Vanishing Volume
Structures of Solids
SCIENTIFIC
Introduction
Clearly show the properties of solid crystal structures. Models of closest-packed structures of solids reveal lots of space
between the particles!
Concepts
• Chemical bonding
• Solids and liquids
• Crystal structure
Materials
B-B spheres
Container, transparent, large, rectangular
Beaker or cup, plastic
Styrofoam® spheres, 1”
Safety Precautions
Although the materials in this demonstration are nonhazardous, please observe all classroom or laboratory safety guidelines.
Preparation
Randomly fill the transparent plastic container with the Styrofoam spheres. The spheres represent individual particles
(atoms, molecules or ions) in the structure of a solid. The large plastic container represents the total volume of the “solid.”
Procedure
1. Observe the packing arrangement of spheres within the plastic container. Four different types of packing should be
apparent in the container; they can be distinguished by counting the number of nearest neighbors surrounding specific
spheres or particles. See the Discussion section and Figure 1.
2. Point out the amount of space in the overall volume of the “solid” that is not occupied by the particles.
3. Fill a small plastic beaker or cup with b-b spheres. Observe the volume occupied by the bb’s and note the combined or
total volume of the two sets of spheres before mixing.
4. Add the b-b spheres, which are considerably smaller, to the large container containing the Styrofoam spheres.
5. Observe how the two types of solid particles interact. The small particles fill voids or holes in the structure of the
“solid.”
6. Note that the final volume of the two sets of spheres after mixing is less than their combined volume before mixing. A considerable number of bb’s can be added to the initial “solid” crystal structure without expanding the volume.
Volumes are not additive!
Disposal
None required. Save all materials for future use.
Tip
• This activity may be used in conjunction with other demonstrations to illustrate that volume is not conserved when different liquids are mixed. The most popular example involves mixing equal volumes of ethyl alcohol and water. The combined volume of the two liquids after mixing is considerably less than their initial volumes due to hydrogen bonding.
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Vanishing Volume continued
Discussion
Four types of packing should be visible in the container filled with large Styrofoam spheres. These differ in the number of nearest neighbors surrounding each particle or sphere. (The number of nearest neighbors is also called the coordination number of
a particle.) In all types of packing arrangements of particles, there is still considerable space that is unoccupied. The amount of
space within the volume of a crystalline solid that is actually occupied by particles is referred to as the packing volume or the
packing efficiency. The packing efficiency ranges from 52% of the space filled in a simple cubic structure to 74% of the space
filled in a face-centered cubic or hexagonal closest-packed arrangement. The types of solid crystal structures, the coordination
number, and the space-filling characteristics are listed below:
• Simple cubic, coordination number 6, fills 52% of the space
• Body-centered cubic, coordination number 8, fills 69% of the space
• Face-centered cubic (cubic closest-packed), coordination number 12, fills 74% of the space
• Hexagonal closest-packed, coordination number 12, fills 74% of the space
Simple cubic
Body-centered cubic
Face-centered cubic
Figure 1.
Hexagonal close-packing
When the small bbs are added to the “solid,” they fill up the space left vacant by the larger spheres.
Connecting to the National Standards
This laboratory activity relates to the following National Science Education Standards (1996):
Unifying Concepts and Processes: Grades K–12
Evidence, models, and explanation
Constancy, change, and measurement
Content Standards: Grades 9–12
Content Standard B: Physical Science, structure and properties of matter
Flinn Scientific—Teaching Chemistry™ eLearning Video Series
A video of the Vanishing Volume activity, presented by Jesse Bernstein, is available in Structure of Solids, part of the Flinn
Scientific—Teaching Chemistry eLearning Video Series.
Materials for Vanishing Volume are available from Flinn Scientific, Inc.
Catalog No.
AP2279
Description
Styrofoam® Balls, 1″, Pkg/16
Consult your Flinn Scientific Catalog/Reference Manual for current prices.
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© 2016 Flinn Scientific, Inc. All Rights Reserved.
Vanishing Volume continued
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© 2016 Flinn Scientific, Inc. All Rights Reserved.