Download Lab: Conductivity of Solutions

Lab: Conductivity of Solutions
Background and Notes:
Solutions containing Ions e.g. salts or acid or bases will conduct electricity. Electricity can be simply
defined as moving stream/current of electrons, and we at how solutions/elements can conduct, or transfer
and move, these electrons. Solutions that conduct electricity contain substances (ionic) known as
electrolytes. Solutions that do not conduct electricity contain substances (molecular) known as
nonelectrolytes.
Knowledge and skills:
• Students should understand and know the following terms: Ions in solution, electrolytes,
nonelectrolytes, polar and nonpolar
• Students should be able to test for the conductivity of unknown solutions using a
conductivity apparatus
Fundamental understanding:
• Ions in solution will conduct electricity. Molecular substances do not conduct electricity.
Essential Questions We’re Looking At:
• What substances will conduct electricity in solution?
Questions for you to answer as you do this lab.
1. What is the difference between a cation and an anion? 2 points
2. Draw a small model of a typical crystal lattice structure of NaCl, and label the charges
on the ions in the lattice. 3 points
3. Why is it that an Ionic compound should conduct electricity? What components in an Ionic
Compound help to transfer the electrons? 2 points
4. Will deionized water conduct electricity? Make a prediction/brief hypothesis and state
why you think it will or will not conduct electricity.
5. Directions For Lab: Determine the conductivity of each of the following compounds by using a
multimeter. You are to clean your beakers with distilled water, and then collect 50-60mL of each solution.
You might be required to make the solution: take a teaspoon of a solute you need, mix it with 100mL
of distilled water and mix it until it’s dissolved to develop a solution, that you will be required to
measure.
With a battery (a power supply that supplies electricity – electrons basically), and connecting two
copper wires to each end of the battery into the solution, you will look the stick the black and red
electrode ends of the voltmeter, on the copper wires and see if you see electricity flowing and your
solution is actually conductive (you should get a reading).
Also take note of the units when measuring the voltage, and convert the units to mV (if necessary).
Hypothesize about which ones you think will conduct electricity and which ones won’t. 20 points
Compound/Solution
Distilled water
Tap Water
NaCl Water
Sugar Water
Hydrogen Peroxide
Salt (no water)
Sugar (no water)
Hydrochloric Acid (strong
acid)
Acetone
Isopropyl Alcohol
Copper Chloride
Energy Soda/Drink
Gatorade/ Sports
Beverage
Chemical
Formula
(look up online
to see)
Hypothesis- Is it
ionic? Molecular?
Conducts Electricity? Yes/No. And write
down the voltage.
(write your voltage in volts, not millivolts –
convert if you have to)
Conclusion: 3 points each
1. Which compounds were ionic? Were there any similarities between any of the
compounds that were ionic? (look at their chemical formula)
2.
Which compounds were molecular? Were there any similarities between any of
the compounds that were molecular? (look at their chemical formula)
3.
What did you notice about the conductivity of electricity with plain salt, compared
to when it was dissolved in water?
4.
Electrolytes are essentially salts, which we now know to be conductive to
electricity. But why can’t we taste salty flavors when drinking a beverage
advertised to have electrolytes?
5.
Please list 3 sources of potential errors that could’ve gone wrong during the
experiment. No lab is ever perfect, so just critically think of any minute errors
that could’ve given you a less-than-accurate measurement/result.