Lab: The Mystery Box
Pre-Lab
Models and theories are used in Chemistry to represent and explain the behavior of particles,
which we cannot see. Read and understand the sections of your textbook covering the
development of early atomic theory, and answer the following questions:
1. Briefly describe the experiment conducted by Joseph John Thompson in 1897. Include
the value related to the electron derived by Thompson.
2. Describe Robert Millikan’s experiment conducted in 1911 and its result. Explain its
significance with the respect to the electron
3. Describe Thompson model of the atom
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4. Describe Rutherford’s gold foil experiment and its results
5. Did the Thompson model of the atom explain Rutherford’s gold foil experiment results?
Explain why.
6. Explain Rutherford’s model of the atom. Did it explain the gold foil experiment results?
Explain why.
7. Given that no one has yet seen the inside of an atom, propose 1 additional experiment and
explain how the expected results would support or disprove Rutherford’s model of the
atom.
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Lab: The Mystery Box
Introduction
In this lab you will develop a theory that explains your experimental results and propose further
experiments to confirm the validity of your explanation.
You will be presented with a closed cardboard box with a funnel showing on top and an outlet on
the bottom. It will be your quest to determine the process occurring inside the box that explains
the behavior that you will observe. Your procedure will involve pouring different aliquots of
water into the funnel and collecting and measuring any water that may come out. After following
the suggested procedure you might try some additional experiments but do not look into the box
or take it apart. You will never be able to look inside the box, even after the experiment.
General Procedure
Carefully follow this procedure because you will not be able to start over.
1.
2.
3.
4.
5.
Start with a 75 mL aliquot of water and take the desired measurements.
Now add additional 75 mL aliquots until no more useful information can be derived.
Then use 150 mL aliquots until more useful information can be derived.
Now add 225 mL aliquots, once again until no more useful information can be derived.
Continue with additional set of aliquots increasing them by 75 mL until no more useful
information can be derived.
During the enactment of the procedure, record all volumes in and our of the mystery box.
Consider recording your results in a table format. You may also want to record the time that it
takes for the first drop of water to come out of the bottom outlet, and/or the total time that it
takes for all of the water to come out, or other measurement. You might graph different sets of
data to help you understand the behavior of the mystery box, such as mL of water output vs. mL
of water input, or time required for the first drop of water to exit at the outlet vs. volume in ml of
each aliquot inputted, etc.
Theory Development
Suggest a theory about what is inside the box that plausibly explains your observations. Could
you think of other ways to test your theory? Propose other experiments you could do to help you
figure out the contents of the box.
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Post- Lab
1. What is your theory? Use a diagram to show the internal construction of the Mystery Box.
2. Report your data here and justify how your theory explains the data that you collected. If it
does not explain all of the data, please specify what is not explained.
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3. Propose a subsequent test/s that you could do to either confirm or disprove your theory. If
your theory does not explain all of the data, make sure to include test/s that would help clarify it.
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Teacher Notes
Acknowledgments
The following NCSSM staff played a part in developing this inquiry based experiment: Dr.
Linda Schmalbeck, Dr. Dr. Myra Halpin, Dr. Marion Brisk, Mr. Guido Gabbriell,i and Cameron
Cook
This experiment promotes the development of inquiry skills by causing the students to deduce the
internal structure of the mystery box from its behavior when water is poured into it. The process
of observation and deduction overshadows the ability of the students to derive the correct
internal design. In this experiment the experience of interpreting data into a coherent theory
represents the major value derived by the students. I recommend strongly that you never show to
the students the internal construction of the mystery box in order to make the inquiry experience
realistic by maintaining a correlation to our inability to see the internal structure of an atom.
This lab works best if it is broken up into 3 time periods:
1. Provide the pre-lab to the students 1 week prior to doing the lab
2. On lab day provide the students at lest 45 minutes to conduct the experiment and collect
data. The equipment required is:
a. 1 Mystery box. See the construction below.
b. 4 graduated cylinders: 2 each of 250 mL and 500 mL. One is used for pouring
and one for catching the water at the outlet
c. Optional equipment: stop-watch, food coloring
3. After the lab, provide the students 1 week to complete the post-lab.
Construct the box as follows:
Begin with a standard size
file storage box with a top.
water in
small funnel
A
B
A
A
Plastic
cup
C
D
water out
Placement of holes in cups should be
approximately made at:
- location A at 160 mL
- location B at 50 mL
- location C at 50 mL
- location D at 50 mL
Plastic drinking straws glued
into holes in plastic cups
Box top
You will need to experiment with the height placement of the lower(B) and higher(A) outlets in
the first cup, because you want the following behavior to occur:
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1. When the students initially add the 75 mL water aliquots, at first some of the water
remains in the top and bottom cups but then eventually (as the lower part of the two cups
is filled) the water input equals the output.
2. The same input=output occurs when 150 mL aliquots are added
3. However, when the 225 mL aliquots are added, because now the amount of liquid
reaches the upper outlet(A) of the cup, some of the water flows in the intermediate cup
and is retained there. Eventually, as more 225 mL aliquots are added, input will once
again equal output.
While most students can design a system explaining the behavior observed in 1 and 2 above, the
apparent anomaly observed in 3, represents the inquiry challenge that the students are asked to
resolve.
Because of different learning styles, some students can design a model based on the tabular
results derived from the experiments, whereas others may need to graph the data in order to
understand the inner structure of the mystery box.
After you have obtained experience with this activity, you may want to experiment with alternate
designs such as this one:
Begin with a standard size
file storage box with a top.
water in
small funnel
B
AA
A
Plastic
cup
C
water out
Placement of holes in cups should be
made:
- location A at 50 mL
- location B at 100 mL
- location C at 20 mL
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Plastic drinking straws glued
into holes in plastic cups
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