Most of your students have probably noticed that change can affect familiar objects in their world. For example, they may have watched sugar "disappear" in a glass of lemonade or observed ice melting on a hot summer day. In the STC Changes unit, your students will investigate examples of changes that affect their daily lives..

Initial activities in the unit expand students' understanding of solids, liquids, and gases by exploring changes in state. First, students consider the changes to a single substance - water - as they observe it freeze, melt, evaporate, and condense.

Then, through a sequence of lessons, they investigate changes involving mixture. Student pairs produce mixtures of two solids and of solids with liquids and they observe and compare the changes that result. They also set up "dissolving races" with sugar and water, in which they observe the effects of sugar particle size and water temperature on the rate at which the sugar dissolves.

These activities lead to the discovery that a mixture may be separated again into its individual parts. Students work through several ways of separating mixtures, including: Siving, Evaporation, Filtration, and Chromatography.

Throughout the unit, students observe changes that occur immediately and some that occur over time, and they begin to recognize the characteristics of chemical reactions. They investigate rusting, and they observe and collect the gas formed by mixing an effervescent tablet and water.

At the end of the Changes unit, your students will have several chances to practice their new skills in separating and identifying the components of a mixture. Lessons in which students try ways of separating a mystery mixture, as well as plan and create changes of their own, allow you to evaluate their progress.