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Practical Labs that Work for Grade 11 and Grade
12 Chemistry: Properties of Liquids and
Properties of Solids Labs
««« By John Dragert
John Dragert is a teacher at Stouffville District Secondary School in the York Region
District School Board. He has been teaching for 7 years in the areas of chemistry and
science. He completed his B.Ed at OISE/UT. For fun, John likes to stay active by
playing sports, camping and dancing. He may be contacted at
[email protected] .
Curriculum Connection: Grade 12 Chemistry.
This lab is an excerpt from a session delivered by
Mr. Dragert at the STAO 2007 conference. The full set of
handouts from his session may be found on the STAO website: http://www.stao.org . The presentation details a
series of three labs to be used in the properties section of
the atomic structure unit of the grade 12 university level
chemistry course.
In this series of chemistry labs, you will have the students
complete “The Properties of Liquids” lab first. The
Properties of liquids Lab is intended to review the idea
first taught in grade 11, of using electronegativity values
to rate bonds within molecules as covalent, polar covalent
or ionic. The lab then extends into using the bond types to
identify intermolecular forces between the molecules and
asks the students to use that information to explain the
properties tested in the lab. To help identify the intermolecular forces, the students can refer to a chart on page 195
of the McGraw Hill Ryerson Chemistry 12 textbook.
This “Properties of Liquids” lab leads into a “Properties of
Solids” lab, which may be found on page 202 of the
McGraw Hill Ryerson Chemistry 12 textbook. The students
will practice the same analysis using solid samples. The
students refer to a chart on page 201 of the textbook to
help them with their analysis. This lab was not developed
Practical Labs that Work
by me, and is copyrighted by the McGraw Hill authors for
that section of the textbook.
The sequence culminates in the evaluation lab where the
students analyze a set of five unknown solid samples; A, B
C, D, or E. There are 15 sets, so a group could receive
samples 1A, 1B, 1C, 1D, 1 E or 6A, 6B, 6C, 6D and 6E or
another set. The students first have to use their observations to determine the type of solid represented by each of
the 5 samples; non-polar covalent, polar covalent, network
solid, ionic or metallic. They match up their observations
with a chart on page 201 of the textbook. They then are
given the names and the formulae of each sample according to a key that the teacher has (see figure 1). The formulae are not given in the correct order. The students have to
use electronegativity values to identify the type of solid
represented by each formula and match it up to the
correct sample A, B, C, D or E. Now they have the name
and solid type for each sample.
Safety note
Due to the melting point test, the plastic samples in the
key need to be replaced with alternatives which would still
be non-polar molecular solids. The plastics tend to burn
and produce very bad smelling, irritating fumes. This was
a problem in our lab, even in our brand new school with
state-of- the-art ventilation.
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It takes about seven days to have the students complete
the whole sequence from the properties of liquids through
both properties of solids labs. I am sure it could be
shorter if some of the labs are done as demonstrations.
However, the expectations surrounding intermolecular
forces and properties of materials are very abstract and
hard for even grade 12 students to grasp. We have found
that the properties labs are the most effective way of
teaching these expectations. Without the labs I don’t
believe the students would have a chance at grasping the
concepts. Even with the labs they still find it tough.
With the exception of the one McGraw Hill lab, the rest of
these were developed by me. The “Properties of Liquids”
lab is not intended as an evaluation, but rather, just a
practice. If you would like further information on these
labs, please feel free to contact me at
[email protected] .
Properties of Liquids Lab and Properties of Solids Labs
Objectives
Expectations Covered
1. To allow students to practice calculating DE.N. with
specific molecules
1. Predict the polarity of various substances using
molecular shape and the electronegativity values of
the elements of the substances.
2. To allow students to practice using the DE.N. calculations to identify the bond types and intermolecular
forces present in various liquids.
3. To give students experience with concrete examples in
order to help them understand the ideas of intermolecular forces more completely.
4. To give students the chance to apply the knowledge
gained by completing the first three objectives, to
explaining the properties of various materials.
2. Explain how the properties of a solid or liquid depend
on the nature of the particles present and the types of
forces between them.
3. Conduct experiments to observe and analyze the
physical properties of different substances and to
determine the type of bonding present.
