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Overview
The ChemSense curricular framework highlights collaborative
investigations, representational competence, and chemical change.
ChemSense curricular modules are co-developed by teams of researchers,
developers, and teachers. Each module contains learning objectives,
hands-on experiments, and integrated chemistry tools. See examples
of student and teacher work and sample
curriculum activities.
Key Chemical Themes:
Chemical Change
Our curriculum is designed around a set of five
key time-dependent dimensions that we have identified as
associated with the particulate nature of matter and chemical
reactions: change in (a) connectivity, (b) molecular geometry,
(c) aggregation, (d) state, and (e) concentration. Taken together,
these dimensions begin to portray the molecular world imagined
by chemists to account for observable phenomena. All involve
changes in molecular and supramolecular structure that correspond
to critical aspects of chemical reactivity. In addition, these
time-dependent dimensions cut across more traditional chemical
topics, such as acid-base reaction, electrochemistry, solubility,
kinetics, and thermodynamics. Sample
curriculum activities are available.
Connectivity. The connectivity of atoms to make molecule structures
sits at the core of contemporary chemistry. Chemical identity
is expressed in terms of the molecular structure. Patterns of
observations on many thousands of sophisticated chemical examples
have led to one of the most important advances in chemistry:
the structure-reactivity relationship. Chemical reactions, that
is, the transformation of one set of compounds to another, are
changes in chemical identity and are expressed in terms of connectivity
changes. These patterns of connectivity are often associated
with certain perceptual qualities of a compound.
Molecular Geometry/Shape. Molecular structure involves more
than connectivity; molecules also have shape. And chemical changes
involve more than changes in connectivity. A complete understanding
of chemical reactivity also involves understanding the changes
in spatial relationships that accompany chemical changeÐÐchanges
in shape. Sometimes, changes in shape influence greatly the
understanding of the chemical process. Changes in biochemical
systems are a good example. Other times, the changes take place
and there is no particular impact.
State. The state of a molecule within a set of molecules is
the full inventory of energy relationships that exist. Heat
and light are the two most common sources of energy that influence
changes in state. Phase change is an example, where the relationship
between molecules depends on the temperature of the environment.
When molecules absorb or emit light, this process also involves
a change in state.
Aggregation. The aggregation of molecules is influenced by a
variety of intermolecular and intramolecular interactions. Why
do some salts dissolve in water and others do not? Why do some
things mix while others do not? Forces of aggregation also strongly
influence our understanding of biochemistry because, in general,
multiple molecular units must spontaneously assemble in order
for specific chemical reactions to be catalyzed. An understanding
of drug design, including mode of action, relies heavily on
understanding the relationships that exist in molecular clusters.
Concentration. When materials combine to undergo chemical reactions,
large collections of molecules mix, colliding with one another.
All measures of concentration express "the number of molecules
per unit volume." Changes in concentration affect the number
of collisions that can take place between the different substances.
The higher the concentration, the more molecules of one substance
will be able to collide with those of another. The greater the
number of collisions, the greater the likelihood that a productive
collision takes place. The effect of concentration on reactions
is an important topic in understanding the particulate nature
of matter. |
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