The Mole: Lab Activity
You just got a job working at a factory where they make giant robots. Since the robots
tend to be surly, manipulative, and generally dishonest, it’s a good thing you never get to see the
finished product. Instead, your job is to assemble a little tiny component of the robot that consists
of one bolt, one washer, and one nut. This component is called a “hoozit.” (The hoozit may not
look like much, but it’s very important. It helps the robots dance better.) Each morning, you have
to walk to the hardware bins, get the bolts, washers, and nuts you’ll need for today’s output of
hoozits. To save yourself the trouble of counting out the bolts, washers, and nuts individually,
you are going to measure them out by mass.
Figure 1: The bolt-washer-nut assembly, also known as a “hoozit.”
Part 1 Procedure
1. Using a balance, measure out 15 g bolts, 15 g washers, and 15 g nuts.
2. Take the hardware back to your lab bench and assemble it into hoozits, each containing
exactly one bolt, one washer, and one nut. When you run out of one component, stop.
3. Write down the numbers of bolts, washers, or nuts that you have left over after you
have made your last hoozit.
Part 1 Question
After you made as many hoozits as possible, did you have any hardware left over? Why
or why not?
Part 2 Procedure
1. Return any leftover hardware from Part 1 to the appropriate hardware bins.
2. Obtain fresh batches of bolts, washers, and nuts to make more hoozits. This time, try to
think of a way in which you can make sure that you get the same number of bolts, washers
so that you won’t have any hardware left over. Again, you may not count out individual
bolts, washers, and nuts. You can only measure their masses using a balance.
3. Write down your plan in complete sentences.
4. Carry out your plan.
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Part 2 Questions
Did you have any hardware left over this time?
Did you have more or less hardware left over in Part 2 than in Part 1? Why
do you think your plan worked or didn’t work?
Part 3 Thought Experiment
After less than a week, you quit your job at the robot factory because it is boring and
tedious, and your conscience groans at the thought of helping to make such ill- behaved
androids. Worst of all, one of these robo-jerks has just been made your supervisor. You get a
new job at a chemical laboratory where your first assignment is to react hydrogen and oxygen to
make water. You can’t count out individual atoms of hydrogen or oxygen, but since each water
molecule contains two hydrogen atoms and two oxygen atoms, you decide to measure out 200 g
hydrogen and 100 g of oxygen.
Part 3 Questions
1. Do you think you will have any oxygen or hydrogen left over after you react them to
make water? Which do you think you are more likely to have left over, oxygen or
hydrogen? (Hint: An oxygen atom has eight times the mass of a hydrogen atom.)
2. Can you think of a better way to measure out your oxygen and hydrogen so that you will
not have any of either left over after you react them to make water? Just as in Part 2, you
are only allowed to measure the mass of your hydrogen and oxygen.
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