Module: Reaction Rates
DCI: PS1.B (A) Chemical Reactions – Chemical processes, their
rates, and whether or not energy is stored or released can be understood in
terms of the collisions of molecules and the rearrangements of atoms into new
molecules, with consequent changes in the sum of all bond energies in the set
of molecules that are matched by changes in kinetic energy.
PE: HS-PS1-4 Develop a model
to illustrate that the release or absorption of energy from a chemical reaction
system depends upon the changes in total bond energy.
PE: HS-PS1-5 Apply scientific principles and evidence to provide an
explanation about the effects of changing the temperature or concentration of
the reacting particles on the rate at which a reaction occurs.
[Clarification
Statement: Emphasis is on the idea that a chemical reaction is a system that
affects the energy change. Examples of models could include molecular-level
drawings and diagrams of reactions, graphs showing the relative energies of
reactants and products, and representations showing energy is conserved.]
[Assessment Boundary: Assessment does not include calculating the total bond
energy changes during a chemical reaction from the bond energies of reactants
and products.]
[Clarification
Statement: Emphasis is on student reasoning that focuses on the number and
energy of collisions between molecules.] [Assessment Boundary: Assessment is
limited to simple reactions in which there are only two reactants; evidence
from temperature, concentration, and rate data; and qualitative relationships
between rate and temperature.]
The basic content of the standard is as follows.
- All chemical processes can be understood as rearrangements of atoms with resulting changes in energy.
- In another module we focused mostly on changes in total energy. In this module we might want to focus on the unique elements of this particular standard.
- rates of reaction
- collision of molecules
- changes in kinetic energy
- We can pay particular attention the the second Clarification Statement
- evidence from temperature
- evidence from concentration
- evidence from rate
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