Navigating this Pathway
[stextbox id = “info”] In this pathway, students try to explain why weight does not change during phase change. (NOTE: The Next Generation Science Standards (NGSS) do not distinguish between “weight” and “mass” in fifth grade. We use “weight” because the term is more familiar to students.) We recommend having students write the driving question, “What happens to the weight of an ice cube when it melts?” in their science notebook and/or displaying this question prominently in the classroom throughout the pathway. Using their imaginary super strong glasses, students first draw what they would see happening to an ice cube left in a lunch box all day long. Their drawings will give the teacher a sense of what ideas students have about particles and phase change. Students then predict what will happen to the weight of an ice cube when it melts and compare their prediction to what actually happens. They draw a model to attempt to explain why the weight does not change. Their drawings should reveal whether they understand that matter is made of particles, which are neither created nor destroyed during phase change. Next, students watch a computer simulation that shows what happens at the particle level during phase change. Finally, using their super strong glasses, students draw once more what they would see in the ice cube and liquid water. These drawings will help the teacher see how students’ thinking has changed over the pathway.[/stextbox]
Connections to Other Pathways
[stextbox id = “info”] This pathway does not depend on doing any other pathways first. Although doing this pathway before the others is not at all essential, it does introduce students to the idea of particles, which they can use to explain phenomena in the other pathways.[/stextbox]
Teacher Content Background
[stextbox id = “info”] All matter is made of particles that are too small to see, that are in constant random motion, and that have empty space between them. “Empty space” is literally empty; that is, nothing at all is between the particles that make up matter, which explains why matter (especially gases, but also solids and liquids to a lesser extent) can be compressed. All of the particles present in one state (solid ice) are present in the other (liquid water). No particles are destroyed and none are added. In addition, the size and shape of the particles does not change. Therefore matter, and mass (or weight), is conserved (stays the same) during phase change, contrary to what many students think.[/stextbox]
Student Thinking
[stextbox id = “info”] Students are all familiar with melting ice, but this driving question will confront them with the commonly held idea that weight changes during phase change (Aydeniz & Kotowski, 2012; Durmuş & Bayraktar, 2010; Lee, Eichinger, Anderson, Berkheimer, & Blakeslee, 1993; Stavy, 1990a, 1990b ). Students may also think that the size or shape of particles change during phase change (Aydeniz & Kotowski, 2012; Özmen, 2011; Özmen & Kenan, 2007; Tsai, 1999).[/stextbox]
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Student Experiences
[stextbox id = “info”]- Student Experience 1: Imagining Phase Change
Students imagine what they would see with “super strong glasses” as an ice cube changes phases. - Student Experience 2: What Happens to the Weight of Ice When it Melts
Students predict whether the weight of an ice cube will change or stay the same when it melts, and then observe to see what happens. - Student Experience 3: Imagining Phase Change, Part 2
Students again make drawings of phase change using their super strong glasses. - Student Experience 4: States of Matter Simulation
Students observe phase change using a computer simulation. - Student Experience 5: Imagining Phase Change, Part 3
Students revisit their super strong glasses drawings and revise using their new understanding.