2. What cues are used to differentiate matter types?

“What cues are used to differentiate matter types?” is a question of differentiation, or telling matter types apart. Differentiation in chemical thinking is based on the assumption that every chemical substance has at least one differentiating property that makes it unique. Good differentiating properties do not depend on the amount of substance under analysis and have unique values for different materials. Examples include boiling points, solubilities in water, and molecular structure. The characterization of these differentiating properties is critical for the design of methods to separate substances, identify them, detect them in our surroundings, or quantify their amounts.

The Chemical Substances Inventory (CSI) formative assessment was developed by the ACCT team (indicated by the star), and the Rain Puddle formative assessment was designed by a past ACCT cohort member.  

The CSI is a formative assessment tool for learning about how students think about identifying and differentiating chemical substances. It has been tested in middle school, high school, and university chemistry classes. More information about the CSI is freely available in an  in the Jourrnal of Chemcal Education. The CSI Survey itself can be adapted by teachers to use as they wish. Refer to question 2 in each version of the survey to investigate students' chemical thinking regarding the question "What cues are used to differentiate matter types?

The Rain Puddle formative assessment asks students to evaluate four submicroscopic representations of evaporated water and say whether they agree or disagree that each is an accurate representation, and explain why. The focus of this formative asssessment is the process of evaporation as a physical change to matter, in order to make students’ thinking visible regarding how they view what happens to water molecules after evaporation.