Models of Matter
Grades 4-5 | 20 sessions
Students learn about the particulate nature of matter (atoms and molecules), phase change, and using properties to separate mixtures. They also learn to make inferences and use text features as they read, and to write scientific explanations. They learn and use scientific vocabulary, such as molecule, energy, evidence, and evaluate.» Download Unit Description
Students engage in hands-on activities, such as separating an ink mixture using paper chromatography. Students also investigate phase change by testing faster and slower methods of melting ice.
Students are provided with many opportunities for small group discussions to help them make sense of science ideas. For example, students discuss observations and use evidence to make explanations about ink molecules.
Students read four science books, including Science You Can't See, about how several real scientists make inferences as they investigate things—such as atoms, the ocean floor, and extinct dinosaurs—that can't be directly observed. Students use comprehension strategies such as making inferences, and learn how to navigate informational text.
Students write scientific explanations, including an explanation of what happens to water molecules when energy is added. Throughout the unit, students write to record observations and reflect on their learning.
Nature and Practices of Science
The Models of Matter unit introduces students to the concept of the particulate nature of matter- the idea that all things are made of atoms and molecules. Students apply this idea in the context of chromatography- the separation of a mixture, and explorations of phase change.
Particulate nature of matter: All matter is made of atoms, tiny particles too small to be seen without powerful tools. A molecules is a group of atoms bonded together. Molecules and atoms are always in motion. The molecules of a substance are all the same, and have particular characteristics such as size, weight, and amount of stickiness to other kinds of molecules. Because of this, each substance has characteristic properties such as color, boiling point, melting point, and attraction to other substances. Most matter is made of mixtures of different kinds of substances.
Using properties to separate mixtures: The properties of substances can be used to separate mixtures. For example, a mixture can be separated based on the temperatures at which the different substances in the mixture change phase, or based on the size, weight or other properties of the molecules of the different substances in the mixture. Chromatography is an important technique that scientists use to separate a mixture based on the characteristics of the molecules of substances in the mixture.
Phase change: Matter can exist in different phases, including solid, liquid, and gas. Adding or removing energy can cause matter to change phase. Different phases of a substance have different amounts of molecular motion and different spacing of molecules. In a solid, the atoms or molecules are close together and fairly rigid, though vibrating. In a liquid, they move more and can slide past one another. In a gas, they are much more spread apart and move much faster. Different substances have different temperatures at which they change phase.