Covalent and Ionic Properties
Purpose: In this lab you will examine the properties of volatility, melting point, and
solubility in order to differentiate between ionic compounds and covalent molecules.
Introduction: In ionic compounds, the force of attraction is between oppositely charged
ions. This attraction is called an ionic bond, and it occurs when atoms trade electrons. In
covalent molecules, the atoms are held together because electrons are shared between
atoms. These different forces account for the many properties of ionic and covalent
compounds such as solubility, melting point, and volatility.
Melting Point- This is the temperature at which a solid turns into a liquid.
Volatility – This describes how easily a substance is evaporated. The more
volatile, the more you smell it, which indicates a greater amount of the substance is
evaporating.
Solubility – This describes how likely a substance is to dissolve in water. When a
substance dissolves, water molecules surround individual ions or molecules.
Procedure:
1. Volatility Test– Carefully smell each compound. If you can detect an odor,
assume that the compound has a high volatility. Record as high or low volatility.
2. Melting Point – Place a small amount of substance in the tube meant to be placed
inside the melting point apparatus. Watch as the substance melts. Record the
temperature at which melting occurs.
3. Solubility in Water – Put a pea-sized amount of substance into 4 mL of water in a
test tube. Stir to combine. Record high solubility (dissolves) or low solubility
(does not dissolve).
Conclusion Questions:
1. Based on your results, which of the substances were ionic?
2. Which were covalent?
3. What kinds of elements are in the formulas for the ionic compounds?
4. What kinds of elements are in the formulas for the covalent compounds?
5. List the physical properties that indicate ionic bonding exists in a compound.
6. List the physical properties that indicate covalent bonding exists in a compound.