The squeaky pop test is an experiment to demonstrate the fact that hydrogen gas is created when most metals come in contact with an acid. The experiment begins by placing a metal strip such as magnesium into a test tube of acid.
As the reaction between the metal and acid occur, the hydrogen gas can be seen bubbling up from the acid. First, a test tube is placed upright, then metal and acid are added to the tube. Next, a second test tube is placed in an upside down position on top of on the test tube containing the acid and the metal. As hydrogen gas forms, it will be contained in the top test tube. After a short time, the top test tube is quickly removed and covered by a finger to prevent the hydrogen gas from escaping. A match or lighter is used to create a flame. Then, the flame is placed at the entrance of the test tube filled with hydrogen gas. Finally, finger is removed from the hydrogen gas test tube and as the hydrogen flows from the tube it meets the flame and burns, a squeaky pop noise is created.
In summary, hydrogen is a colorless odorless gas. The squeaky pop noise is created when it burns is used to identify and verify its existence during this experiment.