Further information on Three Labs For the Atomic Structure Unit
The atomic structure unit requires the teaching of the
following ideas:
a) Electronegativity
b) ∆ E.N. and bond type (Covalent, Polar Covalent and
Ionic)
c) Strength and characteristics of different bonds
d) Intermolecular forces
e) Properties of materials based upon the bond types
present in the molecules and the intermolecular
forces holding molecules together.
Practical Labs that Work – Page 2
These are complex and abstract ideas that are hard for the
students to understand. Lab exercises are great teaching
tools. Labs give the students real experiences and
concrete examples to help them work through these
complex ideas. In this presentation is a suggested
sequence of three labs:
1) The Properties of Liquids Lab
2) Lab 4-A Properties of Substances McGraw Hill,
Chemistry 12, Page 164
3) The Properties of Solids Lab. This is the Culminating
lab for the unit.
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Properties of Liquids Lab
In this lab the students will study various liquids. The
liquids studied are ethanol, water, butanol, 2-methyl-2propanol and vegetable oil. This lab will help students
analyze substances based upon the ∆ E.N. between the
atoms, the bond type and the polarity of the substance.
They will also identify and study the intermolecular forces
3) The students will use what they have learned about
intramolecular and intermolecular forces to explain
the properties of the solid:
i.e. any covalent substances do not conduct electricity
since the electrons are trapped in the bonds. Metallic
substances conduct electricity since metallic bonds
contain loosely held electrons.
present.
•
Lab 4-A Properties of Substances
In this lab, from page 164 of McGraw Hill’s Chemistry 12
textbook, the students will repeat the process with 5 different solids. They will conduct various tests to identify the
substances as non-polar molecular, polar molecular,
ionic, covalent network, or metallic solids.
The Properties of Solids Lab
After completing the previous two labs, the students are
ready for this lab. Here they are given a set of five
unknown solids. There are three main parts to the lab:
1) Repeat the tests from Lab 4-A in order to:
a) Identify the type of solid in each sample
b) Explain what results led them to their
identification
2) Identify the exact name of each compound as follows:
a) The students are given the names and chemical
formulae of all five of their solids in no particular
order from a teacher key (see figure 1)
b) The students will calculate the ∆ E.N. of the
main type of bonds between the atoms in each of
the given names/formulae (see summary page
with results)
c) Using the ∆ E.N., and other information such as
the position in the periodic table of the atoms in
the molecule or any charges in the formula, the
students will match up the names to the solid
type. The students will explain their choices.
Practical Labs that Work – Page 3
•
•
Ionic substances are harder since ionic bonds are so
strong.
Polar substances are fairly hard since the dipole –
dipole Hydrogen bonding forces of attraction are fairly
strong.
The non-polar substances are soft since the molecules
stick to one another with weak dispersion forces.
Polar and ionic substances tend to dissolve in water
due to dipoles and charges that are attracted to the
dipoles in water. Non-polar substances do not have
these dipoles and are not attracted to water.
Properties of Solids lab Example
The student is given 5 solids (see teacher key- figure 1).
Part 1
Solid B is a soft material, with a low melting point that
does not conduct electricity nor dissolve in water.
The student identifies this as a non-polar molecular solid
since these properties match those of a non-polar
molecular solid.
Part 2
The student is told that wax C24H50 is one of their solids.
The student calculates the ∆ E.N.
C
-H
2.55
- 2.20
0.35
The ∆ E.N. shows that the bond is a covalent bond and the
student rates wax as a non-polar molecular substance.
The student concludes that Solid B, the non-polar
molecular substance, is wax.
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Part 1 New Solids
In the same set the student is given solid C and solid D.
Solid C is a shiny substance that is hard, conductive as a
solid, insoluble and hard to melt. Solid D is a black
substance that is hard, nonconductive, insoluble and
doesn’t melt.
Based upon these results, the student identifies solid C as
a metallic substance and solid D as a network covalent
substance.
Part 2
The student is told that coal and tin are two of the solids.
He/she does not need to complete the ∆ E.N. calculations
for the solids. However, he/she remembers from the previous lab, that network solids are made from group 14
elements. Coal is a form of carbon – a group-14 element.
The student concludes that the network solid is coal and
that coal is the identity of solid C. He/she concludes that
tin is the metal, since tin is found in the metal part of the
periodic table. Consequently, solid D is identified as tin.
