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The purpose of the assessment probe, in this chapter, is to elicit children’s ideas about floating and sinking. The probe is designed to find out if children think size is the property that determines whether an object floats or sinks.
In this chapter, the purpose of the assessment probe is to see the ideas of children with the subject: sink or float. The probe is created to find out if students think that size plays a big role when it comes to either sinking or floating. Some popular answers while doing an experiment on both a watermelon and grape to test in water whether or not each fruit will either sink or float is that “The watermelon will float” and “The grape will sink”. I feel like with the subject sink or float, students believe that the bigger the object is, the more it will float and the smaller it is, the more it will sink when really, it’s the opposite. It all has to do with the density of the object and how much greater it is than the water or not. For example, as stated by Page Keeley, “The density of a grape is greater than that of the water; therefore, it sinks.” Overall, what is important is for students to determine that the size alone of an object, doesn’t determine whether or not an object sinks or floats. By doing the experiment: Watermelon and Grape, that will provide them with the experience that big objects that float and small objects that sink, and vice versa. Considering that I’m a pre-service teacher, I really enjoyed reading this book chapter as it gives me ideas while conducting this experiment with kids. This is definitely a good book chapter to recommend to colleagues!
The probe asks students to look at which floats, a grape or a watermelon. Young students are apt to provide an answer based on size, not a mass to volume ratio which is what density is. This probe could be challenging to older students. Keeley does a good job helping guide teachers how to best implement the probe in the classroom.
Susan German (Hallsville, MO)
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