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Bromothymol blue (BTB) is a chemical that turns yellow in the presence of carbon dioxide. In the presence of oxygen, BTB stays blue. In his science class, Sanjay used BTB to test for the presence of those two gases in three situations.

*Sanjay's Procedure*

Sanjay labeled three small jars A, B, and C. In Jar A, he put two aquatic snails. In Jar B, he put two sprigs of Elodea, an aquatic plant. In Jar C, he put two snails and two sprigs of Elodea. Sanjay added BTB solution to the jars so the snails and Elodea sprigs were covered. Then he put the lids on tightly and placed the jars in a sunny place.

*Sanjays Results*

Sanjay examined the jars every day for three days. These are the observations he recorded:

Jar A: The BTB turned yellow.
Jar B: The BTB solution stayed blue.
Jar C: The BTB solution stayed blue.


1. Why did the BTB solution in Jar A turn Yellow?

2. Why did the BTB solution in Jar B stay blue?

3. Why did the BTB solution in Jar C stay blue?

4. Which jar showed what happens during the carbon and oxygen cycles in nature? Describe the process that occurred in that jar.

  • biology -

    If you would like to put forward some answers we will be pleased to comment on them.

  • biology -

    question 1 answer:because its exposed to caebon dioxide.

  • biology -

    question 2 : the elodea gives off oxygen which lets the BTB stay blue

  • biology -

    Because it can

  • biology -

    I don't really know

  • biology -

    1. There's carbon dioxide which makes the BTB yellow
    2. There's no carbon dioxide, just oxygen
    3. I really don't know

  • biologyhdjdbeb -


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