This can be achieved with a standard handout, or written part of report, or in quizzes - both oral and written. You may discuss the safety labeling on the zinc metal and acid containers as this is being done. You may elect to pour the acid over the metal or have an assistant pour the acid, while you stretch the balloon opening over the mouth of the flask. Be sure that someone holds the flask securely and that they are aware that it will become warm to the touch. If there is not enough gas in the balloon, simply remove it, again holding it very securely, and add more reactants.
Variations are endless.
You may come up with your own buzz word or phrase for safety awareness, or you may have the class work together with you in a brainstorming process to choose yours. Cooperative learning groups may be used to determine appropriate words or phrases that accompany your buzz word. Creative skits may be generated by cooperative learning groups, or of course you could make your own instead of using the one attached. Current Physical Science or Chemistry texts. Following skit, or one of your or your students composition.