Possible Wrinkles
In the sets where silicon is used, it is used as the covalent
network solid. Network solids are not supposed to conduct
electricity, but silicon, a metalloid is conductive. This may
confuse it with the metal. However, using an obvious
metallic solid, such as a strip of silver or aluminium in the
same set, will resolve this confusion. As well, by looking at
the periodic table, the student will see that silicon is a
metalloid and therefore able to be a conductor. Don’t mix a
strip of lead in with the set that has silicon as the network
solid.
Definitions and Properties
Non-Polar Molecular Solid
These are molecules that are formed between atoms with
a small electronegativity difference. They are generally
non-conductive, soft, have low melting/boiling points and
are not soluble in water. They possess weak dispersion
forces of attraction.
Polar Molecular
These are asymmetrical molecules formed by atoms with
electronegativity differences between 0.5 and 1.7. They are
nonconductive, fairly hard, soluble in water, and have
medium melting/boiling points. They have dipole-dipole
and hydrogen bonding forces of attraction.
Covalent Network
These are molecules that consist of continuous networks
of covalent bonds. They are non-conductive (exception Si),
very hard, insoluble in water and have high melting/boiling points.
Ionic
These are formed between cations and anions due to
electrostatic attraction. They are soluble, conductive as a
solution, very hard yet brittle, and have high melting/
boiling points.
Metallic
These are formed by metals. They all have a lustre, are
conductive, are insoluble, range in hardness and have high
melting/boiling points.
continued...
Practical Labs that Work – Page 4
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Figure 1: Teacher Key (created by John Dragert)
SCH 4U1
Set Number
1
2
Sample Key for Properties of Solids Lab
A
Al
Aluminum
K3 Fe(CN)6
4
5
7
Potassium Iodide
Polystyrene
Zn
Zinc
Na2S2 O3
C
Coal
Polyvinyl
Alcohol
Polyethylene
KI
C12 H22 O 11
Sucrose
FeS
Iron (II)
Sulfide
KCl
Potassium Iodide
6
Butyne-1,4diol
Polystyrene
Potassium Chloride
8
Na2S2 O3
9
FeS
Iron (II)
Sulfide
Butyne-1,4diol
10
11
12
13
Mica
(Silicate Rock)
Rubber
NaCl
Sodium Chloride
14
15
C
Urea
SiC
Silicon Carbide
Potassium
ferricyanide
3
B
KI
Sn
Tin
C12 H22 O 11
Sucrose
Al
Aluminum
C6 H12 O6
Glucose
Paraffin Wax
Zn
Zinc
Si
Silicon
Orthoclase
(Silicate Rock)
KCl
Potassium Chloride
Polyethylene
Atomic Structure Unit
D
Mica
(Silicate Rock)
C12 H22 O 11
Sucrose
E
S8
Sulfur
Sn
Tin
NaCl
C6 H12 O6
Glucose
Rubber
Sodium Chloride
FeS
Iron (II)
Sulfide
Ag
Silver
CuSO4
Copper (II) Sulfate
Orthoclase
(Silicate Rock)
Si
Silicon
K3 Fe(CN)6
Al
Aluminum
Si
Silicon
Sn
Tin
Polypropylene
Cr
Chromium
Paraffin Wax
Polyacrylamide
Polyethylene
Polyethylene
Potassium
ferricyanide
C12 H22 O 11
Sucrose
Zn
Zinc
Sn
Tin
C
Coal
Potassium Iodide
KI
KI
Polyethylene
Urea
CuSO4
Al
Aluminum
S8
Sulfur
Polypropylene
Potassium Iodide
C12 H22 O 11
Sucrose
Polyvinyl
Alcohol
SiC
Silicon Carbide
Al
Aluminum
Copper (II) Sulfate
Zn
Zinc
Polyacrylamide
KI
Potassium Iodide
FeS
Iron (II) Sulfide
Notes
1)
The Polymers and rubber tend to burn in the melting point test releasing irritating fumes. These should be
replaced with other non-polar molecular solids. A large organic acid such as Lauric Acid will work. Even though it
has a polar acid group, the large covalent end will make act like a non-polar molecular solid.
