The purpose of this activity is to allow students to think critically to answer a seemingly simple question. In this case, it’s answer an old idiom that says a new broom sweeps cleaner than an old one. You can either examine that question literally (which is what this experiment covers), or the students can look at this question figuratively (do newer products work better/are more reliable than old products?). The students will need to use the scientific method to determine a way to answer that question. They will also need to design a test to empirically show that a newer broom does the job better than an older one.
This experiment is a great way to integrate idioms and math with science. This lesson includes the entire packet to conduct the experiment, but feel free to make adjustments as you see fit!