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
Light Cream
1%, 2%, Skim, or Whole Milk
100 mL Graduated Cylinder
Digital Mass Scales
Dixie Cups
Pipet
String Cheese
Marbles
Lab:
1. Each group will be assigned a random milk (Whole Milk, 2%, 1%, or Skim Milk) and either Heavy
Cream or Half-and-Half along with a piece of String Cheese. Each group will measure the mass and
volume of each mixture, before calculating density and comparing these values to the density of a
solid marble.
2. You will begin with assorted Milk product you were assigned. First, you will measure out 10 mL of
milk with a graduated cylinder. Then place a Dixie cup on the digital mass scale and press the
tare/zero button. Once the weight value shows 0.00 g, pour the milk into the cup and record the mass
value given. Do this again with 20 mL and 30 mL. Record all values.
3. Next, grab your other liquid dairy product and choose a volume between 10-20 mL that is easy for
you to measure. 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.
4. Using the digital scale and Dixie cups, place the Dixie cup on the scale and press the tare/zero
button. Once the weight value shows 0.00 g, pour the solution into the tared Dixie cup and record the
new mass value.
5. Use the mass and volume of each to calculate the density of the respective dairy solutions.
6. Next, use the Dixie cups and digital scale to weigh out the given portion of string cheese. Record the
mass.
7. 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.
8. Repeat the trail for the marble. Using the mass and volume collected, calculate the density of both.
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LABS
Results/Discussion:
Data Table:
Table 1.Measurement values for different dairy products.
Substance
Milk
Milk
Milk
(10 mL)
(20 mL)
(30 mL)
Half and
Half
Heavy
Cream
String
Cheese
Mass (g)
Volume (mL)
10
20
30
Density
(g/mL)
Analysis: To be answered from data in Table 1.
1. Groups will enter their density data into this google spreadsheet. Then, each group will individually
take the average density of each substance by adding the contents of each row and dividing by the
number of entries.
2. Use excel to create a scatter plot graph comparing the dairy solutions (Whole Milk, Skim Milk,
Reduced Fat Milk, Half and Half, and Heavy Cream,) to their density with five-six 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 trials run 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 five-six dairy solution data points,
but add the string cheese portion. Open another new tab and create a graph including the density of
the five-six dairy solutions, the string cheese, and the marble. Open one last tab and graph the mass
vs. the volume for all three milk trials. Add a trendline and show the equation. Copy and paste all
five graphs below in the order listed, and make sure to wrap text to the “Square” option. Use the
Chemistry and Microsoft Excel document to help you with this process.
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. Look at the graph of mass vs. volume for Whole Milk and Heavy Cream. Which trendline has a
steeper slope? Why? What does the slope of the line represent? How can you calculate it?
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. What could have been some possible sources of error in this lab for your group?
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