Being rigid in doing experiments is a teacher's quality, but you don't have to pay too much attention to details when explaining to junior high school students. If you talk too much, students will become ignorant.

In the first experiment, students were asked to observe the experimental phenomenon, and the explanation was that paper tubes spread acoustic energy centrally, similar to a doctor's stethoscope. no need to say any more The main reason for not taking this exam is to improve students' interest. If students are interested in experiments, they will succeed.

Just show the students the second experiment. Don't explain the details of the experiment and how to operate it orally.

What students have to do is to observe that compared with when there is no sound, the flame of the candle is moving, and the flame will not move for no reason. What does this mean? (Students may answer: There is energy, provided by sound). How does this energy spread? (air)

Let the students answer by themselves. Don't explain if you get it right.

In fact, students don't care about experiments. If the teacher fails in the experiment, the students are happiest. Don't do the experiment if you can't guarantee the success rate. Don't do time-consuming and laborious experiments. Your two experiments are time-consuming and laborious, and they are not the focus of the exam. Play them on video.