2)
FeS is a network solid. This is despite the fact that neither of the atoms is in group 14. The McGraw Hill
Ryerson definition of a covalent network solid states that these solids usually contain group 14 elements. To avoid
the confusion, any form of quartz rock (SiO2) can be used instead as Si is in group 14. As well, you could substitute
coal, silicon or Silicon carbide for FeS.
3)
Solid Silicon is a covalent network solid. These types of solids are not supposed to conduct. However,
silicon does conduct. Point the students to the position of Silicon on the periodic table to help with the confusion.
Silicon is a group 14 element so it should form covalent network solids. As well it is a metalloid, which explains
the ability of silicon to conduct.
Practical Labs that Work – Page 5
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Student activity
Lab: Properties of Liquids
Purpose
To determine the properties of various liquids and explain
them using Intermolecular forces and bond types.
Hypothesis
The type and strength of intermolecular forces and bonds
will determine properties such as solubility, sensitivity to
electric charges, and melting/boiling points.
Materials
•
•
•
•
•
•
•
Methanol*
Ethanol
Butanol
Dodecanol
Distilled water
Vegetable Oil
Ice
•
•
•
•
•
•
•
Food Colouring
Ebonite Rods
Fur/cotton
Test Tubes
1 Burette
1 Large beaker
1 400 mL beaker
Note from the STAO Safety Committee
Methanol is toxic. It can cause blindness. For this reason,
goggles MUST be worn. Ethanol, if denatured Ethyl
Alcohol, contains methanol. Boiling alcohol is not a safe
activity and therefore this lab should be run as a demonstration at the teacher’s desk. Each group can run one
liquid, under the direct supervision of the teacher.
Procedure
Electrical Sensitivity Test (or Electrostatics)
1. Half fill a burette with water. Place a large beaker
below it.
2. Place a static charge on the ebonite rod.
3. Open the burette to get a fine stream of water flowing
into the beaker
4. Move the ebonite rod close to the stream and record
observations.
5. To test ethanol, drain the burette and repeat steps
1 – 4 with 50 mL of ethanol in the burrette.
6. To test oil, do not use the burette. Instead, take two
beakers. Place 50 mL of oil in one beaker. Pour a fine
Practical Labs that Work – Page 6
stream of oil from one beaker to another. Move the rod
near the stream. Repeat as necessary and record
observations.
Solubility Test
1. Obtain 4 test tubes. Fill each test tube to about 1/3
with water. Place 2 drops of food colouring in each test
tube.
2. Add 2 pipette squirts of liquid to each tube according
to the list (about 4 mL – enough to see a difference
between the liquids).
#1 Methanol
#2 Ethanol
#3 Butanol
#4 Vegetable Oil
3. Record Observations.
Boling Point
1. Half fill a 400 mL beaker with water and place it on a
hot plate.
2. Place 5 mL of ethanol in a small test tube. Hold the
test tube in the water using a clamp attached to a
stand. Place a thermometer in the water.
3. Turn the hot plate to a setting of 5 – 7 in order to heat
the water.
4. Record the temperature at which the ethanol boils.
Record any other observations.
5. Remove the ethanol. Keep heating the water and
record the temperature at which water boils
6. Repeat steps 1 – 4 with Butanol in the test tube.
Freezing/Melting Point
1. Set up a water bath at room temperature and place it
on the hot plate. Place a sample of dodecanol in a test
tube. Place the test tube in the water, record
observations.
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Student activity
2. Increase the temperature of the water by 5°C and
repeat. Keep increasing the temperature of the water
by 5°C each time and repeat until the melting point of
dodecanol is determined.
3. Create an ice water bath in a small beaker. Record the
temperature. You want it to be as close to zero as possible. Place 5 mL of ethanol in a test tube and hold the
test tube in the ice water bath for several minutes.
Record observations.
4. Repeat Step 3 with tert-butanol (2-methyl-2-propanol)
5. Look up the melting point of regular butanol.
Questions
1. Draw the Lewis dot structural diagram for each molecule used in the experiment. On each diagram identify:
i) The type of bond present in each part. Label any
charges or partial charges present on the
diagram.
ii) Any polar parts and any non-polar parts of the
molecule
iii) The type and strength of any intermolecular
forces that could be present in each part of the
molecules.
2. a) Draw the hydrogen bonding that is present in water
(draw at least 3 molecules bonded together).
b) Draw the hydrogen bonding that is present in
ethanol. How many molecules can you join together?
