Contributed by: Council of Chief State School Officers (CCSSO)
Criterion 1:
Student must state another factor that affects solvation rate besides
temperature and must test this factor. The test must include a control.
There must be at least two tests that differ by that factor only within
the collection of tests in question 1. The tests however do not need
to be correct concerning increasing or decreasing solvation rate though
this may affect question 2. Examples of factors: stirring, amount
of water, amount of sugar, crushing sugar cube, or purity of water.
Criterion 2:
Student must test the effect of temperature on solvation rate. This
test must include a control, which means there must be at least two
tests that differ only by the temperature in the collection of tests
from question 1. The results don't have to indicate that temperature
increases solvation rate, or, the student correctly tests an additional
factor from criterion 1.
Criterion 3:
Student must state in question 2 a correct reason for temperature
increasing solvation rate. The reason must include something about
increasing the energy of water or sugar molecules or the speed of
the water or sugar molecules or viable explanation for an additional
factor from criterion 4 is given. Examples:
1. The water molecules are moving faster.
2. The heat increased the KE of the sugar molecules.
Criterion 4:
Student must state a correct reason for the factor they came up with
affecting the solvation rate in question 2. The reason must include
whether the rate increased or decreased and why (if solvation rate
increase, reaction time decreases and vice versa).
Examples:
factor |
effect on rate |
explanation example |
stirring |
increase |
keeps water mixed and homogeneous, keeps water
going by sugar, keeps concentration around sugar lower |
amount of water |
increase |
concentration lowered, more water molecules to
react with |
amount of sugar |
increase |
more sugar molecules ro react |
crushing sugar cube |
increase |
more surface area of sugar, more sugar molecules
exposed |
concentration of water |
decrease |
fewer water molecules free to react |
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