There are certain foods that you think of as being sweet and contain sugar, such as candy bars, sodas, and cookies.

Source: Green Onions, Dole.com

What about green onions? Do you think they contain sugar?

Benedict’s solution is an indicator that is used to test for the presence of sugar. Complete the online lab below to determine if green onions contain sugar.

Write your answers on a piece of paper to the following questions about the lab activity.

1. Why was a sample of plain water tested?

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   A test tube with plain water was tested to ensure that the Benedict’s solution would not turn a different color when heated.

2. Why was a solution tested that was known to contain sugar?

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   A solution with a known sugar substance was tested to indicate how the color of the solution should change when sugar is present.

3. How is the presence of sugar in the onion stems determined?

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   The onion stem solution turned a reddish-orange color indicating the presence of sugar.

4. Identify the control group, independent variable, and dependent variable in this experiment.

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   Control group: test tube 1
   Independent variable: substance added to the test tubes
   Dependent variable: color change

5. What are the constants in this experiment?

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   Constants –
   • All test tubes were heated at the same temperature and the same amount of time using the heat source
   • Same amount of water was added to each test tube
   • Same amount of Benedict’s solution was added to each test tube
   

Sugar was present in the green onion stems. How did the sugar get there? The answer is photosynthesis.