Course: Chemistry 20
Topic: Testing the Crystalline Structure
of NaCl(s)—cubic or not?
Purpose
Name:
Unit: Chemical Bonding
Date:
Grade: 11
To test images that identify NaCl salt as having a cubic crystalline structure.
1. Background
Draw a picture of NaCl salt using the naked eye and then using a magnifying glass and/or a light microscope. You
will then compare these pictures to ones generated by a scanning electron microscope (SEM) by using the SEM
simulator: Go to King’s College website URL
Predict what the salt crystals should look like under the SEM, compared to the naked eye or some magnifying
technology?
2. Clarifying
Using the SEM simulator go to the following website : Go to King’s College website URL
The salt crystal is known from past investigations and from the simplest 1:1 (NaCl) theoretical structure as being
(face-centered) cubic in nature.
3. Labwork
1. Find the NaCl crystals in the SEM simulation observe and save an image of an NaCl crystal at various
magnifications
2. What is the 3D shape of an NaCl crystal?
3. Is the evidence of sufficient quality to evaluate the hypothesis that NaCl exists with a cubic crystalline structure?
4. Provide an evaluation of the hypothesis that NaCl exists as a cubic crystalline structure.
5. Has the hypothesis that NaCl exists as a cubic crystalline structure been tested sufficiently?
4. Summary
a. Was the SEM needed to view the crystals?
b.
Could a magnifying glass or a laboratory microscope have been just as effective?
c. What other tests might have been more economic? more time-efficient? less technologically
dependent? more environmentally friendly? less collaborative? less fun?
5. Homework
a. In the internal crystalline structure of NaCl salt, is the cubic structure face-centered or body
centered or some other 1:1 configuration?
b. Can we just say that the crystalline structure of salt is cubic or do we have to specify sodium
chloride?
c. Can we use table salt as a substitute for pure sodium chloride; i.e., is table salt a pure substance?
d. How do we know the internal crystalline structure of NaCl salt?
e. What is the origin of this knowledge?
f.
What kind of evidence is used to determine the internal crystalline structure?
g. What kind of knowledge is gathered from the SEM—empirical or theoretical? What kind of
knowledge is used to portray the internal crystalline structure of the salt crystal—empirical or
theoretical?