Name: _________________________________________
Date: ____________________
Measuring the Impossible
An Introduction to the Mole
In order to earn a 4 in the daily work category for science you need to complete a
minimum of 5 extra credit activities per semester. This is due by the end of the semester
however; it may be turned in at any time.
Scientists have measured objects that seem impossible to measure. We know the
diameter of a proton, the speed of light, and the size of the visible universe. Each is impossible
to measure directly, so scientists have developed ingenious methods for measuring them
indirectly. For example, it would be impossible to accurately measure the thickness of one piece
of paper with a ruler. However, you could measure a stack of paper and then mathematically
determine the thickness of one sheet of paper.
This is similar to calculations chemists do. It would be impossible for us to directly
measure the mass of one atom of carbon. We can, however, find the mass of a large number of
carbon atoms and then figure out the mass of a single atom. Because atoms and molecules are
so small, chemists created a quantity called a mole that represents a large number of atoms. A
mole is a quantity, just like the quantity a “pair” represents 2 items and a “dozen” represents
12 items a “mole” represents 600,000,000,000,000,000,000,000 items. That big number can be
represented in scientific notation as 6 x 1023.
The mole is the number of atoms that have a mass (in grams) equal to the atomic mass
found on the periodic table. For example, an atom of carbon has a mass of 12.011 atomic mass
units (amu). A mole of carbon therefore, has a mass of 12.011 grams.
Materials:
1) A balance (if you don’t have access to one you can make one for extra credit – see Building Your
Own Balance)
2) Periodic Table
3) Water, Sugar, Salt, Baking Soda
4) Sand (optional)
5) Calculator
Procedure: In this activity you will see what a mole of a substance looks like.
1) The periodic table tells you the mass of a mole of each element. For example, the mass of a
mole of carbon is 12.011g. To find the mass of a compound, you simply add up the masses of
each element that makes up that compound. For example, to find the mass of a mole of calcium
carbonate (CaCO3) you would calculate 40.078g + 12.011g + (3 x 15.999g) = 100.086 grams.
2) Please calculate the mass of a mole of each compound listed in the data table below.
3) Use your balance to measure 1 mole of each of the substances listed in the data table below.
a. Your balance most likely is not sensitive enough to measure to the thousandth of a
gram. Please round your final mole calculation to the nearest whole number.
4) After you have measured a mole of each compound please describe how much of each makes
up 1 mole (for example, about a bucket full of sand or approximately 150 mL of water).
a. If a mole of a substance is very large, you may measure half of a mole or one-tenth of a
mole and then describe what a full mole would look like.
Data:
Compound
Water (H20)
Salt (NaCl)
Sugar (C6H12O6)
Baking Soda
(NaHCO3)
Optional:
Sand (SiO2)
Calculated mass
of 1 mole (g)
Show Your Work
Description
Conclusion: Please answer these questions in complete sentences.
1) Which would have more mass, a mole of sodium chloride or a mole of potassium chloride?
Why?
2) What is the mass of 1 molecule of sugar? Show your work.
3) Both mass and moles measure matter. How are they different?
4) Density is a ratio between an object’s mass and volume. Which of the compounds listed in the
data table is the densest? Which is the least dense? How did you determine your answer?