Ionic and Molecular Substances Lab
Purpose:
The purpose of this lab is to compare the solubility in water, and the conductivity of substances,
both ionic and molecular.
Hypothesis:
In my educated opinion, I would have to assume that the ionic substances will conduct the
electricity much better. The reason I say this is due to the fact that ionic substances consist of a metal,
and a non metal element. And as you may know, metal is a very strong conductor of electricity. If my
hypothesis is correct, this should make the substance very conductible.
This would mean that the molecular substances would not have as much as a success rate at
conducting the electricity, because it is lacking the metal particles elements. Again, this is just a
hypothesis.
Dependent/ Independent Variable:
In this experiment, the dependent variable would be the powder, because it depends on the
water to change it. Therefore, the water is the independent variable.
Apparatus:
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Ionic substances:
Salt (NaCl)
Potassium chloride (KCl)
Copper (II) sulphate (CuSO4)
Molecular substances:
Glucose (Simple sugar)
Starch
Oil
Watch Glass
Stir rod
Conductivity Tester
Sample Beaker
Wooden splint
Distilled water
Bottle
Waste beaker
Paper
Procedure:
1.
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4.
Create a toonie sized puddle of distilled water on the watch glass.
Place a small amount of the sample substance on the wooden splint, and add to water on glass.
Use glass stirring rod to mix the water and the sample. Mix until it is as dissolved as possible.
Use the conductivity tester to find out if water and sample mixture conducts electricity. Record
observations.
5. Empty mixture into waste beaker, rinse and dry the conductivity tester, watch glass, and stir rod.
Observations:
Substance
Name
Salt (NaCl)
Potassium
Chloride (KCl)
Copper (II) Sulfate
(CuSO4)
Starch
Glucose (Simple
Sugar)
Oil
Unknown
Substance A
Unknown
Substance B
Type of
Substance
(Ionic/Molecular)
Ionic
Ionic
Solubility in
Water
Conductivity Test
Observation
Conductivity
Overall
Dissolved well
Dissolved well
Light on steady
Light on steady
Very well
Very well
Ionic
Partially dissolved
Light on steady
Very well
Molecular
Molecular
Partially dissolved
Dissolved well
Light off
Light off
Did not conduct
Did not conduct
Molecular
N/A
Did not dissolve
Dissolved well
Light off
Light off
Did not conduct
Did not conduct
N/A
Dissolved well
Light on steady
Very well
Results:
From this experiment, I have received most of the information that was needed. I had taken
note that the salt, the potassium chloride, the copper (II) sulfate, and the unknown substance (B) had
conducted very well, and all of their lights for the conductivity test were lit steadily. All of those but the
copper (II) sulfate had dissolved very well. I had also noticed that the starch, the glucose, the oil, and the
unknown substance (A) had not conducted at all, and their light for the conductivity test had not shown
whatsoever. It is interesting that the ionic substances had conducted electricity extremely well, and the
molecular substances hadn’t, just as I had predicted.
Error Analysis:
In this experiment, the only thing that could have been a major variable that we could have
messed with would be one of two things. Either not cleaning the apparatus well, or not stirring the
substances for long enough/ stirring the substances for too long.
Discussion:
1. The solubility for the ionic substances was very strong, most of the samples dissolved right into
the water. When they are dissolved in the water, from what my observations have shown, the
conductivity is extremely strong.
2. For most of the molecular substances, unlike the ionic, most of the substances did not dissolve
into the water. Although, when they were in the water, they did not conduct any electricity.
3. Based on my answers to question one and two, I assume that I can use the conductivity
properties to determine if the unknown compounds are ionic or molecular by noticing if they
conduct electricity at all. If it is an ionic compound, it will conduct, but if it is a molecular
compound, it won’t.
4. By my observations, and my knowledge that I have obtained during this lab, I can solve that
substance B is ionic, and is the potassium bromide, and substance A is molecular, and also
sucrose.
Conclusion:
From this lab, I have learned that Ionic compounds are very conductible, and usually very
soluble, but on the other hand, I have learned that molecular compounds are not conductible, and
usually don’t dissolve into water easily. My hypothesis had turned out to be correct.