SAFETY GOGGLES MUST BE WORN AT ALL TIMES!

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1 SUGAR ME UP, DUDE! PURPOSE: To determine the density of five sugar reference solutions To determine the density of your two beverages, using the references as a guide To graph density versus percent sucrose for your sugar solutions, and understand various aspects of graphing To calculate percent error in order to determine your uncertainty in measurement BACKGROUND INFORMATION: Have you ever been to the ocean? Does it seem that you can float or swim much easier in the ocean than in a swimming pool? Seawater is denser than freshwater due to the presence of dissolved salt in the ocean. As a result, our buoyancy ability to float is greater in salt water than in plain water. Have you ever tried to take a regular soda and float it in water? How about a diet soda? What happens? What factors determine the density of a solution? Can the density of a solution be used to determine how much of a particular substance is dissolved in it? MATERIALS USED: Distilled Water Two Beverages of Choice Digital balance 140 ml Beaker 10 ml Pipette Pipetter Your Brain Sugar reference solutions 25 ml of each (0%, 5%, 10%, 15%, 20%) SAFETY GOGGLES MUST BE WORN AT ALL TIMES! PROCEDURE - PART A: 1. Make sure you have 6 sigma bottles at your station marked 0%, 5%, 10%, 15%, 20%, and distilled H 2 O rinse, that they are filled with sugar solutions and distilled H 2 O. 2. Place an empty 140 ml beaker in the balance and hit the tare button. The balance should read 0.00g, as if there is nothing on the balance at all. 3. Draw up ml of the 0% sugar solution (distilled water duh!) into a pipette and transfer the liquid to the empty beaker. 4. Record the mass of the solution in Data Table A. Remember what the balance is giving you is now just the mass of the solution, with out the beaker! 5. Dispose of the solution into the sink. Rinse the beaker and pipette with distilled water, and repeat steps 1-4 for each of your four sugar reference solutions. Make sure you rezero the balance before each new mass measurement! 6. Calculate the density of each solution and record in Data Table A. Include these calculations on a separate sheet of paper! Hint: Since the volume is always ml, the calculation should be easy you don t need a calculator!

2 PROCEDURE - PART B: 1. Use the procedure from Part A to determine the density of two beverages of your choice. Pour a small sample of your two beverages into two new sigma bottles. Rinse your beaker with distilled water, and record all mass and volume data in Data Table B. Make sure that you rinse your pipette and beaker each time, especially between the two beverages. DATA: DATA TABLE A: DENSITY OF REFERENCE SOLUTIONS Solution Mass (g) Volume (ml) Density (g/ml) 0% sugar 5% sugar 10% sugar 15% sugar 20% sugar DATA TABLE B: BEVERAGE DENSITIES Beverage Mass (g) Volume (ml) Density (g/ml) RESULTS DATA TABLE: BEVERAGE DENSITIES AND CALCULATED % SUGAR CONCENTRATION Beverage Density (g/ml) % Sugar Concentration GRAPHS/DATA TABLES: 1. Plot density versus concentration for the five reference solutions on a graph. The concentration is the independent variable, and the density is the dependent variable. Do you know where those go on a graph? Ask yourself what independent and dependent mean. After the points are graphed, you want to connect them with a line of best fit. This is a line that connects as many points as possible together because they share a relationship. You may graph with Logger Pro it has this feature, and will do it automatically. It is referred to as a linear fit. It is under the analyze option on the menu, and is also a separate button on the button bar.

3 2. Using the information provided to you by your graph, write an equation for the line on your graph. You will use this equation to solve for your unknown soda concentration. Use this equation to do the calculation in #3 below. ATTACH THE GRAPH TO YOUR LAB REPORT! CALCULATIONS: (use full units, and include all calculations on A SEPARATE SHEET OF PAPER!) 1. Show the calculations that you did above for the density of each sugar sample, and for your two soda samples. All calculations need to be included on a separate calculations page, with each section numbered and labeled. 2. Calculate the actual accepted value of the sugar concentration for both of your beverages, using the nutritional information and your measured density value. Record both the nutritional information and the actual percent sugar concentration on your calculations page and label them. 3. Calculate the unknown concentration of both of your beverages using the equation for your line, y = mx +b. Use this concentration to figure out the percent error below. 4. Use the following equation to calculate the percent error for sugar content for both of your beverages. Enter the percent errors for both beverages in your Results Data Table. % ERROR = MEASURED VALUE ACCEPTED VALUE X 100% ACCEPTED VALUE CONCLUSION QUESTIONS: 1. What was your measured density for pure water (0% sugar solution)? The density of water is quoted as 1.00 g/ml, but this precise value is for 4 0 C. Comment on why your measured density might be higher or lower than this. 2. This lab looks at 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 the density of the solution? Do you think this a valid assumption? Explain.

4 3. a. When plotting data such as that obtained in this experiment, why is it not appropriate to connect the dots? b. What type of connection did we draw between the points plotted on the graph? c. Why do all of the points not fall on a straight line together? d. Comment on the sources of error in this experiment and their likely effect on the results. e. What is the benefit in being able to interpolate other unknown values from a line of best fit? 4. The main ingredient in soda, besides water, is obviously sugar. Look at your densities for each sugar solution, and each beverage. a. Are your beverages and solutions more or less dense than water? b. What would happen if you were to take a full can of regular soda and place it into a bucket of water? c. Hypothesize as to why a can of diet soda will float! 5. Let s say that an unknown beverage has a density of 1.03 g/ml. Calculate its % concentration using your equation from your graph below.

5 PRE-LAB QUESTIONS 1. If the following mass and volume data are used to calculate the density of a solution, how many significant figures are allowed in the calculated density? Mass of solution grams, volume of solution 8.27 ml. 2. Calculate the density of the solution described in Question #1. 3. According to its nutritional label, orange soda contains 49 grams of sugar per 355 ml serving. If the density of the beverage is /ml, what is the percent sugar concentration in orange soda? Hint this is a two-step problem! First, use the density to convert the 355 ml of soda to grams. Then, calculate the percent sugar in the soda.