IONIC & COVALENT
COMPOUNDS
LAB
PURPOSE
To compare the physical properties of ionic and molecular (covalent) solids
HYPOTHESIS
Based on your knowledge, which solid do you think is ionic and which is covalent? Explain
Substance
Type of Compound
Why
Sodium Chloride
ionic
metal and a non-metal
Paraffin Wax
Covalent
Soft, so it must have weaker attraction between molecules
Potassium Carbonate
Ionic
Metal and a non-metal
Cyclohexane
Covalent
Has a prefix in the name, therefore covalent. It is also a liquid at
room temperature, therefore it must have a low melting point
MATERIALS
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Scoopula
Conductivity tester
Well plate
Hot plate
4 test tubes
small beaker
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PROCEDURE
Test tube rack
Distilled water
Sodium chloride (s)
Paraffin wax (s)
Potassium carbonate (s)
Cyclohexane (l) (located in the
fume hood)
Unknown Substance (s)
****No chemicals are to be placed down the drain as they will clog the drain. Use the disposal beaker at the front of the
room. For the waxy substances, allow to cool and scrape contents into the garbage****
1
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5
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9
Create an observation table in which to record data about the odour, hardness, crystalline structure,
melting point, solubility in water and conductivity in water for the 5 substances.
Using the scoopulas, obtain a small amount of each substance into a small beaker to take back to your
station.
Use the wafting technique to make an observation about the odour for each solid.
Use your scoopula to crush to compare for hardness.
Determine if the solid has a crystalline structure by viewing it.
Place a small amount of each solid side by side in a large beaker and put it on the hot plate. Turn on the hot
plate. Observe and record what happens.
Place a small amount of each solid in separate test tubes. Use a pipette and small beaker to take the
distilled water to your lab bench. Add some distilled water. Shake or stir. Record your observations under
“solubility” in water.
Pour some solution from the test tube from step 6 into a separate well on the well plate. Use the
conductivity tester. Record your observations.
Clean your workstation and return all materials neatly (remember not to pour anything down the drain).
OBSERVATIONS
substance
odour
hardness
Sodium
Chloride
no odour
Hard
crystalline
structure
Yes
Paraffin
Wax
slight odour
Soft
No
melting
point
High
Does not
melt
Low
Melts easily
solubility
conductivity
Soluble
Conductive
Not soluble
Not
Floats on top conductive
Potassium
Carbonate
no odour
Hard
Yes
Cyclohexane strong odour
Hard
Yes
Unknown
N/A liquid
no
strong odour
High
Does not
melt
Low
Melts easily
Very low
liquid at
room temp
Soluble
Conductive
Not soluble
Not
conductive
Not
conductive
Not soluble
Forms
bubbles on
top like oil
and water
ANALYSIS
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4
What does a strong odour indicate about the ease with which the particles in the solid leave its surface? Which
type of solid had the strong odour?
A strong odour indicates that particles of a substance can easily leave the surface and float into the air where
they can enter our nose. This suggest that there is a very weak attraction between particles of the substance with
the strong odour. Covalent molecules have weak attractions between molecules, meaning covalent substances
may have stronger odours. The cyclohexane and the unknown substance had very strong odours indicating that
both of these substances are covalent.
What does a low melting point indicate about the bonds between particles in a solid? Which type of solid had the
low melting point?
A low melting point indicates that there are weak attractions between particles in a solid. Covalent substances
have weak attractions between molecules which mean they would have low melting points. In other words it
would take little heat to cause molecules in a covalent substance to separate further apart to form a liquid.
Cyclohexane has the lowest melting point because it was already a liquid at room temperature. The unknown
substance and the wax also had low melting points as they both melted when heated on the hotplate.
Based on your observations, which type of solid was harder? Explain.
According to the observations, sodium chloride, potassium carbonate, and the unknown substance were hard. This
makes sense in that the sodium chloride and potassium carbonate were hard as they are both ionic compounds
because of their make-up of a metal and non-metal. Ionic compounds are harder substances because of their
crystalline structure that is made up of the positive and negative ions tightly packed together. The attraction
between each ionic compound is strong because of the positive and negative charges that exist due to the
exchange in electrons. The hardness of the unknown substance does not make that much sense as it shows more
properties of a covalent bond as opposed to the ionic bond.
From your observations to the above questions, which of the two types of solid (ionic/covalent) seems to have
stronger forces of attraction between the particles?
The ionic solids have stronger forces of attraction between particles because they are the harder solids, have very
high melting points and do not release an odour. Covalent seem to have the weaker forces of attraction between
particles because they are softer, have low melting points and release strong odours.
CONCLUSION
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Briefly summarize your observations
According to the observations, both sodium chloride and potassium carbonate had no odour, were very hard, had
a crystalline structure, high melting points, were soluble and conducted electricity.
Paraffin wax and cyclohexane both had an odour, were soft, had no crystalline structure, had low melting points,
were non soluble and did not conduct electricity.
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The unknown substance had a strong odour, was hard, looked like it had a crystalline structure, had a low melting
point, was non soluble and did not conduct electricity.
Identify each substance as being covalent or ionic (refer to your hypothesis)
According to the above observations, Both sodium chloride and potassium carbonate were ionic due to their lack
of smell, hard structure, high melting points, ability to dissolve in water and conduct electricity. These properties
are present because of the strong attractions between particles due to the give or take exchange of electrons in an
ionic bond which leave both positive and negative charged particles.
Paraffin wax and cyclohexane both covalent due to the odour, softness, lack of crystalline structure, low melting
points, inability to dissolve water or conduct electricity. This is due to the weak attraction between particles in a
covalent bond because of the sharing of electrons that takes place between covalent bonds which leaves particles
with no or very weak positive/negative charges.
The unknown substance had properties of both ionic and covalent compounds. a strong odour, low melting point,
and inability to dissolve in water or conduct electricity leads one to conclude that it is indeed covalent even though
it seemed very hard and looked like it had a crystalline structure.
What did you learn?
I learned how to determine the difference between ionic and covalent bonds by looking at different properties such
as odour, hardness, crystalline structure, melting point, solubility and conductivity. I also learned that ionic
compounds have a strong force of attraction between particles and covalent have a weaker attraction. This is due
to the fact that in ionic compounds, atoms give or take electrons leaving positively and negatively charged
particles. Whereas the covalent molecules share electrons, leaving particles with no charges (or ever so slight
charges).
I also learned that some substances can be a bit confusing and show properties of both ionic and covalent bonding.