Question

State an observation in an activity which may suggest that a chemical reaction has taken place.Give examples in support of your answer.

Answer 1

In a tube take small amount of solid sodium carbonate (Na₂CO₃). To this add a few drops of hydrochloric acid.

A colourless and odourless gas will evolve which shows that a chemical reaction has taken place. The gas will turn lime water milky when passed through it.