Practical Labs that Work – Page 7
c) What difference do you notice about the hydrogen
bonding in an alcohol vs. the hydrogen bonding in
water?
d) Why is it technically incorrect to call hydrogen
bonding hydrogen bonding? Is it really a bond? If not
what is it? Is it as strong as an ionic, polar covalent or
covalent bonds? Explain.
e) Why do you think that they call it a bond? (Hint think
about the strength of hydrogen bonding compared to
other dipole forces)
3. Use the results from questions 1 and 2 to answer the
following:
a) Explain the electrical sensitivity results.
b) Explain the solubility results.
c) Explain the boiling point results.
d) Explain the freezing/melting point results.
Conclusions
State:
i) Generally, what type of materials are sensitive to
electricity, and dissolve in water.
ii) How intermolecular forces increase the boiling/melting points of materials.
iii) Even though they are weak forces, how dispersion
forces can sometimes be stronger than other forces.
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These pages give a summary of the Typical Results for the Properties of Liquids lab. The summary refers back to
Table 1 below, for the ∆ E.N. calculations and the rating of the different bonds.
TABLE 1: ∆ E.N.
0
0.5
Covalent
1.7
Polar Covalent
4.0
Ionic
Table 1: ! E.N., Bond Type and Charge Type
Material Main Bond
! E.N.
Bond Type
Oil
C-H
Water
O–H
Ethanol
C–C
C–H
C–O
O–H
Practical Labs that Work – Page 8
2.55
-2.20
0.35
3.44
-2.20
1.24
2.55
-2.55
0.00
2.55
-2.20
0.35
3.44
-2.55
0.89
3.44
-2.20
1.24
Charge
Type
Which
Atom Is
+
-
Covalent
None
N/A
N/A
Polar
Covalent
Partial
H
O
Covalent
None
N/A
N/A
Covalent
None
N/A
N/A
Polar
Covalent
Partial
Charges
C
O
Polar
Covalent
Partial
Charges
H
O
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Electrical Sensitivity (Electrostatics Test)
Boiling Point Results
•
Water: Water is a polar substance with partial
charges. The ebonite rod is negative. The positive
partial charges on the hydrogen atoms in the water
are attracted to the rod.
•
•
Ethanol: Ethanol is a substance with a polar OH group
on the end. The ebonite rod is negative. The positive
•
Water Butanol: Water can H – Bond on both sides
and Butanol only on one side. However, Butanol has a
longer carbon chain than Ethanol. The extra
dispersion forces add up to hold Butanol molecules
together even more strongly than water.
partial charges in the ethanol will be attracted to the
rod.
•
Ethanol Water: B.P. increases. Ethanol can H – bond
on one side, whereas water can H – bond on both sides.
Therefore water molecules are held together more
strongly.
Oil: The main bond type in the oil is the non-polar
C – H bond. It is not attracted to the rod.
Melting/Freezing Point Results
•
Note: There are polar C – O bonds in the oil. In small
drops these can interact with the rod. Therefore this
test is best done with a thick stream rather than in a
burette.
•
Ethanol Butanol Dodecanol: M.P. increases due
to the extra CH2 groups. This causes an increase in
the dispersion forces that adds up to hold the molecules together more strongly. More energy is needed
to break them apart.
Solubility
•
Table 1 can be repeated for all of the alcohols, but the
result will be the same as Ethanol.
•
Methanol and Ethanol will dissolve in water. They have
a polar O – H bond with partial charges that will be
attracted to partial charges in the polar water and will
cause the molecule to dissolve.
•
In Butanol, the non-polar side is long enough to pull
the molecule out of the water, despite the polar O – H
bond.
•
In oil, the vast majority of the bonds are non – polar.
Therefore it will not dissolve.
•
Ethanol and 2 – methyl – 2 – propanol: Ethanol won’t
freeze in the ice water bath, but 2 – methyl – 2 –
propanol will become slushy. This is due to the
arrangement of the OH groups in the propanol. They
are arranged to H – Bond better and thus hold the
molecules tighter than the OH groups in Ethanol.
Therefore 2-methyl-2-propanol will freeze at a higher
temperature than Ethanol.
