Science (2015) Grade(s): 09-12 - Chemistry

SC15.CHM.8

Refine the design of a given chemical system to illustrate how LeChâtelier’s principle affects a dynamic chemical equilibrium when subjected to an outside stress (e.g., heating and cooling a saturated sugar- water solution).*

Unpacked Content

Scientific and Engineering Practices

Constructing Explanations and Designing Solutions

Crosscutting Concepts

Stability and Change

Knowledge

Students know:
  • Various stresses made at the macroscopic level, such as change in temperature, pressure, volume, concentration, affect a chemical system at the molecular level.
  • Reaction rates of forward/ backward reactions change with stresses until rates are equal again.
  • Forward/ reverse reactions occur at the same rate in dynamic equilibrium, so chemical systems appear stable at macroscopic level.
  • The egineering design process is a cycle with no official starting or ending point, and, therefore, can be used repeatedly to refine your work.

Skills

Students are able to:
  • Use the engineering design process (ask, imagine, plan, create, improve) to refine a chemical system.
  • Refine a solution to a complex real-world problem, based on scientific knowledge, student-generated sources of evidence, prioritized criteria, and tradeoff considerations.
  • Construct and revise an explanation based on valid and reliable evidence obtained from a variety of sources (including students' own investigations, models, theories, simulations, and peer review).
  • Construct and present arguments supported by empirical evidence and scientific reasoning to support or refute an explanation or a model for a phenomenon or a solution to a problem.

Understanding

Students understand that:
  • Much of science deals with constructing explanations of how things change and how they remain stable.
  • Solutions to real-world problems can be refined using scientific knowledge, student-generated sources of evidence, prioritized criteria, and tradeoff considerations.
  • In many situations, a balance between a reaction and the reverse reaction determines the numbers of all types of molecules present.
  • Criteria may need to be broken down into simpler ones and decisions about the priority of certain criteria over others (tradeoffs) may be needed.

Vocabulary

  • system
  • dynamic equilibrium
  • stresses
  • LeChatelier's principle
  • criteria
  • constraints
  • reversible reaction
  • forward/ backward rates
  • macroscopic level
  • atomic/ molecular level
  • claim
  • evidence
  • reasoning
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