Chemical Bonds Lab
Objective:
To identify the 4 properties of ionic and covalent bonds: Relative melting points, ethanol
solubility, water solubility and conductivity.
Apparatus:
Tin lid, Iron ring and stand, several 4 mL test tubes, glass stirring rod, conductivity tester.
Materials:
DI water with pipette
Candle
Ethanol (C2H5OH) – denatured (made poisonous), flammable
Sucrose (C12H24O11) - sugar
Sodium chloride (NaCl) – table salt
Para-dichlorobenzene (Moth Balls) – poisonous and an irritant
Potassium iodide (KI)
Camphor (active ingredient in Vick’s vapor rub) – flammable
Potassium bromide (KBr) – poisonous
Introduction: Chemical compounds are combinations of atoms held together by
chemical bonds. This lab focuses on ionic and covalent bonds. An ionic bond occurs when one
or more electrons from one atom or group of atoms are transferred to another atom. Positive and
negative ions are created. These ions are strongly attracted to each other. Covalent bonds
involve the sharing of electron pairs by bonded atoms.
The physical properties of a substance such as melting point, solubility in ethanol and water, and
conductivity tell us a lot about the bond in the compound. In this lab you will determine the
properties of several compounds. Compiling data will enable you to classify these compounds as
either ionic or covalently bonded.
Procedure1. Record a description of each substance in the data table.
2. Using an iron ring and ring stand, fix the ring above the tip of a candle flame.
3. Place a small sample (a few crystals)of KBr, camphor, p-dichlorbenzene, KI, NaCl, and sucrose
in separate location in the aluminum pan. Keep them as far apart from each other as possible.
4. Place the aluminum pan and compounds on the ring above the low flame. Record the order of
melting in the data table. After approximately 2 minutes if the substance has not melted, record
N/C for no change for that substance.
5. Clean several 4 mL test tubes. Use detergent, rinse with tap water, rinse with DI water and shake
dry. Label the test tube rack. You will need 6 test tubes.
6. Place a very small amount of each substance in a separate test tube.
7. Add 1 cm of ethanol in each test tube.
8. Stir. Be sure to rinse the stirring rod between stirring of samples.
9. Record the solubility (Does it dissolve? Yes or no) for each substance in the ethanol.
10. Repeat steps 5-9 but this time use DI water instead of ethanol.
11. Take the conductivity tester and submerge the electrodes in the solutions. If the bulb of the
conductivity tester glows, the solution conducts electricity. Record the results. To avoid
contamination, a beaker of DI water should be used to rinse the electrodes between tests.
12. Clean the test tubes, and other apparatus and put things back in their proper place.
Name_________________________________________Pd______
DATA TABLE: (12 pts)
Compound
#
Potassium
bromide
Camphor
1
p-dichloro
benzene
Potassium
iodide
Sodium
chloride
Sucrose
3
Description
a.
b.
Melting Ethanol
order
solubility
c.
Water
solubility
d.
Solution
Conduc
-tivity
Ionic or
Covalent
2
4
5
6
Questions:
1. Conclude four general properties of ionic compounds tested in this lab. Circle the underlined word(s) that
make the statement true. ( 4 pts)
a. Ionics have high or low melting points
b. Ionics Do or do not dissolve in ethanol
c. Ionic Do or do not dissolve in water.
d. Ionics are Conductive or Non- conductive
2. Conclude four general properties of the covalent compounds tested in this lab. ( 4 pts)
a. Covalents have high or low melting points
b. Covalents Do or do not dissolve in ethanol
c. Covalents Do or do not dissolve in water.
d. Covalents are Conductive or Non- conductive
3. List the ionic compounds studied in this lab. ( 3 pts)
1.)
2.)
3.)
4. List the covalent compounds studied in this lab. ( 3 pts)
1.)
2.)
3.)
5. Which one substance dissolves in both ethanol and water? ( 1 pt)