Date […]
Chemistry Lab
Types of Chemical Bonds
Purpose
Test if compounds can be identified as molecular and ionic based on their properties.
Introduction
There are two basic types of chemical bonds in chemical compounds — ionic and covalent. Ionic bonds result
when one or more electrons from one atom or group of atoms transfer to another atom. Positive and negative
ions are created through the transfer. In covalent compounds no electrons are transferred; instead electrons are
shared by the bonded atoms.
The physical properties of a substance, such as melting point, solubility, and conductivity, can be used to predict
the type of bond that binds the atoms of the compound. In this experiment, you will test six compounds to
determine these properties. Your compiled data will enable you to classify the substances as either ionic or
covalent compounds.
Safety
Always wear safety goggles. Call your teacher in the event of a spill or accident immediately.
When you use a candle, confine long hair and loose clothing. Don’t touch heated lab equipment with your bare
hands. Ethanol is flammable. Make sure there are no flames in the room before you use this chemical.
Prelab Questions (complete sentences!)
1) Metallic elements tend to lose electrons and form […]
2) Nonmetallic elements tend to gain electrons and form […]
3) Two examples of ionic compounds are […]
4) A molecule is […]
5) Two examples of molecular compounds are[…]
6) Name and define the type of bond in a typical molecule. […]
7) Would the following pairs of atoms combine chemically to give molecular or ionic compound?
a) Na and F […]
b) C and H […]
c) Ti and Cl […]
d) S and O […]
Material
Part 1
6 vials with chemicals to be tested
tin can lid
Part 2 (do not start until all candles are extinguished)
12-well microplate
pipets
ethanol
ring stand
distilled water
iron ring
candle and matches
conductivity tester
Procedure
Part1
1. Before you begin, write a brief description of each of the six substances in your data table (see below).
2. Place a can lid on an iron ring attached to a ring stand. Position the ring so that it is just above the tip of a
candle flame, as shown in Figure A. Light the candle for a moment to check that you have the correct height.
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3. Place a few crystals of each chemical (sucrose, sodium chloride, phenyl salicylate, calcium chloride, citric
acid, and potassium iodide) in separate locations on the lid, as shown in Figure B. Do not allow the samples
of crystals to touch. Draw a diagram that shows the position of each compound (use numbers).
4. For this experiment, it is not necessary to have exact values for the melting point. The lid will continue to get
hotter as it is heated, so the order of melting will give relative melting points. Light the candle and observe.
Note the substance that melts first by writing a 1 in the Data Table. Record the order of melting for the other
substances.
5. After 5 min, record an n in your Data Table for each substance that did not melt. Extinguish the candle
flame. Allow the tin can lid to cool while you complete the remainder of the experiment.
Part 2
6. Put a few crystals of each of the white solids into a different indentation (well) of your micro plate. Add 10
drops of ethanol to each well that contains crystals. Use a tooth pick to stir the mixtures, but make sure to
wipe the tooth pick clean before moving from one solution to the next to avoid contamination!!!! Record the
solubility of each substance in your data table.
7. Repeat with water: Put a few crystals of each of the white solids into a different unused indentation (well) of
your micro plate. Add 10 drops of water to each of those wells. Use a tooth pick to stir the mixtures, but
make sure to wipe the tooth pick clean before moving from one solution to the next to avoid
contamination!!!! Record the solubility of each substance in your data table.
8. Test the conductivity (ability to conduct electricity) of each water solution in the top row by dipping both
electrodes into each well of the plate. Be sure to rinse the electrodes and dry them with a paper towel after
each test. If the bulb of the conductivity apparatus lights up, the solution conducts electricity. The faster the
light flashes, or even stays on, the more conductivity. Record your results in your data table.
Cleanup and Disposal
9. Clean and dry the micro plate and the can lid thoroughly. Return all equipment and clean your lab bench.
Wash your hands thoroughly before you leave the lab and after all work is finished.
Data Table of Experimental Results
Compound
Description
Order of
melting point
Solubility in
water
Solubility in
ethanol
Conductivity in
solution
(1) Calcium Chloride
(2) Citric acid
(3) Phenyl salicylate
(4) Potassium iodide
(5) Sodium chloride
(6)Sucrose
Conclusion
1) Divide the white substances into two groups according to their properties.
Group A: Calcium choride,…
Group B […]
2) List the properties of each group.
3) Which of the groups consists of ionic compounds and which consists of molecular compounds.
4) State, if you can identify compounds as molecular and ionic based on their properties. [..]
Extention
5) Draw the electron dot structure of
a) N
b) H
c) C
d) Cl
6) Based on the electron dot structure how many covalent bond can each of the atoms from question 5 form?
(same as # of unpaired electrons)
a) N
b) H
c) C
d) Cl
7) Draw the Lewis electron dot structure of the following molecules
a) NH3
b) CO2
c) C2H6O
d) C6H10
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