Visualizing the Mole

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★☆☆ Minimal safety procedures required

Categories: Chemical Quantities and Calculations

Alternative titles: Visualizing Avogadro’s Number

Summary

Students are shown weighed-out samples of different elements or compounds, each containing one mole of particles. This demonstration helps learners grasp the enormous scale of Avogadro’s number (6.022 × 10^23) by connecting it to tangible amounts of substances.

Procedure

Choose a variety of elements and compounds with different molar masses (e.g., hydrogen gas in a balloon, oxygen gas in a cylinder, water, sodium chloride, carbon, copper).
Calculate the molar mass of each substance.
Weigh out the exact mass corresponding to one mole of the substance (for gases, use balloons or cylinders filled with the molar volume at room temperature and pressure).
Display each sample with a label showing the substance, its molar mass, and its mass or volume for one mole.
Discuss that although each sample has a very different mass or volume, they all contain the same number of particles: Avogadro’s number.

Links

None available

Variations

Show half a mole or a tenth of a mole to make handling safer and easier, while still illustrating proportional scaling.
Include familiar substances such as sugar or table salt to connect with everyday experience.
Use visual props like stacking pennies or counting grains of rice to compare large numbers to Avogadro’s number.

Safety Precautions

Use only small, safe quantities when working with reactive substances.
If gases are included, ensure cylinders or balloons are handled carefully and not near flames.
Label all samples clearly to avoid confusion or misuse.

Questions to Consider

How can very different samples (like 18 g of water and 58.5 g of sodium chloride) contain the same number of particles? (Because the number of moles depends on molar mass, not the physical size of particles.)
What does Avogadro’s number actually represent? (The number of atoms, ions, or molecules in exactly one mole of a substance.)
Why is the mole a useful concept in chemistry? (It links the microscopic world of atoms and molecules to measurable laboratory quantities.)
How does the concept of molar volume (22.4 L at STP, ~24 L at room temperature) apply to gases? (All gases at the same temperature and pressure contain the same number of particles per mole, regardless of identity.)