1. What we are doing NOW… Turning in, stapled and IN ORDER:
Lab #2: The Scientific Method
Pre-Lab exercise (41 & 42), LAB QUESTIONS (49-51)
Sticker for completed work but NOT to tear
out:
Lab #3: Investigations into Properties of Solution pH and Conductivity
Pre-Lab exercise (62-65)

2. Due NEXT CLASS: Tuesday, March 3 Thursday, February 26
Lab #3: Investigations into Properties of Solution
pH and Conductivity
Pre-Lab exercise (62-65)
LAB EXCERISES with REVIEW QUESTIONS (66-68)
Lab #4: What’s in Our Food?
Pre-Lab exercise to check for completion (75-77)
Tuesday, March 3
503
501
550
Thursday, February 26
502
Friday, February 27
506
551

3. HEADS UP for Extra Credit opportunity
Article and summary about nutrition OR
My Food Plan (with synopsis)
Due in TWO weeks

4. Part I: Testing the pH of diluted acid
Make a serial dilution of 0.1 M HCl.
What is the independent variable you have created?
The dependent variable?
What is being held constant?
1 mL
1 mL
1 mL
1 mL
1 mL
.1M HCl A B C D E
pH 0 A
pH 1
pH 2
pH 3
pH 4
pH 5
9 mL
of H2O
9 mL
of H2O
9 mL
of H2O
9 mL
of H2O
9 mL
of H2O

5. Part I: Testing the pH of diluted acid
Once the solutions have been made and you have recorded your predictions, place the pH strips on a paper towel to make the pH observation. Write the solution version above the pH paper. A B C D E

6. Part II: Conductivity Test Particles dissolved = solute
Prepare 0.1 M glucose solution and 0.1M salt solution
Test the conductivity of glucose, salt, acid and base solutions
Particles dissolved = solute
Water = solvent

7. Part II: Solutions, Dilutions!
If you are given: 100mL of a 0.1 M glucose solution…
molar mass* X desired molarity X desired volume in Liters
= number of grams of solute
(C6H12O6 {180g/mol}) X (0.1mol/L) X (.1L) =
__1.8 g___
* Use the periodic chart on page 70

8. Additional Homework: Part II: Solutions, Dilutions!
How do you prepare 100 mL of 0.25 M HCl
from a 6 M acid stock solution?
(C1) (V1) = (C2) (V2)
Additional Homework:
How do you prepare a 100 mL of 0.5 M NaCl solution
from a 3 M salt stock solution?

9. Part III: Testing Buffers Phenol red is a color indicator.
Test Tube 1:
5 mL of water
5 mL of phosphate buffer
? drops of Phenol Red
for change
Test Tube 2:
10 mL of water
? drops of Phenol Red
for change
Phenol red is a color indicator.
At neutral, it is color red, acidic environment = yellow, basic environment = purple.

10. Let’s get to WORK!!! I will demonstrate part III
for you after parts I and II
(so there will be one less lab for you to clean up).
Be sure to CAREFULLY review your procedures, take notes on what occurs, and carefully clean/dry your materials before placing them back in the bin.