Lab: Chemical Bonds
Introduction:
Chemical bonds are combinations of atoms held together by chemical bonds. These chemical bonds
are of two basic types- Ionic and Covalent. Ionic bonds result when one or more electrons from one atom or
group of atoms are transferred to another atom. Positive and negative ions are created. In covalent
compounds the bonded atoms share the electrons.
The curls and waves in your hair are the result of many hydrogen, ionic and covalent bonds between
the chains of atoms that make up each hair follicle. Styling hair by wetting it or heating it with a curling iron, is
an attempt to change the hydrogen bind and the ionic binds so they will form a new shape. The changes are
temporary and as soon as you wash the hair the style is gone. The solutions in a “permanent” however, break
and reform covalent bonds. A permanent wave does not wash out when you shampoo your hair.
The physical properties of a substance such as melting point, solubility, and conductivity tell us a lot
about the type of bond in a compound. In this experiment you will conduct tests on these properties and
compile data enabling you to classify compounds as ionic or covalent.
Purpose: To learn the properties of ionic and covalent compounds.
Equipment:
 Hot plate
 Pan
 Potassium iodide
 Sodium chloride
 Sodium carbonate
 Salicylic acid
 Benzoic acid
 Paradichlorobenzene
 Distilled water
 6 test tubes
 Conductivity device
 Test tube brush
#1
#6
#2
#5
#3
#4
Procedure:
1. Observe and record the description of each substance
2. Place a few crystals (not a heap or mound) of each of the six compounds listed above at separate
locations on the pan (do not allow the samples to touch). Place the pan on the ring stand and heat
the substance up using a candle. Record if the substance melted “m” if the substance did not melt
record “nm” in the data table). Extinguish the flame
3. Place a few crystals of each of the white solids in to separate small test tubes. Fill each test tube to
the top with distilled water, shake well for one minute (rinse stopper between test tubes). Record
an “s” for substances that dissolve and an “ns” for substances that are not soluble.
4. Test the conductivity of each water solution by dipping both electrodes in the test tubes. Be sure to
rinse with the electrode distilled water and dry them between each test run. Look at the light
combination and the back of the tester to see if the substance is conductive or not. Record your
observations. Clean the test tubes well using the test tube brush if necessary.
Data Table:
Properties
Substances
Description
Melting point
Solubility
Benzoic Acid
Paradichlorobenzene
Potassium Iodide
Salicylic Acid
Sodium Carbonate
Sodium Chloride
Post Lab questions:
1. Group the substances into two groups based upon the properties.
Group I
Group II
2. List the properties of each group.
Group I
Group II
3. Label each group ionic (conductive, loud beep) or covalent
Group I
Group II
4. Defend your groupings using your data to support you position.
5. From the introduction on the front, explain why permanent in your hair will not wash out.
Conductivity