Final answer:
Before a reaction occurs, an unknown metal solution might show qualities such as being colorless and odorless or having a distinct color. Bubbles, effervescence, or a strong odor would suggest a reaction is taking place. Observations involving color changes or precipitate formation are indicators of a chemical reaction.
Step-by-step explanation:
Before any reactions occur in a unknown metal solution, a student might observe several qualities. The solution could have a distinct color or exhibit turbidity if it contains suspended particles. Another possibility is that the solution may be colorless and odorless, which is common for many metal salts dissolved in water. However, it would not yet produce bubbles or effervescence, as this would indicate a reaction taking place, nor should it have a strong, unpleasant odor unless it was reacting or contained a volatile component.
For example, a scenario could involve mixing two solutions where a reaction is observed: A green solution and a colorless solution are mixed to yield a solution with a pale green color. In another case, two colorless solutions could be mixed, resulting in a mixture that has a yellow precipitate. These color changes and the formation of a solid precipitate are visual cues that a chemical reaction has occurred.
In the context of an experiment where the test tube contains a clear, colorless salt solution, and upon adding silver nitrate, a pale yellow precipitate forms, this indicates the salt reacting with the silver ions to form a new substance. When chlorine water and carbon tetrachloride are added resulting in a purple solution, it suggests that the original solution contained a halide ion, which is able to undergo further reactions to form colored complexes.