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Dissolving Race; NSRC Science and Technology for Children
 Lesson
at a Glance:
Curriculum: NSRC Science and Technology for Children, Changes, Carolina
Biological Supply Company
Grade: Second
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.
Rosinda: “After
summarizing the comparisons in a Venn diagram, we then proceeded
to
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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