g H 20 g 10.26g O 20 g x 100 %

19. 8.44g C 20 g Sample Problems 1.30g H 20 g 10.26g O 20 g x 100 % = 42.2 % C x 100 %

20. 8.44g C 20 g Sample Problems 1.30g H 20 g 10.26g O 20 g x 100 % = 42.2 % C x 100 % = 6.5 % H x 100 %

21. 8.44g C 20 g Sample Problems 1.30g H 20 g 10.26g O 20 g x 100 % = 42.2 % C x 100 % = 6.5 % H x 100 % = 51.3 % O

22. 8.44g C 20 g Sample Problems 1.30g H 20 g 10.26g O 20 g x 100 % = 42.2 % C x 100 % = 6.5 % H x 100 % = 51.3 % O

23. 8.44g C 20 g Sample Problems 1.30g H 20 g 10.26g O 20 g x 100 % = 42.2 % C x 100 % = 6.5 % H x 100 % = 51.3 % O 100 %

24. Two unknown compounds are tested. Compound I contains 64.20g of copper and 35.80g of chlorine. Compound II contains 47.27g of copper and 52.73g of chlorine. Are the compounds the same? Sample Problems

25. Two unknown compounds are tested. Compound I contains 64.20g of copper and 35.80g of chlorine. Compound II contains 47.27g of copper and 52.73g of chlorine. Are the compounds the same? Sample Problems

26. 64.20g Cu 35.80g Cl 47.27g Cu 52.73g Cl Sample Problems

27. 64.20g Cu 35.80g Cl 47.27g Cu 52.73g Cl Sample Problems = =

28. 64.20g Cu 35.80g Cl 47.27g Cu 52.73g Cl Sample Problems = 1.793 =

29. 64.20g Cu 35.80g Cl 47.27g Cu 52.73g Cl Sample Problems = 1.793 = 0.8964

30. 64.20g Cu 35.80g Cl 47.27g Cu 52.73g Cl Sample Problems = 1.793 = 0.8964 =

31. 64.20g Cu 35.80g Cl 47.27g Cu 52.73g Cl Sample Problems = 1.793 = 0.8964 = 2

32. HOMEWORK: Read section 3.4 Answer questions 20-24 on page 76.