All
of the experiments must be done in the presence
of a parent or teacher.
Experiment
2: The Effect of Particle Size on Rate of
Reaction
Ideas | Materials | Procedure | Observations | Summary | Questions
| Ideas |
|---|
|
The rate of a chemical reaction
is affected by the physical size of
the reactants. Decreasing the size
of the particles which make up a given
weight will increase the number of
particles represented by the same
weight. Smaller particle size results
in an increase in the rate of reaction
because the surface area of the reactant
has been increased.
My predictions:
The powder will react _______ times
faster than the whole tablet.
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| Materials |
|---|
|
Note: All experiments should be
done using original formula effervescent
Alka-Seltzer.
- 3 Clear glasses
- 3 Alka-Seltzer tablets
- Mortar and pestle
- Stopwatch
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| Procedure |
|---|
|
A. Whole Tablet
1. Fill a clear glass with exactly 8 oz. of room
temperature or lukewarm water.
2. Drop 1 whole Alka-Seltzer tablet into the
water. Measure and record the time to dissolve.
B. Tablet Broken into ~8 Pieces
1. Place 1 Alka-Seltzer tablet onto a sheet of
paper and break into approximately 8 pieces of
about equal size.
2. Fill a clear glass with exactly 8 oz. of room
temperature or lukewarm water.
3. Slide broken tablet into the water from the
sheet. Measure and record the time to dissolve.
C. Powdered Tablet
1. Place 1 Alka-Seltzer tablet into mortar and
grind to a fine powder.
2. Transfer powder into a clear cup. (Note: It's
important to have the powder in the cup before
adding water.)
3. Add 8 oz. of water to the glass. Measure and
record the time to dissolve.
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| Observations |
|---|
|
Particle Size Time for Reaction to be Completed
Whole Tablet _________ Seconds
8 Pieces _________Seconds
Powder _________Seconds
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| Summary |
|---|
|
a) As particle size decreases, the rate of reaction
_______________.
b) The rate of reaction for the powder was ___________
times faster than for the whole tablet.
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| Questions |
|---|
|
1. As particle size decreases, the total surface
area of a reactant ________________. As a result,
the probability of interactions between atoms/ions
________________, and the rate of reaction ___________________.
2. Particle size appears to have _______________
(less or more) of an effect on the rate of reaction
than temperature.
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