Beverage Density Lab Sugar Content Analysis Introduction The

Beverage Density Lab Sugar Content Analysis

Introduction The density of a pure substance is a characteristic physical property that can be used to identify the substance. Density is defined as the ratio of mass per unit volume. It is an “intensive” property; that is, it does not depend on the amount of the substance. The density of any material is determined by measuring its mass and volume and then dividing the mass by the volume. The mass of a substance can be measured directly using a balance. The volume of a liquid can also be measured directly using special laboratory glassware, such as a graduated cylinder, a buret, or a pipet. In this experiment, liquid volumes will be measured using a pipet. A pipet is designed to deliver an accurate and precise volume of liquid to another container.

The density of a solution depends on its concentration, that is, how much solute (solid) is dissolved in the solvent (liquid). The higher the concentration of solute, the greater the density of the solution. A convenient way to express concentration is in units of weight percent, which corresponds to the number of grams of solute that are present in 100 g of solution. A 20% salt solution is prepared by dissolving 20 g of sodium chloride in 80 g of water. (Notice that the final mass of the solution is 100 grams. ) If the density of a solution is plotted on a graph against the concentration of solute, a regular pattern is evident. Density is directly proportional to concentration. A 20% salt solution, for example, has a greater density than a 10% salt solution. If the densities of several solutions on known concentrations are determined experimentally, a calibration curve (graph) can be constructed that shows a straight-line relationship between the density of a solution and the concentration of solute. The calibration curve can then be used to find the concentration of solute in an unknown solution.

Experiment Overview The purpose of this experiment is to determine the percent sugar content in beverages. The density of five sugar “reference” solutions will be measured in Part A. The reference solutions contain known amounts of sugar (0 -20%) and have been dyed with food coloring to make it easier to tell them apart. 0% sugar 5% sugar 10% sugar 15% sugar 20% sugar = clear = yellow = green = blue = purple Their densities will be plotted on a graph to obtain a calibration curve of density versus percent sugar concentration. In part B, the densities of two beverages will also be determined and the calibration curve used to find how much sugar they contain. The results will be compared against the information provided on the nutrition labels for these beverages.

Pre-Lab Questions 1. If the following mass and volume data are used to calculate the density of solution, how many significant figures are allowed in the calculated density? Mass of solution = 12. 53 g; volume of solution = 8. 27 m. L. 2. Calculate the density of the solution described in Question #1. 3. According to its nutritional label, orange soda contains 49 g of sugar per 355 m. L serving. If the density of the beverage is 1. 043 g/m. L, what is the percent sugar concentration in orange soda? Hint: This is a 2 -step problem. First, use the density to convert the 355 m. L serving size to grams. Then calculate percent sugar in the beverage.

Data Table A: Density of Reference Solutions Solution Mass, g Sample Volume, m. L Density, g/m. L 0% Sugar 9. 95 g 10. 00 0. 995 5% Sugar 10. 14 g 10. 00 1. 014 10% Sugar 10. 34 g 10. 00 1. 034 15% Sugar 10. 53 g 10. 00 1. 053 20% Sugar 10. 73 g 10. 00 1. 073

Density vs. Percent Sucrose Calibration Curve 1. 08 1. 07 Density (g/m. L) 1. 06 1. 05 1. 04 1. 03 1. 02 1. 01 1. 00 0. 99 0 5 10 15 Percent Sucrose 20 25 30

Data Table B: Beverage Densities Beverage Mass, g Sample Volume, m. L Density, g/m. L Powerade 10. 27 g 10. 00 1. 027 Lemon-lime soda 10. 35 g 10. 00 1. 035 Cola 10. 38 g 10. 00 1. 038 Apple juice 10. 42 g 10. 00 1. 042 Grape juice 10. 59 g 10. 00 1. 059

ØThe relevant information on this label is the grams of sugars, NOT the Percent Daily Value. ØThis soda contains 40 g of sugar per 355 m. L of beverage. Nutrition Facts Serving Size: 1 Can (355 m. L) Amounts Per Serving Calories 150 Total Fat 0 g Sodium 55 mg Total Carb. 40 g Sugars 40 g Protein 0 g % Daily Value* 0% 2% 13% 0% * Percent Daily Values are bases on a 2, 000 calorie diet.

from calibration curve Data Table C: Results Table Beverage Measured density, g/m. L Percent sugar (experimental) Amount of sugar (Nutrition label) Percent sugar (calculated from Nutrition label) Percent error Powerade 1. 027 8. 3% 15 g/240 m. L 6. 1% *36% Lemon-lime soda 1. 035 10. 3% 38 g/355 m. L 10% 3% Cola 1. 038 11. 1% 42 g/355 m. L 11% 1% Apple juice 1. 042 12. 1% 38 g/296 m. L 12% 1% Grape juice 1. 059 16. 5% 40 g/240 m. L 16% 3% *Powerade contains a large amount of salt (electrolytes)

Pre-Lab Questions 1. If the following mass and volume data are used to calculate the density of solution, how many significant figures are allowed in the calculated density? Mass of solution = 12. 53 g; volume of solution = 8. 27 m. L. (3 sig. figs. ) (4 sig. figs. ) (3 sig. figs. ) 2. Calculate the density of the solution described in Question #1. Density = mass volume Density = 12. 53 g 8. 27 m. L Density = 1. 52 g/m. L 3. According to its nutritional label, orange soda contains 49 g of sugar per 355 m. L serving. If the density of the beverage is 1. 043 g/m. L, what is the percent sugar concentration in orange soda? Hint: This is a 2 -step problem. First, use the density to convert the 355 m. L serving size to grams. Then calculate percent sugar in the beverage. X g = 355 m. L 1. 043 g = 370 g 1 m. L 49 g x 100% = 13% 370 g

Data Table C: Results Table Beverage Measured density, g/m. L Percent sugar (experimental) Amount of sugar (Nutrition label) Percent sugar (calculated from Nutrition label) Percent error Powerade 1. 027 8. 3% 15 g/240 m. L 6. 1% *36% Lemon-lime soda 1. 035 10. 3% 38 g/355 m. L 10% 3% Cola 1. 038 11. 1% 42 g/355 m. L 11% 1% Apple juice 1. 042 12. 1% 38 g/296 m. L 12% 1% Grape juice 1. 059 16. 5% 40 g/240 m. L 16% 3% DO NOT use volume… need to convert to mass first (using density) X g = 355 m. L 1. 038 g = 338 g 1 m. L 42 g x 100% = 12% 355 m. L 42 g x 100% = 11% 368 g

Printable copy of LAB Teacher Notes • Have students make standard reference samples of 5%, 10%, 15%, 20% sugar • Use balances that have more than 0. 0 g precision • Students should use 10 m. L pipets for references • Teacher may want to set-up buret with beverage samples • Scales not working properly and pipet bulbs that don’t work were largest problem with this lab. • Have students place dirty pipets in bucket of soapy water at end of lab • DO NOT ALLOW students to pour samples back into containers