IONIC & COVALENT COMPOUND LAB
Name:
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
Ionic/Covalent?
Why?
ionic
metal and a non-metal
Covalent
Soft, so it must have weaker attraction between molecules
Ionic
Metal and a non-metal
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
sodium chloride (s)
paraffin wax (s)
potassium carbonate (s)
cyclohexane (l)
unknown substance (s)
MATERIALS
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Scoopula
Conductivity tester
Well plate
Hot plate
4 test tubes
small beaker
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Test tube rack
Distilled water
Sodium chloride (s)
Paraffin wax (s)
Potassium carbonate (s)
Cyclohexane (l) (located in the
fume hood)
Unknown Substance (s)
PROCEDURE
****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
2
3
4
5
6
7
8
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
sodium
chloride (s)
paraffin wax
(s)
potassium
carbonate
(s)
no odour
Hard
crystalline
structure?
Yes
slight odour
Soft
No
no odour
Hard
Yes
strong odour
N/A liquid
Yes
strong odour
Hard
no
odour
hardness
cyclohexane
(l)
unknown
substance
(s)
melting
point
High
Does not
melt
Low
Melts easily
High
Does not
melt
Very low
liquid at
room temp
Low
Melts easily
solubility
Soluble
conductivity
Conductive
Not soluble
Not
Floats on top conductive
Soluble
Conductive
Not soluble
Forms
bubbles on
top like oil
and water
Not soluble
Not
conductive
Not
conductive
ANALYSIS
1
2
3
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 suggests 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.
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
Substance
Ionic/Covalent?
sodium chloride (s)
Ionic
paraffin wax (s)
Covalent
potassium carbonate (s)
Ionic
cyclohexane (l)
Covalent
unknown substance (s)
covalent
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Why?
Because it is a metal and a non-metal, but also because it
had no smell, was hard and had a crystalline structure. It
also had a high melting point, was soluble and conducted
electricity
Because it was soft, had a slight smell, had a low melting
point, was not soluble and did not conduct electricity
Because it is a metal and a non-metal, but also because it
had no smell, was hard and had a crystalline structure. It
also had a high melting point, was soluble and conducted
electricity
Because it had a very strong smell, had a very low boiling
point as it was a liquid at room temperature, also, it was
not soluble and did not conduct electricity
Because it had a very strong smell, had a low boiling point
was not soluble and did not conduct electricity
What did you learn?
I learned how to distinguish between ionic and covalent substances. I learned that ionic substances have a stronger bond due to the
fact that the elements give or take electrons, leaving charged ions to make up the hard crystalline structure that is hard to break up.
These ionic substances are soluble and can conduct electricity due to the charged particles left after the electrons are exchanged. I
learned that covalent substances have weak bonds because they share electrons and therefore the particles are easy to separate
which allows for strong smells, lower melting points and softer substances.