In school, Jarrett learned that salt lowers the freezing point of water. He wants to test this in a home experiment. He adds an equal amount of salt and room-temperature water into three identical containers. What is a control of his experiment?

Answer 1

There is no control in this experiment.........

One or two of the containers should NOT have contained salt. Given a salt solution and a solution of pure solvent, a differential freezing point may have been observed.

Of course, to make the solutions in the beakers freeze, he would need an ice-salt or ice-ethanol bath, in which to immerse his containers.

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Answer 2

Jose Ayala

The control of Jarrett's experiment would be a container with only room-temperature water and no added salt.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.