Beverage Density Lab

Density Lab Activities

Introduction

Nutritionists have recently raised concerns about the increasing popularity of sodas, fruit drinks, and other beverages due

to their high sugar content. Do you know how much sugar is in your favorite beverage?

Concepts

• Density • Solution

• Concentration • Calibration curve

Background

The purpose of this cooperative class activity 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.

The experimentally determined percent sugar for the beverages will be compared against the information provided on their

nutritional labels to evaluate the accuracy of this method.

Hypothesis

How well does the sweet taste of a beverage correlate with the amount of sugar it contains? Based on your memory of their

taste, predict the relative sugar content in the following beverages: cola, grape juice, and sports drink. (Rank the beverages

from 1, highest sugar content, to 3, lowest sugar content.)

Materials

Beverages (at room temperature)* Cups, clear plastic, 8, labeled 0%, 5%, 10%, 15%,

be accomplished by pouring the beverage back and forth from one container into another several times until it stops fizzing.

Safety Precautions

Although the materials in this activity are considered nonhazardous, follow all normal laboratory safety guidelines. Any food-grade

items that have been brought into the lab are considered laboratory chemicals and are for lab use only. Do not taste or ingest any

materials in the laboratory, and do not remove any food items from the lab after use. Wear safety glasses or chemical splash goggles

whenever working with chemicals, heat or glassware in the lab. Wash hands thoroughly with soap and water before leaving the lab.

Procedure

1. Place a small (100-mL) beaker on the balance and hit the “tare” or “rezero” button. The scale should read 0.00 g.

2. Draw up a precisely measured 10.00 mL of 0% sugar solution into a pipet. Then empty it into the beaker, toughing

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 TD (“to deliver”) 10.00 mL 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.

3. Record this mass in the data table below.

4. Push the “tare” button to rezero the scale for the next reading.

5. Touch the pipet to a paper towel to clean out any residual solution.

6. Repeat steps 2–5 with each of the remaining sugar solutions, and then with each of the three beverages. Do not put any

of the solutions back into the cups from which they came, just leave then in the beaker. When the beaker get full, simple

empty it into the sink, set it back on the scale, and push the “tare” button.

7. Calculate and record the density of each beverage sample. Hint: Since the sample volume is always 10.0 mL, the calculation

Data Analysis

1. Plot the known density on the y-axis versus percent sugar on the x-axis for the following sugar reference solutions. Use a

ruler to draw a “best fit” straight line through the data points.

2. Use the graph to estimate the sugar concentration in the beverage: Locate the point on the y-axis that corresponds to the

beverage density. Follow that point on the y-axis across horizontally to where it meets the best-fit straight line through

the data points for the reference solutions. Draw a vertical line from this point on the best-fit line down to the x-axis. The

point where this vertical “line” meets the x-axis corresponds to the percent sugar in the beverage. Estimate and record the

percent sugar for the beverage.

3. Consult the nutritional label for the beverage—it should list the sugar content in grams of sugar per serving size. This value

Percent sugar = 0.114 g sugar per g of beverage × 100% = 11.4%

4. Calculate the percent error in the experimental determination of the sugar content using the following equation.

| Calculated value − Experimental value |

Percent error = ————————————————–— × 100%

Calculated value

5. This lab examines the relationship between the density of a beverage and its sugar content. What assumption is made

concerning the other ingredients in the beverage and their effect on its density? Is this a valid assumption? Why or why

not?

* 15% = 850 g of water, 150 g of sugar, two blue drops

* 20% = 800 g of water, 200 g of sugar, one drop blue, one drop red

*The sugar concentrations are mass percent.

Then cap and shake well until sugar is all dissolved and solutions are homogeneous.

This makes up close to 1000 mL of each solution, more than enough for 5 sections of 24 students each, working in pairs.

The grape juice and powerade can be used as is from the bottles. The carbonated beverages should be “flattened” first. This

should be done by pouring them back and forth several times between two large beakers. If this is not done, the carbonation can

produce bubbles during pipetting and throw off the results. Certainly, any four (or more) beverages can be substituted in. It is

wise to pick ones with somewhat different sugar contents (see labels), and with somewhat different colors.

Disposal

friendly competition to determine the results of the testing. Try to obtain a variety of non-diet beverages.

• Fructose (“fruit sugar”) is the main sugar present in fruit juices, fruit drinks such as Snapple,

®

and most carbonated sodas.

For best results, the beverage samples should be at room temperature, as close to 20 °C as possible.

• Table sugar is sucrose, a disaccharide composed of one molecule of fructose joined with one molecule of glucose after

loss of water. Both fructose and sucrose reference solutions were tested in this activity and both gave similar results and

accuracy.

• Sports drinks such as Gatorade

®

are the “exception that proves the rule” in this study. The working assumption in this

experiment is that sugar is the main ingredient whose concentration determines the beverage density. This assumption

Sample Results

9.98 10.18 10.38 10.59 10.81 10.4 10.6 10.3