Essential Science for Teachers: Physical Science
Chemical Changes and Conservation of Matter Featured Classroom: Rebecca Cituk, Portsmouth, RI
Rebecca Cituk, Portsmouth, RI
“My interest in science started with my love of the outdoors and when I began wondering why things work the way they do. I feel that also from my students. Every time we do science experiments, they keep asking why, you know, and they want to know why is the sky blue, for example. I feel like teaching is a learning experience for everyone involved, including the teacher. I want my students to realize that I’m still learning, too, that it doesn’t stop here. And for them, that’s how it will be, and that this is just a stepping stone to the next adventure that is coming for them.”
School at a Glance:
Portsmouth Middle School
- Grades: 5-8
- Enrollment: 924
- Students per Teacher: 14.4
2% African American
- Percentage of students receiving free or reduced-price lunch: 6% versus a state average of 38%
Rebecca has been teaching for seven years — the last four at the Portsmouth Middle School. She is currently enrolled in a master’s in science education program at the University of Rhode Island, and also participates in a summer program in the engineering department at Brown University called “Research Experience for Teachers,” where she has developed modules that integrate math and science.
Portsmouth Middle School is divided into “learning centers,” each with about 70 students. Each learning center is in a square that’s divided by walls that can open and close. In Rebecca’s center, there are three classrooms and one open classroom. The students rotate from one class to the other and see different teachers throughout the day. According to Rebecca, “The whole concept behind it is that it gives the teachers an opportunity to work as a team… We can open up the walls and do something as a whole group, or we can close them up if we need to. Most of all, it allows us to give the students an environment where they feel safe to ask us questions, and where they feel comfortable.”
Lesson and Curriculum
Describe a New Substance; EDC Insights
Lesson at a Glance:
Curriculum: EDC Insights, The Mysterious Powder, Kendall-Hunt Publishers
Grade: Upper elementary
Topic: Learning Experience 10: Using Science Skills to Describe a New Substance
Prior to this lesson, Rebecca’s class had been working for four weeks, investigating the different mystery powders, and trying to identify them by observing their properties during various chemical reactions.
In Rebecca’s adaptation of this lesson, the class took two substances that they were familiar with, baking soda and vinegar, and mixed them together. “They knew that there was going to be a chemical reaction,” says Rebecca, “but we took it a step further and put them into a closed container and weighed them before and after they were mixed, to see if the matter would be conserved.”
The first time the students did the experiment, they put a balloon over the top of the bottle in which the reaction occurred, so they could watch the newly created gas fill the balloon. When the class weighed their bottles afterwards, however, several students found that their bottles weighed less than they had before the reaction took place. Thinking that either the balloons had small holes in them or that the seals were leaky, Rebecca rethought the experiment and had the students replace the balloons with the bottle caps.
She recounts, “This time the students found that the substances weighed the same before and after they were combined, even though some of the matter disappeared from view. And I think it’s important that students realized that, sometimes in science when you do an experiment, it doesn’t always go the way you expect.”
After this lesson, Rebecca did several follow-up lessons where the students investigated conservation of matter through other chemical reactions. “It’s kind of a hard concept,” she said, “because if you watch a piece of wood burn, it seems to be gone. So, the idea is to get students to understand that it’s not gone; it’s just changed its form.”
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.