1. The pH Scale

2. Remember the household products lab?
You tested household chemicals with litmus paper and pH paper.
Product
Color pH
Formula
Acid/Base? 1. 2. … 9.

3. What happened to the pH paper?
pH paper (aka Universal Indicator Paper)
What color(s) do/does the paper turn for acids?
What color(s) do/does the paper turn for bases?
Reds and oranges
Greens and Blues

4. What is the pH scale?
pH (potential hydrogen) is another way of representing the hydrogen ion (H+) concentration of a solution
pH values range from

5. The pH scale Acidic solution: pH < 7.0 Neutral solution: pH = 7.0
Basic solution: pH > 7.0
Neutral
ACIDIC
BASIC
pH =
Increasing acidity
Increasing basicity

6. The pH Scale

7. How can you tell the pH of a chemical?
Indicators!!!
Indicator paper (like pH paper)
Liquid indicators (like phenolphthalein)
pH meters

8. DEMO
Why do chemistry teachers like to teach about hydroxides?

9. The pH range varies for different indicators
Indicator: a chemical or solution that changes color at a certain pH
The pH range varies for different indicators
Titration Xample

10. Indicator Lab
Many naturally colored compounds can behave as acid-base indicators. In this lab, you will be given a choice of several different fruits and vegetables. Your goal is to make indicator solutions from these fruits and vegetables. Do the following:
Provide a complete set of instructions for making the indicator solution from the raw materials. (Hint: The indicator is usually located in the skin of the fruit or veggie. You will have to boil most of the fruits/veggies in a small amount of water.)
Demonstrate that your indicator solution works for distinguishing between acids and bases.
Create a data table listing your results for 3 indicator solutions. Your table should include (at a minimum) the indicator name and colors observed for pH = 1, 3, 5, 7, 9, 11.
Use the rubric as a guide!
Available Materials: solutions with various pH, carrots, blueberries, red cabbage, red grapes, apples, red onions, and tea leaves. 100mL beaker, deionized water, pipettes, well plates, scoopula.