1. Pre-Lab 19B: Acids, Bases and pH

2. Purpose Life exists inside a certain range of pH values.
A pH value describes whether a solution is acidic, basic (alkaline), or neutral by describing the concentration of hydronium ions in a solution.
An acid is a substance that produces hydronium (H3O+) ions when dissolved in water,
and a base (or alkali) is a substance that produces hydroxide (OH-) ions when dissolved in water.
Neutral solutions have equal numbers of H3O+ and OH- ions.

3. In this investigation, you will learn the pH of several common solutions by making a pH scale using a pH indicator and chemicals of known pH.
You will also identify two ‘mystery’ chemicals (unknowns) with your created pH scale/table.
You will be graded on lab performance and product accuracy/write-up

4. Key Question
What is pH?

5. Background
Define: pH
Acid
Base

6. Drawing
Draw figure from your text book

7. Section1:
Make your pH predictions for the chemicals BEFORE EXPERIMENT!!!!

8. Section 2:
Work in pairs:
To create your pH scale, you will be using solutions 1 to 7 in the table below.
You will be using a 12 holed well plate, per row
Number each of the wells, use pencil !!!!, to correlate to the number of each of the solutions on the data chart
Number 4, red cabbage, is the control
What is a control?

9. Place 3 drops of the cabbage/control into the first 7 labeled wells
Put pipettes back into the correct solutions
What happens when the pipettes are wrongly placed?

10. Section 2B:
Finish the 5 remaining substances using the same procedure as we did in the initial 7 solutions
Use the first 7 solution findings to determine the last 5 solution pH’s
Wash well plates extremely thoroughly, why?
Stack well plates upside-down and perpendicular to each other

11. Post Lab: