Question

A student added 5 grams of calcium chloride, a white solid substance, to 15 grams of water at 22°C. Several observations were made, and the student inferred that a chemical reaction occurred. Which observation best supports the student's inference that a chemical reaction occurred?

a) The calcium chloride dissolved in the solution.
b) The mass of the solution totals 20 grams.
c) The temperature of the solution is 35°C.
d) The solution became lighter in color.

Answer 1

The observation that best supports the student's inference that a chemical reaction occurred is the solution becoming lighter in color.

Step-by-step explanation:

The observation that best supports the student's inference that a chemical reaction occurred is d) The solution became lighter in color.

When a chemical reaction occurs, it often leads to a change in color or the formation of a new substance.

In this case, the white solid calcium chloride reacted with water to form a solution, resulting in a lighter color.

The other observations, such as the calcium chloride dissolving, the mass of the solution totaling 20 grams, and the temperature of the solution being 35°C, can be attributed to physical changes rather than a chemical reaction.