Boiling Point and Freezing/Melting Point
Table 2
Substance
Ethanol
Water
Butanol
Dodecanol
2-methyl-2-propanol
Boiling Point ºC
78.0
100.0
117.3
255.0
82.2
Practical Labs that Work – Page 9
Freezing Point ºC
- 117.0
0.0
- 89.5
+ 26.0
+ 25.5
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Student activity
Lab: Properties of Solids
Introduction
In this unit you have learned about atomic orbitals, molecular orbitals, electronic configuration, molecular shapes,
bond types, intra and intermolecular forces of attraction
and properties of liquids and solids. Today you will test
different unknown solids to identify the type of solid and
identify the actual compound using a key. You will then
explain the properties of each solid using the knowledge
you’ve gained during the unit.
Purpose
Write your own using the introduction.
Hypothesis: (Pick one of the following two possibilities
for your hypothesis)
a) State whether you think that you will be able to identify the types of solids you have and how you think you
will be able to do this. Or,
b) Take a brief look at all of your samples. Take an educated guess at the type of compound represented by
each sample. Give one reason to support each guess.
Materials
Decide on the test you will need to use and list all materials you will need. You can make this list up as you go
along. Note the following:
i) For every chemical you use you do not need to give
the amount. That will be done in the procedure;
ii) You will need to give the concentration, if
applicable, and the name
Example: 1 molar HCl or Zinc Metal powder;
iii) For each type of equipment used you will need to
give the number of pieces used and the size, if
applicable.
Example: 1 scoopula or 4, 250 ml beakers;
Practical Labs that Work – Page 10
Also, put the list as a series of short 4- or 5-line columns
____________
____________
____________
____________
____________
____________
____________
____________
____________
____________
____________
____________
Procedure
Write a step-by-step procedure for the lab. Write it as if it is
a recipe and I am an inexperienced person who doesn’t
know what I’m doing. Write it so I could repeat the experiment without you there to explain it to me. Include the
amounts of substances used. For example if you are using a
small scoop, then write “take a small scoop.” If you are
using 2 grams, write “take 2 grams.” At every step where an
observation is taken, write “record observation” in that step.
Observations
Create a chart for your observations. Remember to decide
the number of tests you are going to do and how many
chemicals you are going to test. One will set the number of
columns and the other will set the number of rows.
Discussion
1. For each type of solid on page 201 of the McGraw Hill
Ryerson textbook, answer the following. You may also
use the preceding pages in the textbook:
a) Give a proper definition of each type of solid: Nonpolar molecular (Covalent molecular), Polar molecular, Covalent network, Ionic solid, and Metallic.
b) Identify and describe the key properties of each
type of solid.
2. For each sample in the lab, answer the following:
a) Correctly identify the properties of the solid sample
and use the properties to identify the type of solid it is.
Properties include; hardness, solubility in water, conductivity in water, conductivity as a solid, and melting
point.
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Student activity
b) Once the type of solid has been identified, use your
c) For further help, use the position on the periodic table
knowledge of that solid to explain: the hardness of
each sample, the melting point of each sample, the
solubility of each sample and the conductivity of each
sample.
of the atoms in your compounds. For instance compounds with atoms in group 14 on the table are likely
(not always) network solids.
4
3. Your teacher will provide you with the name and formula of each of the samples in your set. They will not
be in order. You will have to use the formulae given to
you and the information from #2 to identify the names
of the compounds in your set as follows:
a) Calculate the electro-negativity difference (DE.N.)
between the atoms in each bond in the compounds.
Use this information to rate the bonds in the solid and
determine the type of solid represented by each formula given.
b) Match the type of solid determined for the formulae in
part A above with the type of solid that you determined
for each sample in question #2. Now you will have the
name and formula for each sample in your set.
Practical Labs that Work – Page 11
a) Why would wax (a non-polar molecular solid) or salt
(an ionic solid) be a poor a poor choice for the outside
of a building while bricks (made of clay and sand, both
network solids) would be a better choice?
b) Use the electronic configuration and the number of
electrons available to bond in order to explain why
iron is a much stronger metal than copper and is a
better a choice for making bridges and buildings. In
your answer, draw out the electronic configuration for
each metal. Identify the number of electrons available
to bond in each metal based upon the electronic configurations. Use this to explain why iron is the
stronger metal.
Conclusion
State the identities and type of solid for each sample
tested.
Volume 40 • 1 September 2008