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
- Grades: K-8
- Enrollment: 345
- Students per teacher: 15
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
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.”
Session 1 What Is Matter?: Properties and Classification of Matter
What is matter? This question at first seems deceptively simple — matter is all around us. Yet how do we define it? What does a block of cheese have in common with the Moon? What are the characteristics of matter that set it apart from something that is definitely not matter? Matter is one of the big ideas in science. Most areas in physical science can be discussed and explained in terms of matter or energy, and matter is a subject that naturally bridges to the other sciences (chemistry, life, earth science, etc.). In this session, we’ll build a working definition of matter, learn to distinguish between its “accidental” and “essential” properties, and explore it through classification, an activity with a rich history in science.
Session 2 The Particle Nature of Matter: Solids, Liquids, and Gases
What simple idea links together all of chemistry and physics? How can a close study of the macroscopic differences among solids, liquids, and gases support a microscopic model of tiny, discrete, and constantly moving particles? In this session, participants learn how the "particle model" can be turned into a powerful tool for generating predictions about the behavior of matter under a wide range of conditions.
Session 3 Physical Changes and Conservation of Matter
What happens when sugar is dissolved in a glass of water or when a pot of water on the stove boils away? Do things ever really "disappear?" In everyday life, observations that things "disappear" or "appear" seem to contradict one of the fundamental laws of nature: matter can be neither created nor destroyed. In this session, participants learn how the principles of the particle model are consistent with conservation of matter.
Session 4 Chemical Changes and Conservation of Matter
How can the particle model account for what happens when two clear liquids are mixed together and they produce a milky-white solid? What happens when iron rusts? Where do the elements come from? In this session, participants extend the particle model by looking inside the particles, learn about some early chemical pioneers, and in the process discover how the law of conservation of matter applies even at the scale of atoms and molecules.
Session 5 Density and Pressure
What makes a block of wood rise to the surface of a bucket of water? Why do your ears pop when you swim deep underwater? In this session, participants examine density, an essential property of matter. They also look at how particles of matter are in constant motion, which leads to a deeper understanding of fluid pressure. Lastly, the concepts of pressure and density are investigated to explain the macroscopic phenomenon of rising and sinking.
Session 6 Rising and Sinking
Why does a hot air balloon rise into the sky? Why does ice rise in water, when a lump of solid wax will sink in a jar full of molten wax? In this session, participants generalize the model that has been developed about what rises and what sinks, using the idea of balance of forces.
Session 7 Heat and Temperature
What makes the liquid in a thermometer rise or fall in response to temperature? Which contains more heat — a boiling teakettle on the stove or a swimming pool of lukewarm water? In this session, participants focus on the difference between heat and temperature, and examine how both are defined in terms of particles. The particle model is then used to explain a number of everyday phenomena, from why things expand when they are heated to the role that temperature plays in changes of state.
Sessions 8 Extending the Particle Model of Matter
In this session, participants extend their understanding of the particle model to explain additional macroscopic phenomena, including the electrical properties of matter. Participants review the progression of ideas covered in the course and anticipate future developments in the understanding of matter.