What effect does dilution of an acid or base have on the pH of the solution?

1. What effect does dilution of an acid or base have on the pH of the solution? https://phet.colorado.edu/sims/html/ph-scale/latest/ph-scale_en.html

2. What effect does dilution of an acid or base have on the pH of the solution? On page 4 of your notebook, write predictions in complete sentences… • Will the pH of an acid increase, decrease, or remain the same if you add water to it? • Will the pH of a base increase, decrease, or remain the same if you add water to it? • Will the pH of water increase, decrease, or remain the same if you add water to it?

3. What effect does dilution of an acid or base have on the pH of the solution? Play around with the sim a little to see how it works. Watch the video introduction to the sim HERE. Come up with a procedure to answer the research question: “What effect does dilution of an acid or base have on the pH of the solution?” Use these guiding questions in your investigation. Write responses to these questions on page 4 of your notebook. Use complete sentences. • What is the pH of water? • Can you turn an acidic solution basic by diluting the solution? • Can you turn a basic solution acidic by diluting the solution? • When an acid or base is diluted, what pH value does it move towards? • What effect does dilution of an acid have on the pH of the solution? • What effect does dilution of a base have on the pH of the solution?

4. What effect does dilution of an acid or base have on the pH of the solution? Please answer these questions on page 4 of your notebook • What did you learn from this exercise? • What effect does dilution of an acid or base have on the pH of the solution? • Review your predictions from earlier… Were you right or wrong with any of your predictions?

5. On the molecular level, what is the difference between acids and bases? Do this investigation on page 5 of your notebook.

6. On the molecular level, what is the difference between acids and bases? Use THIS sim (click on “Micro”). Watch THIS video to get an overview of the activity. Create a table in your notebook like the one below… Make enough rows to test 4 chemicals and 4 dilutions:

7. On the molecular level, what is the difference between acids and bases? • Choose 1 chemical (coffee, for example). • Write down the pH, the [H3O+] and the [OH-]... Remember: [brackets] represent “concentration.” • Multiply those numbers together. Write down your data. • Make a dilute solution of your chemical. Repeat steps 2 and 3. • Repeat this process for a total of 4 different chemicals and their dilutions.

8. On the molecular level, what is the difference between acids and bases? Answer these prompts: • Describe the difference between an acid and a base on the molecular level. • What is the product of [H3O+] x [OH-] • What happens to pH as [H3O+] increases? Decreases? • What happens to pH as [OH-] increases? Decreases? • Add a ninth row to your table… Repeat the process for pure water.

9. On the molecular level, what is the difference between acids and bases? Example

10. pH Scale: qualitative learning goals Determine if a solution is acidic or basic using pH b) H3O+/OH- ratio molecular size representation c) Hydronium/Hydroxide concentration Relate liquid color to pH. Predict if dilution and volume will increase, decrease or not change the pH Organize a list of liquids in terms of acid or base strength in relative order with supporting evidence.  Write the water equilibrium expression. Describe how the water equilibrium varies with pH.

11. 1. The color of a solution identifies if it is an acid, base, or neutral solution. • True B. False C. red is acid & clear is base

12. 2. Which solution is basic? A B C D. More than one E. None

13. 3. Which solution is acidic? A B C D. More than one E. Difficult to tell

14. 4. Which solution is basic? A B C D. More than one E. None

15. 5. Which solution is acidic? A B C D. More than one E. None

16. 6. How will adding water effect the pH? • Increase the pH • Decrease the pH • No pH change

17. A: more water lessens the acidity, so pH goes up

18. 7. How will equal amount of water effect the pH? • Increase the pH • Decrease the pH • The pH will be cut in half • No pH change

19. B: more water lessens the basicity , so pH goes down, from 10 to 9.7, but not by 2 (log scale)

20. 8. What is the order from most acidic to most basic? A B C A B C A C B B A C C B A C A B

21. 9. What is the order from most acidic to most basic? A B C A B C A C B B A C C B A C A B

22. 10. If spit has a pH = 7.4, what does that tell you about the water equilibrium?2H2O  OH- + H3O+ Something was added that made the equilibrium shift left Something was added that made the equilibrium shift right pH has nothing to do with the water equilibrium

23. Answer to 10Since the pH is not 7, then something was added to make the equilibrium shift left. For example, if NaOH was added to water, OH- is immediately in the solution and some of it will react with the H3O+ , so the pH (which is inversely related to [H3O+ ]), goes up. If something like HCl were added there would be more H3O+ , which would also cause a shift left, but there would be less OH- , (which is directly related to pH), so the pH is less than 7.