Physical Science: Session 3
Dissolving Race; NSRC Science and Technology for Children
at a Glance:
Curriculum: NSRC Science and Technology for Children, Changes, Carolina Biological Supply Company
Topic: Dissolving Race
Rosinda follows the STC “Changes” lesson plans fairly closely.
Rosinda: “In Lesson 7 (A Dissolving Race: Two Forms of Sugar), we simply compared two forms of the same substance, a sugar cube and granulated sugar. Students observed that both forms are sugar and differ only in the overall size of their pieces. After dropping a sugar cube and an equal volume of granulated sugar into two separate cups of water, the students observed that sugar dissolved faster when it is in smaller pieces and when it is stirred.
“When we moved on to Lesson 8 (A Dissolving Race: Warm and Cold Water), the students quickly picked up from the previous lesson and were enthusiastic about doing the experiment mixing granulated sugar with cold and warm water, and discussing the relationship between water temperature and the speed at which sugar dissolves. I was particularly pleased when one of my students, mindful of ‘controlling’ the time variable, admonished her lab partner to ‘put the sugar in the hot and cold water at the same time!’”
In the following lesson (Changing Salt Water to Crystals), Rosinda’s students returned to their earlier observations where they had set up salt and water solutions in petri dishes. Students observed and discussed the process of evaporation, and compared the appearance of salt before and after evaporation. When the students added water to their salt crystals in the petri dishes, they discovered that the crystals could dissolve again to form a salt-and-water solution.
summarizing the comparisons in a Venn diagram, we then proceeded
predict what would happen if water were again added to the petri dishes. I found that these investigations helped my students to understand that a substance can sometimes undergo a change in appearance, yet remain the same substance.”
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