Beverage Density Lab Sugar Content Analysis (Due Nov. 11)

Transcription

1 Beverage Density Lab Sugar Content Analysis (Due Nov. 11) Introduction: Nutritionists have recently raised concerns about the increasing popularity of sodas, fruit drinks and other beverages dur to their high sugar content. So, how well do you know the beverages you drink? Try to rank the following four beverages from lowest sugar content to highest: Coke(Classic), Welch s 100% Grape Juice, Powerade, Orange Soda. Along with adding Calories to a beverage, dissolved sugar also increases the density of the solution. In this lab, you will first determine the density of five known solutions: 0%(which is just plain water), 5%, 10%, 15%, and 20% sugar. You will plot these densities on a density vs. sugar content graph. Finally, you will determine the densities of the four beverages, then use the graph to approximate their sugar contents. The density of a solution depends on its concentration, that is how much solute(solid) is dissolved in the solvent (liquid). If the density of a soltuion is plotted on a graph against the concentration of solute, a regular pattern is evident, density is proportional to concentration. The resulting graph is called a calibration curve, shows a straight line relationship between the density of a solution and the concentration of a solute. A calibration curve can be used to determine the concentration of solute in an unknown solution whose density has been measured. The purpose of this lab is to measure the densities of popular beverages and determine their sugar contents using a calibration curve obtained by plotting the densities for a series of reference solutions versus percent sugar. This handout serves as your lab report, no additional formal write up is required. As a result this has to be done in a neat fashion. Hypothesis: Write your hypothesis below. Materials & Equipment: Small cup, balance, pipet, paper towel Procedures: 1. Place a small beaker on the balance and hit the tare (re-zero) button. The scale should read 0.00g. 2. Using pipet draw up precisely 10.00ml of 0% sugar solution into the pipet. Then empty it into the cup, touching the tip of the pipet to the inside wall of the beaker to help get out most of the liquid in the tip. DO NOT TRY TO SHAKE OUT ANY LIQUID THAT REMAINS THERE. The pipets are designed to deliver 10.00ml and that remaining drop should not be squeezed out. Since the beaker has already been zeroed out, the mass is that of the liquid alone. Record this mass reading in the data table in the Observed Data section. Then push the tare/zero button to re-zero the balance for the next reading. 3. Touch the pipet to a paper towel to get rid of the excess liquid in the tip and rinse tip with a water bottle. 1

2 4. Repeat step 2 and 3 with each of the remaining sugar solutions and with each of the four beverages. DO NOT PUT ANY OF THESE SOLUTIONS BACK INTO THE CUPS FROM WHICH THEY CAME. Just leave all liquids in the beaker. If the beaker gets full, simply empty it into the sink, set it back on the balance and push the tare/zero button to continue. 5. Clean up by rinsing all glassware in the sink and throw the paper cup away. Observed Data: SAMPLE DATA Sample Mass(g) Volume(mL) Density (g/ml) 0% % % % % Coke Grape juice Powerade Orange juice (DO AFTER GRAPH) % sugar: coke grape juice powerade orange juice Organized Data: A. Calculations: 1. Calculate the density of each solution. SHOW ALL WORK AND THE ANSWERS IN THIS AREA. 2

3 B. Graph: 1. Carefully plot your calculated densities vs. sugar content(%) for each of the five known solutions. Follow the graphing reference page you received earlier this semester. a. Label your axises. Don t forget units (y-density, x-%) b. Be sure your graph takes up an entire piece of graph paper. c. Use a ruler to draw a best fit straight line through the points. 2. Next, use your graph to approximate the four beverage s sugar content. To do this, start on the y-axis at a density of one of the beverages, then follow the density value over to where it hits the best fit line you drew on your graph. Then go straight down to the x-axis to determine the corresponding sugar content value. Mark and label it on your graph where your beverage densities hit the best fit line. As with any measurement, read your graph as accurately as possible. C. Questions: 1. Explain why you were told not to put solutions back into the containers from which they came. 2. Why was it okay to leave the liquid in the beaker from one trial to the next? 3. In this lab, you discarded all of the solutions into the sink. Can you think of a situation where this would not be appropriate? Explain. 4. Water has a density of 1.00 g/ml at 4 o C. Was your room-temperature value for the density of water(0% sugar) higher or lower then 1.00? Explain why you think your value differs in the direction it did from 1.00g/ml. 3

4 5. This lab focuses on sugar content. What assumption does this lab make concerning all the other ingredients in each of the beverages? Explain. 6. What were your sugar content values for the four beverages? Do these results prove or disprove you hypothesis? Application Questions % sugar = mass of sugar x 100 total mass of beverage 7. If you were going to make g of 10% by mass sugar solution, how many grams of sugar would you have to measure out? How many grams of water? Show your work. 4

5 VI. Conclusion: 1. State whether or not your hypothesis was correct. Support your statement above with data from your lab VII. Sources of Error: 1. According to a coke can label, 1 can of coke (355mL) contains 39 grams of sugar. The density of coke is 1.044g/mL. What percentage of sugar by mass is in this can? SHOW WORK BELOW. 2. Calculate the percent error in the experimental results for sugar content in the Coke using the following equation: Show all set up and answers. % error = experimental - calculated(from#1) x 100 Calculated(from #1) 3. List possible/actual errors and explain the cause of each possible/actual error. 5