1. Acid/Base pH Lab What microorganisms do we study in microbiology?
What is one of the ultimate goals of microbiology?
So, why do you think we are studying acids and bases in microbiology?

2. Acids and Bases Acids : Have more hydronium ions Have a sour taste
In concentrated forms can be very corrosive
Example:
Strong acid – HCl (hydrochloric acid)
Weak acid – CH3COOH (vinegar)

3. Acids and Bases Bases : Have more hydroxide ions Have a bitter taste
Tend to feel slippery because they react with the oil on our skin to form soap
Example:
Strong base – NaOH (sodium hydroxide)
Weak base – NH4 (ammonia)

4. Acids and Bases pH scale ranges from 0 – 14:
Solution with a pH of 0 is very acidic
Solution with a pH of 14 is very basic
Solution with a pH of 7 is neutral
pH can be measured with litmus paper or pH strips

5. Procedure Part A
We will be checking the pH of 6 different solutions (there are 6 stations with 1 solution at each station)
Before you start, predict what you think the pH of each solution will be (acidic, basic, neutral)
Then test each solution with red litmus paper – if it turns blue, it is a base
Next test each solution with blue litmus paper – if it turns red, it is an acid
If the solution doesn’t change the color of either type of litmus paper, it is neutral
Finally, test each solution with a pH test strip – compare the strip to the box and get a pH reading!

8. Procedure Part B
We will now be checking the pH of dilute hydrochloric acid (HCl), dilute sodium hydroxide (NaOH), and a mixture of the two – 5 drops of each in test tube (HCl + NaOH = H20 = NaCl).
Before you start, predict what you think the pH of each solution will be (acidic, basic, neutral)
Then test each solution with red litmus paper – if it turns blue, it is a base
Next test each solution with blue litmus paper – if it turns red, it is an acid
If the solution doesn’t change the color of either type of litmus paper, it is neutral
Finally, test each solution with a pH test strip – compare the strip to the box and get a pH reading!

9. Procedure Record your results in the data
Answer all questions completely
Check your lab report rubric to ensure you are including everything
Tape or staple lab sheet into your lab book
Lab is due tomorrow (10/9/13)