Toxins Unit – Investigation IV

1. Toxins Unit – Investigation IV Lesson 1: Heartburn

2. ChemCatalyst • Countless products are advertised on TV with the promise of reducing acid indigestion. • What is acid indigestion? What is acidity? • What does acid have to do with your stomach? • How do you think acid “reducers” work? Unit IV • Investigation IV-X

3. The Big Question • What are some characteristics of solutions that are acidic, basic, or neutral? Unit IV • Investigation IV-X

4. You will be able to: • Describe the differences among acidic, basic, and neutral solutions. Unit IV • Investigation IV-X

5. Notes • Indicators: A set of substances that respond to other substances with vivid color changes. Unit IV • Investigation IV-X

6. Activity • Purpose: This activity will introduce you to a special category of solution. (cont.) Unit IV • Investigation IV-X

7. (cont.) • Safety note: Do not get acids and bases on your skin. In case of a spill, rinse with large amounts of water. Wear goggles. (cont.) Unit IV • Investigation IV-X

8. Unit IV • Investigation IV-X

9. 0 7 14 (cont.) (cont.) Unit IV • Investigation IV-X

10. (cont.) Unit IV • Investigation IV-X

11. Making Sense • Look for patterns in the names, chemical formulas, uses, and properties of the substances you tested. • List four characteristics of acids. • List four characteristics of bases. Unit IV • Investigation IV-X

12. Notes • Indicators can be used to identify substances that are acidic, basic, and neutral when dissolved in water. • Acids turn cabbage juice pink and are between 0 and 7 on the universal indicator scale. • Bases turn cabbage juice green or blue and are between 7 and 14 on the universal indicator scale. • Neutral substances do not change color with cabbage juice and are at or very near 7 on the universal indicator scale. (cont.) Unit IV • Investigation IV-X

13. (cont.) • pH scale: A number line from 0 to 14. The numbers are associated with indicator colors. • The numbers associated with indicator colors are also called pH numbers or simply pH. Unit IV • Investigation IV-X

14. Check-In • An unknown substance is purple with cabbage juice and does not react with calcium carbonate. Is it an acid, base or neutral substance? Explain. Unit IV • Investigation IV-X

15. Wrap-Up • Acids and bases are different types of solutions and are classified according to their observable behavior. • Acids and bases respond differently to indicators. Depending on the indicator, different colors will form that show either an acidic or basic substance. Unit IV • Investigation IV-X

16. Toxins Unit – Investigation IV Lesson 2: Watered Down

17. ChemCatalyst • Describe what you observe in the three vials. • What is one explanation for the differences you observe? • If you tested each solution with universal indicator before putting in the gummy bears, what colors would you expect to see? Unit IV • Investigation IV-X

18. The Big Question • How does dilution affect the acidity or basicity of a solution? Unit IV • Investigation IV-X

19. You will be able to: • Explain how dilution affects the concentration and pH of a solution. Unit IV • Investigation IV-X

20. Activity • Purpose: In this activity you will examine the effect of concentration on acidity and basicity of solutions. (cont.) Unit IV • Investigation IV-X

21. (cont.) • Safety note – Do not get acids and bases on your skin. In case of a spill, rinse with large amounts of water. Wear goggles. (cont.) Unit IV • Investigation IV-X

22. Data Table for dilution of 1.0 M HCl Unit IV • Investigation IV-X

23. Data Table for dilution of 1.0 M NaOH Unit IV • Investigation IV-X

24. Data Table for dilution of 1.0 M NaCl Unit IV • Investigation IV-X

25. Making Sense • What does concentration have to do with the acidity or basicity of a solution? Unit IV • Investigation IV-X

26. 0 7 14 Notes More H+ More OH– pH scale (cont.) Unit IV • Investigation IV-X

27. (cont.) • Arrhenius definition: • An acid is any substance that adds a hydrogen ion (H+) to the solution. • A base is any substance that adds a hydroxide ion (OH–) to the solution. (cont.) Unit IV • Investigation IV-X

28. (cont.) • HA  H+ + A– • XOH  X+ + OH– Unit IV • Investigation IV-X

29. Check-In • Lemon juice has a pH of about 2. What does this tell you about what is in the solution? • What would happen if you diluted this solution? Unit IV • Investigation IV-X

30. Wrap-Up • The acidity and basicity of a solution are related to the concentration of the solution. Dilute solutions are less acidic and basic than more concentrated solutions. • Dilution of an acid or a base results in a solution that is increasingly neutral. (cont.) Unit IV • Investigation IV-X

31. The pH scale is related to the concentration of H+ and OH– ions in solution. • According to Arrhenius, an acid is any substance that adds a hydrogen ion (H+) to the solution and a base is any substance that adds a hydroxide ion (OH–) to the solution. Unit IV • Investigation IV-X

32. Toxins Unit – Investigation IV Lesson 3: pHooey!

33. ChemCatalyst • Examine the following data: (cont.) Unit IV • Investigation IV-X

34. (cont.) • What do you think pH really represents? • How does the concentration of the solutions relate mathematically to the pH of the solutions? Unit IV • Investigation IV-X

35. The Big Question • How does pH relate to the concentrations of acidic and basic solutions? Unit IV • Investigation IV-X

36. You will be able to: • Find the pH of a solution if you know the concentrations of hydrogen or hydroxide ions that it contains. Unit IV • Investigation IV-X

37. Activity • Purpose: You will explore the relationship between pH, pOH, [H+], and [OH–]. (cont.) Unit IV • Investigation IV-X

38. Unit IV • Investigation IV-X

39. HCl Unit IV • Investigation IV-X

40. NaOH Unit IV • Investigation IV-X

41. Making Sense • How are pH and pOH related to each other mathematically? Unit IV • Investigation IV-X

42. Notes pH = 4 pH = 5 pH = 6 pH = 7 This box would show 1,000 H+ ions and 1,000 Cl– ions. This box would show 100 H+ ions and 100 Cl– ions. (cont.) Key: H+ Cl– Unit IV • Investigation IV-X

43. (cont.) • pH = –log[H+] • pOH = –log[OH–] (cont.) Unit IV • Investigation IV-X

44. (cont.) • Sample Problem: • What is the pH of a solution with a hydrogen ion concentration of 3.4  10–4 moles/ L? (cont.) Unit IV • Investigation IV-X

45. (cont.) • Please be careful when entering scientific notation into your calculator—it is very easy to make a mistake. When entering 3.4  10–4, first enter “3.4”. Then press the button labeled “EXP” or “10X” or “EE”. Now enter –4, using the “+/–“ key, not the subtraction key. Never try to enter this number by pressing “X” and “10” and “–4”. Unit IV • Investigation IV-X

46. Check-In • What is the pH of a solution with [OH–] = 1.0  10–12 M? Unit IV • Investigation IV-X

47. Wrap-Up • The relationship between pH and pOH of a solution is expressed by the following: pH + pOH = 14. • The relationship between [H+] and [OH–] in a solution is expressed by the following: –log [H+] + –log [OH–] = 14. • The pH of a solution is logarithmically related to the concentration of hydrogen ion and can be calculated mathematically using the following equation: pH = log [H+] Unit IV • Investigation IV-X