1. Lab: Investigating the pH of Substances
Purpose is to determine the pH of common household substances and use this information to identify the substance as an acidic, basic or neutral solution.

2. Water in a Glass How do the Molecules appear?
Diagram below shows
Water molecules with 2 hydrogen
Atoms and 1 oxygen atom
Above is a diagram of the way in water molecules can look in the glass to the left. The water molecules breaks into ions, hydroxide and hydrogen.

3. Vocabulary Building: be sure that you can define these terms to help with the lab
Solvent Solute Solution Aqueous Dissociate Hydrogen ion Hydroxide ion Neutral Solution Acidic Solution Basic Solution
What will you need?

4. Need an “indicator” which is something that detects the presence of a certain substance
pH paper - indicates the presence and amount of H+
add solution to test paper
look for color change – What does it mean?
pH of Acid
pH of Base
pH of Neutral

5. Set up for the Lab
Test tubes contain various household substances

6. An organized work area
Above you can see the three types of papers. The pH paper is the light yellow colored
paper. The red paper is red and the blue paper is blue. A beaker of distilled water is available to clean the stirring rod after each application of a substance on the paper. Preventing contamination of solutions is very important.

7. Analyze… What title would you give to the table below? Solution Litmus
Red
Blue
pH #
Acid
Base
Neutral
Seltzer Water 6
Yes No
Vinegar
1-2
Cranberry Juice 2
Ammonia
9-11
Orange Juice
4-5
Dish soap Water
7-8
Lime or Grape Juice 5
Yogurt
5-6
Analyze…
1. Which has the greatest number of H+ ions? Support.
2. Which has the smallest number of H+ ions? Support
3. Which must have the greatest number of OH- ions? Support
4. Were any solutions neutral? Support.
5. Examine the data for cranberry juice. Does the litmus paper data support the pH paper?
6. Create a pH scale (timeline) and then place each solution on the scale in the correct spot.

8. Use this slide to help you compare the makeup of two solutions
1. In terms of H+ ions, how does a pH of 3 and a pH of 5 compare ?
2. In terms of H+ ions, how does a pH of 8 and a pH of 12 compare?
3. Does a neutral liquid have hydrogen ions?
4. Does a pH of 9 have hydrogen ions?
5. Understanding the concept of pH, identify the strength (strongest to weakest) of each acid solution tested during lab.
Rule: As you move from right to left, the number of Hydrogen ions decreases.
Each time you move one pH value, it is a 10x increase or decrease

9. Review on Your own…. List two characteristics of an acid.
List two characteristics of a base.
Describe a neutral solution.
How do the number of hydrogen ions compare with the orange juice and ammonia?
Which solution which was tested during lab, contains a greater amount of hydroxide ions compared to the number of hydrogen ions?
Write a conclusion for the lab investigation. A conclusion must :
State the purpose of the lab
State the findings of the lab
State if the purpose of the lab was met.