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)

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

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

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

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

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

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

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?

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.

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.