Skip to main content Skip to main content

Essential Science for Teachers: Physical Science

Physical Changes and Conservation of Matter Featured Classroom: Rosinda Almeida, Cambridge, MA

Rosinda Almeida, Cambridge, MA

“When students are into their experiments with hands and minds, they will always come up with questions that challenge the extent of my understanding. That’s what teaching is all about.”


School at a Glance:
Benjamin L. Banneker Charter School
Cambridge, MA

  • Grades: K-8
  • Enrollment: 345
  • Students per teacher: 15
  • Ethnicity:
    2% White
    6% Hispanic
    91% African American
  • Percentage of students receiving free or reduced-price lunch: 69% versus a state average of 30%

The Benjamin L. Banneker Charter School is in the third year of implementation of a laboratory-based experimental science curriculum called Hands-on Science. The Science and Technology for Children (STC) series of science units forms the instructional basis for the curriculum in grades 1-6, where each science teacher is free to implement the curriculum as developed and/or to supplement and expand with additional hands-on science content as needed.

Rosinda Almeida teaches second grade at the Banneker. This is Rosinda’s fifth year of teaching and second year at Banneker.

Rosinda: “I like using laboratory science instruction because it explores a science concept over a number of weeks, and is a more effective method for bringing about an understanding than using one-time experiments or simply talking, reading, and writing about science concepts.

“ My thoughts about what’s important about teaching science is that it gives students the opportunity to think critically. I try to set an example of how we all learn by having a discussion at the beginning of every lesson. In this way I seek their prior understanding by asking them questions. I find that one useful strategy of science teaching is using analogies and models that are based on students’ prior experiences.”

Lesson and Curriculum

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.”

Series Directory

Essential Science for Teachers: Physical Science


Produced by Harvard-Smithsonian Center for Astrophysics. 2004.
  • Closed Captioning
  • ISBN: 1-57680-749-5