The unit begins an investigation of substance interactions. Students explore various processes used to separate substances from mixtures. The lessons continue to showcase the most important substance on Earth—water. Students learn about the importance of freshwater and the abundance of salt water. The study of water continues as students learn about the importance of water for life. Then in an exploration of solubility, students discover some substances that dissolve in water. Students continue investigating the characteristics of substances beyond water as the concept of viscosity is introduced. After working with a colloid, students observe its characteristics. They compare and contrast the characteristics of graphite and charcoal in subsequent lessons and extend their investigation of carbon-based substances with a focus on coal and its characteristics, components, and uses.
In the last few lessons of the unit, the focus shifts to other mixtures, namely air and metals. Students create a graphic model of the proportion of various gases that combine to form air. Then, they explore some properties of metals and how they relate to the uses we make of metals. Finally, after a unit full of exploration of substances, student understanding of natural resources is enriched to include how these resources are important and how the personal actions of individuals can help conserve them.