M 1 V 1 = M 2 V 2 Where: V 1 = Needed volume of stock solution M 1 = Sucrose concentration of stock solution = 30% V 2 = Desired volume of Beaker 1 solution = 200mL M 2 = Sucrose concentration of Beaker 1 solution = 15% After solving for V 1 , figure out the how much water is needed to bring the total volume in Beaker 1 to 200mL. Record your calculated volume below. mL of water needed = ____100_________ mL of 30% stock sucrose solution needed = _______100______ Part II: Experimental Procedure IMPORTANT: Your two “unknown” liquids should be at room temperature when you pour them into the dialysis bag. 1. Prepare the following five experimental treatments (solutions in dialysis bags). Treatment Band Color 3% sucrose Yellow 15% sucrose Red 30% sucrose Blue Your Choice #1 Green Your Choice #2 White For each treatment, use the graduated cylinder to measure out 5mL of the corresponding solution (from those that you prepared earlier and your two choices of fluid). Pour those 5mL into the prepared dialysis bag with the matching band color. Secure the tops of each bag in the same way that you secured the bottoms of each bag, using the same colored rubber bands for each bag. If you do not have enough tubing, you can skip tying a knot at the top of the bag. Make sure the top is as secure as possible using
BI205: Introductory Biology II Week 4 Lab Page 5 of 9 the folding/rubber band method. Once secure, place the completed treatment tube back into Beaker 2. IMPORTANT: When you secure the tops of the dialysis tubing, be sure to leave empty space above the liquids in the tubes. This provides space for any water that may move into the bag during your experiment! 2. Describe your “unknown” sugar solutions here. For example, you could say, “I dissolved 1 tablespoon (~15 mL) of honey in 100 mL tap water, and poured 5 mL of this into one dialysis bag, and I poured 5 mL of room temperature orange juice into the other dialysis bag.” Description: I poured 5 mL of Arizona green tea into one dialysis bag and 5 mL of sprite into the other dialysis bag. 3. Take a photograph of your experimental set-up (the dialysis bags in the Beaker 2), and insert it here. Photo:
BI205: Introductory Biology II Week 4 Lab Page 6 of 9 4. Measure the weights of your five filled dialysis bags using the digital scale. Record your measurements in the following table Treatment Band Color Weight 3% sucrose Yellow 6.2 g 15% sucrose Red 6.7 g 30% sucrose Blue 5.2 g Your Choice #1 Green 6.2 g Your Choice #2 White 6.0 g 5. Transfer your five filled dialysis bags to Beaker 1, containing your preparation of 200 mL of 15% sucrose solution. You may pour out some of this solution into a waste beaker if Beaker 1 begins to overflow when you add the dialysis bags. 6. Allow the bags to sit for one hour.
BI205: Introductory Biology II Week 4 Lab Page 7 of 9 7. Using the examples provided in the “BI20x Hypotheses & Predictions Guide” available in Canvas, develop a hypothesis for your experiment. Include your hypothesis, along with supporting scientific reasoning in the space below.
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