AP Kitchen Chemistry Lab #1: Density of Different Dairies
Cooking: What’s in milk? Looking at a few nutrition labels and you will receive a pretty similar sample of
answers: proteins, fat, carbs, and some essential nutrients. So why are there so many different
kinds? The answer is actually pretty simple, and can be analyzed by calculating the density of the
different varieties.
Purpose: Find the density of different dairy products with known concentrations and assess the accuracy of
your results with the literature values. Use experimental and class data to determine the density of
each of the solid and liquid dairy substances being dealt with. To create comparative values,
students will calculate the density of string cheese and marbles. Use correct sig figs on all
measurements and calculation results. Create an excel graph using your data and find the standard
deviation for your data.
Procedure:
Pre-lab:
Prepare a data table that will contain space for all the data and calculation results needed in the
experiment. Check all your lab supplies in your lab drawer to be sure you have everything.
Materials
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Half and Half
Heavy Cream
Whole Milk
2% Milk
Skim Milk
100 mL Graduated Cylinder
Digital Mass Scales
Dixie Cups
Pipet
String Cheese
Marbles
Lab:
1. Each group will be assigned 2 different liquid diary products and a chunk of solid dairy from the
following list: Heavy Cream, Half and Half, Whole Milk, 2% Milk, Skim Milk and String Cheese.
Each group will measure the density of each mixture, before comparing these values to the density of
water and metal marbles.
2. You will begin with the solutions that you were assigned. Choose a volume between 10-15 mL that
is easy for you to measure and gives you 3 sig figs. Use a pipet to add the solution to a graduated
cylinder and measure the volume accurately to the 0.1 mL place. Record this value.
3. Using the digital scale and Dixie cups, first place the Dixie cup on the scale and press the tare/zero
button. Once the weight value shows 0.00 g, pour the first solution into the tared Dixie cup and
record the new mass value. Repeat this step for each of the liquid solutions.
4. Use the mass and volume of each to calculate the density of the respective dairy solutions.
5. Next, use the Dixie cups and digital scale to weigh out the given portion of string cheese. Record the
mass.
6. Grab a graduated cylinder and fill it with water up to the 20 mL line. Place the portion of string
cheese into the graduated cylinder and chart down the final volume. Take the difference of the two to
find the volume of the portion of string cheese.
7. Repeat the trail for the marble. Using the mass and volume collected, calculate the density of both.
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LABS
Results/Discussion:
Analysis: To be answered in your lab notebook.
1. Each group needs to find the other group(s) results to compile a complete list containing the density
of all solutions and other groups’ values for the density of their portion of string cheese. Find the
average of the similar trials that were taken and insert all calculated values into the google
spreadsheet. Copy down the average densities from the other groups into your lab notebook.
2. Use excel to create a graph comparing the dairy solutions to their density with four data points. Use
the graph to help you make an estimate of where light cream would fall on the graph.
3. Determine your group’s standard deviation from the average of the four trials ran on your solution
using the equation below and all of your trials. Show all of your work in your lab notebook.
Standard Deviation =
å(x - average)
2
number of samples
4. Open a new tab in excel and construct a new graph with the same four dairy solution data points, but
add the string cheese portion. Open one more new tab and create a graph including the density of the
four dairy solutions, the string cheese, and the marble. Paste all three graphs below, and make sure to
wrap text to the “Square” option.
Conclusion Questions:
1. How do the densities of the dairy solutions compare to the dairy solutions’ namesakes? Can you
identify a trend?
2. How do the densities of the liquid solutions compare to the densities of the string cheese and the
marble. What does that tell you about these substances at the particulate level?
3. Were your individual results “precise” (ie. did you have a very low standard deviation)?
4. What could have been some possible sources of error in this lab for your group?
5. Can you figure out what differentiates each of the dairy products from each other?
6. Is it wise to bet Astor $5 that Heavy Cream is lighter than Light Cream?
7. Use the particulate cards to pick particulate level examples for each of the substances. Why did you
pick the ones you did? What does it say about the atomic structure of these substances?
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LABS