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4. How does structure influence reactivity?

ACCT Admin | Tue, 04/14/2020 - 19:25

“How does structure influence reactivity?” is a question of connection between chemical structure and behavior. The specific ways in which the submicroscopic particles of matter interact with each other and are transformed into different chemical species depend on their atomic composition and molecular structure. The types of atoms present in a molecule and their relative arrangement  in space affect the distribution of the electrons that can participate in bonding processes with other particles. Understanding how molecular structure affects electron distribution, and how this in turn determines how different particles interact and react with each other is critical to design the synthesis of desired materials and to control chemical processes. 

1. What types of matter are there?

ACCT Admin | Tue, 04/14/2020 - 18:53

“What types of matter are there?” is a question of classification. Classification is a very important tool for predicting and explaining the properties of substances in our surroundings. For example, classifying a material as a metal versus a nonmetal allows us to predict that it may conduct heat and electricity quite well. Similarly, identifying a substance as an ionic compound allows us to explain why its aqueous solution conducts electricity. Classifications are often loose categories with gray areas, but they support chemical thinking when seeking to synthesize new substances, determine the identity of a material, or control a chemical process.   

3. What properties of matter types emerge?

ACCT Admin | Tue, 04/14/2020 - 15:22

“What properties of matter types emerge?” is a question of the origin of properties. Predicting or explaining properties of substances often requires analysis of structural rather than compositional aspects of substances, and involves reasoning about emergence rather than arguing based on a central cause. Explaining behaviors of substances involves examining what influences energetic stability and how behaviors on one distance scale emerge from dynamic interactions between structural components on a smaller scale. There are many different scales at which these structure-property relationships are built (from multiple entities in mixtures down to electronic structure). This chemical thinking question is often central to predicting properties of substances, e.g., which oil is best for lubricating a transmission or frying plantains or making soap.

The Rain Puddle

ACCT Admin | Tue, 04/14/2020 - 14:58

A formative assessment designed by an ACCT cohort member designed to investigate student understanding of chemical mechanism.

Balancing with Legos

ACCT Admin | Tue, 04/14/2020 - 14:26

A formative assessment designed by an ACCT cohort member designed to investigate student understanding of chemical mechanism.

2. What cues are used to differentiate matter types?

ACCT Admin | Mon, 04/13/2020 - 22:00

“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.