Lab: IONIC & COVALENT COMPOUNDS
Introduction:
The phrase CHEMICAL BOND refers to the strong electrical force of attraction between atoms or ions in a substance. There are
4 different types of bonding (Ionic, Polar Covalent, Non Polar Covalent, and Metallic). This lab will focus on Ionic and Covalent
bonding.
Ionic bonding is the complete transfer of valence electron(s) between atoms. It is a type of chemical bond that
generates 2 oppositely charged ions. In ionic bonds, the metal loses electrons to become a positively charged cation (ex: Ca2+
ion), and the non-metal gains those electrons to become a negatively charged anion (ex: Cl1- ion). Ionic bonds require an
electron donor, the metal, and an electron accepter, the nonmetal.
Covalent bonding is the sharing of electrons between atoms. This type of bonding occurs between two of the same
element or elements close to each other in the periodic table. This bonding usually occurs between nonmetals (example
carbon dioxide, CO2 or chlorine gas, Cl2); however, it can rarely also be observed between nonmetals and metals as well.
In this experiment, you will observe several properties of ionic and covalent compounds and attempt to recognize
patterns among the properties.
Purpose / objective:
1. Compare the properties of several common Ionic and Covalent substances.
2. Interpret the property data to classify each Unknown substance (A, B, C, D) as ionic or covalent.
Materials:
Safety glasses
Test tubes
DI H2O (distilled water)
C6H4(OH)COOH (salicylic acid)
Bunsen burner
Rubber Stoppers
ETOH (ethyl alcohol)
NaCO3 (sodium carbonate)
Conductivity tester
Test tube rack
C6H12O6 (sucrose)
C6H5COOH (benzoic acid)
Beakers
NaCl (table salt)
Procedures:
Part I- Teacher demonstration:
1. Your teacher will heat a small amount of each substance in a test tube over a Bunsen burner.
2. Record the time required for the material to melt completely.
3. If the substance has not melted after 90 seconds, record it as non-melting.
Part II – Each Lab Group
Process 1
1. Label and keep track of 4 test tubes with each of the four substances.
2. One at a time, put a small amount of each substance(the size of a small pea) in one of the test tubes. ONE SUBSTANCE
PER TEST TUBE. DO NOT CONTAMINATE THE MICRO-SPATULAS! Be sure to return each micro-spatula in their correct
sample container after obtaining each sample to avoid contamination!
3. Fill each test tube to about 1/4-full with ETOH. Place a rubber stopper in the test tube and shake for one minute.
4. Record whether or not it dissolves in the ethanol.
5. Clean out your test tubes with tap water, and empty the substance down the sink.
6. Rinse the excess tap water out with DI water.
Process 2
1.
2.
3.
4.
Repeat the process above with the same 4 substances.
Fill each test tube to about 1/4-full with deionized H2O. Place a rubber stopper in the test tube and shake for one minute.
Record whether or not it dissolves in water.
Clean your test tubes with tap water, and return to the test tube rack to dry.
Process 3
1. Proceed to the teacher’s conductivity testing station.
2. One at a time, test each solution to determine or not electricity is conducted by placing the anode and cathode conductors
inside the beakers of solution. Completely submerge the anode and cathode so the solution is completely covering them.
Record your observations. DO NOT TOUCH the tester or the solution while the cord is plugged in.
3. Between each conductivity test, dip the anode and cathode conductors in deionized H2O in order to CLEAN THE
CONDUCTORS from contamination. DO THIS BEFORE EACH TEST!
4. Repeat the conductivity test for each solution and record your observations.
Name _______________________________________
Date____________________ Hour _________
QUESTIONS:
1. Why do you use deionized water instead of tap water during the conductivity tests?
2. From the lab data, how do you know if a substance is Ionic?
3. Which substances from the laboratory data conduct electricity better? WHY!
4. Which group of substances from the laboratory data has the higher melting point? What does that tell you about the
bonds within the compound?
5. Use the concepts of ionic and covalent bonding to explain why ionic substances are able to conduct electricity better
than covalent ones.
6. Is salt an ionic or covalent compound? Justify your answer.
7. Is benzoic acid an ionic or covalent compound? Justify your answer.
8. A substance does not melt under flame but it does conduct an electrical current. Predict whether this substance is
Ionic or Covalent?