New Augmented Reality Applications - Teaching through Multi-User Virtual Environments - page 376

Description of the models
and Developed Structures

and their relationship with ceramics. Finally,
Advanced Chemistry Laboratory teaches about
synthesis, characterization and results according
to their crystal structure.
Spatial structure is key to understanding and
learning pigments. Therefore, using AR in these
classes is important, because it makes a big im-
pact on the students' curiosity, improving their
motivation.
Students may be taking one, two or all three
classes. Students who have attended one class
where pigments were studied can easily deduce
the new aspects taught in the other classes. In our
case, the students that attended a class where AR
was used got actively involved in teaching their
fellow students, improving collaboration.
This methodology provides a successful peer
learning process and improves cooperation. Ad-
ditionally, it allows more students to use the AR
system.

To describe the models developed for the different
classes, we focus on the benefits of using AR in
Inorganic Chemistry education. All models and
structures are designed considering their func-
tionality, what we wanted to teach or explain, and
how the VRML models contributed to them. The
models in this Section are thus described from the
point of view of their importance and contribution
to the classes.
VRML models were developed to understand
and define the crystal structure of solids and,
more importantly, their unit cell. In the case of
metallic crystal structures, a common example is
the Hexagonal Close-Packed Crystal Structure
(HCP). This structure appears when three layers
of spheres are packed as ABA, being A and B
different positions of the layers (see Figure 6a).
The hexagonal unit cell takes six atoms to form
a hexagon and surround another atom in the top
and bottom layers. This unit cell has also another
plane with three atoms in the center of the cell.
In our models, each color represents a different
layer. Note that the arrangement of spheres cre-
ates tetrahedral and octahedral sites. In order to
observe these sites, the spheres in the model are
transparent to a certain degree. Depending on the
position and orientation of the pattern, these sites
are visible or not. For the Body-Centered Cubic
Crystal Structure (BCC) and the Face-Centered
Cubic Crystal Structure (FCC), other models
were developed.
These models help the resolution of problems
and questions related to the unit cell. Examples
are obtaining the volume of an HCP unit cell in
terms of the atomic radius, devising the atomic
packing factor for the FCC crystal structure, and
computing theoretical densities.
In order to learn the crystal systems and crystal-
lographic planes, the structures have been modeled

Case 2: Structural Classification of Silicates
In the case of silicates, their structures and clas-
sification are taught in all three classes. Therefore,
the methodology is slightly different from the
methodology used for the pigments.
First of all, the classification of silicates is
taught using blackboard and PowerPoint pre-
sentations. Then, when students have the basic
knowledge, the AR system is introduced to dis-
tinguish and identify the structures, and to learn
the chemical formula of the compounds, the unit
cell, etc. In this case, we prepare two sessions for
all the students.
Finally, the last week of the semester, before
the exams, the AR system is used to help students
answer questions about silicates, as preparation for
the exam. We have observed that students answer
correctly and quickly to questions that used to be
difficult for them. The results are highly positive.