Classify each of the observed changes according to whether or not they are likely to represent evidence that a chemical reaction is occurring when performing an experiment.

Question

1.) bubbles (gas formation)

2.) explosion or fire

3.) changes in color

4.) a solution color becoming less intense due to dilution

5.) precipitation

6.) changes in temperature

7.) a solid liquifying

8.) solution colors mixing

Answer 1

1.) bubbles (gas formation) = Chemical reaction

2.) explosion or fire = Chemical reaction

3.) changes in color = Chemical reaction and sometimes formation of precipitate at the same time

4.) a solution color becoming less intense due to dilution = does not involve chemical reaction and still have the same substance that is present except in a lower concentration.

5.) precipitation = usually goes with a chemical reaction

6.) changes in temperature = if no external heat source is being used, then you are likely in presence of a chemical reaction either exothermic or endothermic reaction.

7.) a solid liquifying = could be a physical change not involving a chemical reaction

8.) solution colors mixing = could be a physical change not involving a chemical reaction

For some of the change, additional information might be needed in order to draw a clear conclusion.

I hope it helps!