Burning a Marshmallow – Percent Composition of a Marshmallow

WARNING – NEVER eat or drink anything in the lab.

Objective: Discover percent composition of carbon in a marshmallow for S’mores Candy Company and compare it to expected results.

Materials:

·  Marshmallows

·  Wooden bamboo skewer or metal tongs

·  Bunsen burner or candle

Procedure:

1)  Weigh the marshmallow. (Take the mass of the marshmallow in grams BEFORE you burn it!)

2)  Carefully insert skewer through marshmallow or hold with tongs.

3)  Hold over flame until it is completely burned – there should be no “white stuff” remaining at all.

4)  Take the weight of the burnt marshmallow. (The mass of the marshmallow after burning, NOT a burning marshmallow.)

5)  Calculate percent mass of carbon in the marshmallow. (You need to have calculated molar mass of a marshmallow (C12H22O11) and percent composition of each of the elements present.)

6)  Calculate percent yield. (How accurate was your laboratory experiment? Was your percent error within + 0.03 (+3%)? Should S’mores Candy Company continue to use this process to perform their laboratory analysis or should they find another method to produce better results? What process or what type of process would you recommend?)

Explanation:

Marshmallows are composed primarily of sucrose, or cane sugar. The formula for sucrose is C12H22O11. The hydrogen and oxygen ratio in sugar is the same as that for water or H2O – a 2:1 ratio. As the marshmallow burns, its hydrogen and oxygen is released as water vapor. The black part of the marshmallow represents unburned carbon in the marshmallow – which is all that remains once the hydrogen and oxygen leave. The release of these gases causes the marshmallow to expand considerably.

The mass of remaining black part of the marshmallow is about 40% of the original mass of the marshmallow. The rest was released as water vapor.

Anytime food is burned and it turns black, the carbon is being separated from the rest of the food. If something is burned long enough, nearly all that remains is carbon – definitely not very tasty.

Lab Results

Describe what you observed during the process of burning the marshmallow.

Data Table

Trial 1 / Trial 2 / Trial 3
Original mass (g)
Burnt mass (g)
Grams “lost” (Subtract original by burnt mass)

What is the percent mass of both water and carbon in the mass marshmallow based on your results?

Trial 1 –

Trial 2 –

Trial 3 –

What is the expected value for carbon of the marshmallow? (Show your math!)

Trial 1 –

Trial 2 –

Trial 3 –

Based on your laboratory results would you recommend that the S’mores Candy Company use this method for determining percent mass in their factory? Why or why not? Keep in mind: (How accurate was your laboratory experiment? Was your percent error within + 0.03 (+3%)? Should S’mores Candy Company continue to use this process to perform their laboratory analysis or should they find another method to produce better results? What process or what type of process would you recommend?) SHOW YOUR WORK/Math!

Based on Combustion Experiment # 6: Burning a Marshmallow by Rohrig, B. (1997, 2002). 150 captivating chemistry experiments using household substances. Fizz Bang Science.