Add 5 mL of dilute hydrochloric acid. Cover the test tube to prevent the gas from escaping. Light a match and bring it close to the mouth of the test tube. Hydrogen gas is produced in the reaction between the zinc and hydrochloric acid. This gas is highly flammable and gives off a characteristic small explosion, when ignited in a test tube.
Teacher holds an open bottle of ammonia and lets the students take a weft.
Explain that the pungent odor is ammonia gas escaping from the water in which it is dissolved. Students' responses during the activities and follow-up discussions.