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Percent Composition Mark as Favorite (16 Favorites)

LAB in Percent Composition, Measurements. Last updated March 19, 2020.

Summary

In this lab, students will calculate the percent composition of sugar in gum and the percent composition of water in popcorn kernels.

High School

NGSS Alignment

This lab will help prepare your students to meet the following scientific and engineering practices:

• Scientific and Engineering Practices:
• Using Mathematics and Computational Thinking

Objectives

By the end of this lesson, students should be able to:

• Calculate the percent composition of a substance in a sample.

Chemistry Topics

This lesson supports students’ understanding of:

• Percent composition

Time

Teacher Preparation: 10 minutes

Lesson: 1 hour

Materials

For each group:

• Bubble gum
• Balance
• Timer
• 75 popcorn kernels
• Heavy duty aluminum foil
• 250-mL beaker
• Bunsen burner
• Tongs/forceps
• Goggles

Safety

• Goggles should be worn throughout the experiment.
• Food should never be consumed in a lab setting. The group member who chews the gum should do so outside of the lab.
• The gum should never touch the surface of the balance. Only the gum chewer will handle their piece of gum.
• Always be cautious around a Bunsen burner. If you don’t feel comfortable lighting it yourself, ask your teacher for assistance.
• Always be aware of an open flame. Do not reach over it, tie back hair, and secure lose clothing.
• Food should never be consumed in a lab setting. Do not eat the popcorn, it should be discarded once the final data are collected.

Teacher Notes

• Remind student that the food they’re using in this experiment should be treated as chemicals, not as food.
• The chewing of the gum should be done outside of the lab. Have the students chew the gum in the hallway outside the lab, for example.
• The gum can never touch the balance. Cover the surface of the balance with a paper towel and use the gum wrapper as a second layer when finding the mass. The mass of the wrapper cannot be included in the initial mass because it will affect the final calculations when determining the percent composition of sugar in the gum.
• Don’t discard the gum wrapper, it will be used to mass the gum sample. Class data could be collected for this part, so only three or four students are chewing gum outside of the lab for three 5 minute intervals.
• For the foil basket, use a 250-mL beaker as a mold for the aluminum foil bowl. Use another piece to cover the top, sealing it so that popcorn does not fly out. Heavy duty aluminum foil works best, but regular will work as well. Students should be careful not to hold the aluminum foil bowl directly over the flame. They should wave it occasionally and shake it several times during the popping process. Otherwise, the Bunsen burner will cause a hole to form in the bottom of the bowl. They should also use tongs or forceps to hold the bowl over the flame NOT THEIR HANDS!

Lesson

Problem

What is the percent composition of sugar in bubble gum and water in popcorn?

Safety

• Goggle should be worn throughout the investigation.
• Food should never be consumed in a lab setting. The group member who chews the gum should do so outside of the lab.
• The gum should never touch the surface of the balance. Only the gum chewer will handle their piece of gum.
• Always be cautious around a Bunsen burner. If you don’t feel comfortable lighting it yourself, ask your teacher for assistance.
• Food should never be consumed in a lab setting. Do not eat the popcorn, it should be discarded once the final data are collected.

Materials

• Pieces of bubble gum (different flavors)
• Balance
• Timer
• 75 Popcorn kernels
• Heavy duty aluminum foil
• 250-mL beaker
• Bunsen burner
• Tongs/forceps
• Goggles

Procedure

BUBBLE GUM
1. Identify who will be the gum chewer. They will need to chew a piece of gum for 15 minutes.
2. Determine the mass of the unchewed gum. The gum cannot touch the surface of the balance. Note the flavor. Do not discard the wrapper.
3. Chew gum for 5 minutes.
4. Remass the gum, making sure it does not touch the balance.
5. Repeat for two more 5 minute chew cycles, remass after each cycle.

POPCORN
1. Determine the mass of 25 popcorn kernels.
2. Use aluminum foil to make a bowl for the kernels. Use a 250-mL beaker as a mold for the bowl, but do not keep the foil in the beaker.
3. Place the kernels in the bowl. Use another piece of foil to cover the bowl and seal the two pieces of foil by folding them together so the popcorn does not fly out.
4. Pop the kernels carefully over the Bunsen burner, using the tongs or forceps to gently heat the aluminum bowl. Shake regularly to ensure not burning a hole in the aluminum.
5. Once your kernels have all popped, take the final mass of the popcorn.
6. Dispose of the popcorn, do not eat it.
7. Repeat the steps for a second and third set of data.

Results

 Flavor Mass of unchewed gum on wrapper Mass of wrapper alone Mass of unchewed gum Mass of gum on wrapper after 5 min chewing Mass of gum after 5 min chewing Mass of gum on wrapper after 10 min chewing Mass of gum after 10 min chewing Mass of gum on wrapper after 15 min chewing Mass of gum after 15 min chewing Mass lost (unchewed gum - gum after 15 min chewing)
 Sample # Mass (unpopped), g Mass (popped), g Mass lost, g 1 2 3

Calculations

BUBBLE GUM

 % Composition of sugar = Total mass lost x 100 = Original mass of gum

Draw a graph of mass of gum vs time on the graph to the right:

Explain what the graph shows:

POPCORN

 % Composition of water = Mass lost x 100 = Mass (unpopped)

Sample 1:

Sample 2:

Sample 3:

Average % of water in three samples:

Conclusion

1. If you chewed the gum for five more minutes, what do you think would have happened?
2. What else might have caused a change in the mass of the gum?How would that affect your calculations?
3. How does popcorn pop?
4. How might older popcorn kernels differ from the data you collected in this investigation?