11. What are the effects of using and producing different matter types?

“What are the effects of using and producing different matter types?” is a question of consequence evaluation, because chemistry depends on context and affects the human experience. The life cycles of materials, including production, consumption, and disposal, have benefits, costs, and risks in many dimensions. These include social, economic, political, ethical, environmental, and ecological consequences. While the ultimate aim of chemistry is to improve the human condition, the design of chemical processes involves making decisions based on limiting consumption of energy, using renewable resources, and reducing or eliminating production of toxic byproducts. This chemical thinking question is often central to sustainable action work, such as evaluating which refrigerants are better than Freon, or designing a greener battery.

10. How can the effects be controlled?

“How can the effects be controlled”? Is a question that involves making choices about which internal and external parameters to modify to maximize benefits and minimize costs and risks. While outcomes can be predicted based on models, in real processes there are often many variables which cannot be easily controlled, and many conditions that constrain the processes. Feedback loops of testing and refining are often used, resulting in design processes that converge on a desired outcome (maximizing, minimizing, or stabilizing output), usually making tradeoffs among different properties (such as price, quality, safety, and environmental impact). This chemical thinking question is often central to design activities, such as producing biomass or reducing the toxicity of combustion exhaust fumes. 

9. How can chemical changes be controlled?

“How can chemical changes be controlled?” is a question that involves understanding how changes in conditions affect the relative stability of the species involved in a chemical process. Control can be achieved by selecting reactants with structural features that change their energetic stability, varying the concentrations of reactants or capturing and removing products, adding substances which react with intermediates to facilitate or inhibit different mechanistic steps, changing temperature to activate chemical species,, or choosing solvents that facilitate or inhibit certain interactions. For example, controlling the replication of a virus may involve tuning conformations of a substance involved in the replication to block one pathway in the process. This chemical thinking question is often central to chemical process design and analysis activities, such as improving solar cell operation, analysis of battery efficiency, or characterizing the degradation of a dye.