Lesson 2: Percent Compositions

For the teacher:

Students are arranged in sets of four that can be broken up into pairs

• Phenomena: Have students watch "Investigation shows Subway's 'chicken' contains only about 50 percent chicken DNA." Students will record any observations or thoughts they have about what the saw.
• Generated Questions: Have students complete Inquiry Reflection (attached) parts 1 and 2. Part 1 is what they saw in the video. Part 2 are questions that the students generate about the phenomena. This is all done in groups electronically on a Google Doc.
• Investigation: 2 part investigation:
  1. Students will work on the ChemQuest* investigation where they read through information, answer critical thinking questions, and then compare their work with a partner. Students will confirm their answers with the teacher in class discussion and put answers on the board.

*ChemQuest is copyrighted material, but can be found and purchased here:

2. Students will choose between two exercises where they will determine mass percents. Click on the links below

A. Percent composition of Oreos

B. Percent composition of bubble gum

• Task: Teacher tells students to resume Inquiry Reflection to complete the “Task” section. “Discuss with your partners, and write an explanation of how you calculate what something is made of.” Students submitted work electronically, but can be submitted on paper.

Student Sample: (Completed by 11th grade students)

Inquiry Reflection--Percent Composition

Make a copy of this document and share with your partners and instructor.

Names: Mckenzie, Kacey, Blake

• Phenomena: What did you see in the video? What did you notice? What was interesting? Why?
  • That things aren't always what they appear.- Blake
  • Because the chicken isn't actually chicken.- Blake
  • Because I'm paying for chicken but Im not actually getting it.- Blake
  • Restaurants usually have false statements about their meals- Mckenzie
  • I noticed that the chicken isn't even half the chicken at subway because they add all these different things in the chicken that it's only about on average 40% chicken. - Mckenzie
  • Uggghhh. Gross-Blake
  • The interesting thing is that it appears that they are allowed to lie about how much chicken people are actually getting. -Mckenzie
  • That the chicken wasn't all chicken.-Kacey
  • That the places I thought were good and reliable, weren't really telling the truth- Kacey
  • It was interesting because i didn't think that subway would have lesser of a chicken factor than McDonalds.-Kacey
• Questions: What questions do you have about this topic?
  • Why would they say its 100% chicken if it's really not? Why would they lie about it?- Mckenzie
  • If I order chicken why can't it be 100% chicken?- Blake
  • Do they have other products that are not 100% what they say they are?-Kacey
  • How do scientists test the percentages of food?-Kacey
  • What else can be measured in % ? -Mckenzie
• Investigation:
  • Work on the ChemQuest individually. Here is a student sample.
  • Work on one of the two inquiry investigations
    • A. Choice: Percent of Oreo Composition--Student work sample is here.
• Task: Using at least 1 example per person in each group, Identify and complete a written explanation of how percent composition is applicable in real life. Be sure to be detailed in your explanation of how the percentages work.

STUDENT RESPONSES:

Percent composition- this is applicable to real life because you can use this to check the amount of beef there is in a product. You measure the different products that go in the beef product and turn that into a percent.--Blake

Percent composition is applicable in real life whenever you are trying to find out the percentages of food. For example, when you are at the grocery store and you want to figure out how much food you are getting for what you're paying for you look at how much it cost and then you find out how much it comes with. So you can use this to figure out if you're getting your money's worth. -Kacey

When you are buying candy you divide the number of boxes of candy by the total price to see how much the candy is. Or, when you’re buying medicine you can use the percent composition to see how much of each ingredient is in the medicine. --Mckenzie

ANNOTATION:

This lesson was aligned to NGSS HS-PS1-7.

This lesson occurred over a 2 day period.

Day 1: The students were hooked from the beginning with the video. Many students like Subway sandwiches and the video grossed some of the out! Knowing that the "chicken meat" that they were eating was less than 50% chicken DNA was eye opening. The video did a good job showing the data with percents and the students caught onto the percent theme. After the video I had the students stop and open up an Inquiry Reflection on a shared google document (this could be paper based). The students in their groups had to respond to the phenomenon and question sections first. I gave the students 6 mins to respond to these sections electronically. Students put their names or initials beside their responses or questions since they were working on a shared document. This kept them accountable. Once they responded each group worked on a ChemQuest investigation for 30 minutes. This handout has the students read and work through information and forces them to think critically about the content. It is not just a typical worksheet. The answers aren't simple. Students had to take provided examples and apply them to their work. The questions are more explanation based rather than recall. The students could work together on this activity and I walked around to ensure that they were focused, on task and addressed any misconceptions. When asked a question I was sure to just guide the students and not directly answer them. I wanted them to figure it out. The PAYOFF is so much greater when they figure it out. Finally, when students finished, we had a 20 minute discussion where we worked through some problems on the board to ensure proficiency with the content. This took longer because students kept asking for more examples to be worked through. If students were not finished with the ChemQuest, it was to be completed for homework because they were going to need that information for part two of the investigation.

Day 2: I started the lesson by having each group quickly discuss how they determine the percent of something and come up with an example. I selected a student from each group to share their example. Then I gave the students instructions to choose from the Oreo or Bubble gum investigation. Students worked on this investigation in pairs but had to submit their own work. I modified the instructions where students had to write their own procedure. I did this because I wanted the students to realize on their own the proper items they needed to mass to ensure proper percentage calculations could be performed. Although this investigation was not using "hard core chemistry materials" the process was the same as if it were. As students finished the investigation, I had them return to their original Inquiry Reflection and respond to the task section. Students had to discuss the prompt with their peers and then record their individual answers on the document.