Purpose
An experiment will be conducted to investigate the properties of both ionic and covalent compounds. On examining the characteristics and behavior of the substances that have been presented in the samples A, B and C, a thorough analysis can be carried out, correlating their properties to their chemical nature, either ionic or covalent
Procedure
Part A
Heat the samples on a hotplate and observe if the melting is within 3 minutes.
On the data table, record your observations.
Part B
Scoop each of the substances on a wax paper and observe them.
Record on the data table the appearances of each substance
Part C
Add about 5ml of water in each test tube.
Add a scoop of each of the substances into each of the test tubes.
Add a stopper to each of the test tubes and briefly shake.
Record your observations on the data table if the substances dissolve or not in water.
Part D
On each well add the 3 substances
Add water to each well and mix.
Dip the electrodes of a conductivity tester to test the conductivity of each of the solutions.
Record your observations on the data table.
Observations
| Sample A | Sample B | Sample C | |
| Melting Point | Over 3 minutes | Under 3 minutes | Under 3 minutes |
| Physical Appearance | White colorCrystalline consistencyFine granules | White colorGranular consistencyCoarse granules | White colorPowdery consistencyFine granules |
| Solubility in Water | Completely dissolves in water | Forms white precipitate when mixed with water | Completely dissolves in water |
| Conductivity | Conducts | Does not conduct | Does not conduct |
| Ionic or Covalent | Ionic | Covalent | Covalent |
Results
Ionic or covalent nature
The sample A is seen to be ionic due to its ability to conduct electricity and its having the ability to dissolve in water. Both characteristics indicate that they are ionic compounds which dissociate into ions when in solution form.
Sample B and C are covalent due to their inability to conduct electricity. This clearly indicates that they do not dissociate into ions when in solution form. This is a characteristic of covalent compounds.
Solubility patterns
Sample A is seen to completely dissolve in water. In general, ionic compounds are highly soluble in water which is consistent with the behavior of the substance.
Sample B, when dissolved in water is seen to form a precipitate. This suggests that it is partially soluble in water. The sample may be a polar covalent compound with limited solubility.
Sample C completely dissolves indicating it to be a polar covalent compound with high solubility in water.
Melting point
The melting point of the Sample A is higher than three minutes, which indicates that it is an ionic compound Cheng S et al (2020). This is because they are characterized by strong electrostatic forces in their lattice structure. The samples B and C have lower melting points. This is because covalent substances have weak intermolecular forces that can easily be broken down.
Electrical conductivity
The mobile ions contained in sample A when in aqueous or molten state give it the ability to conduct electricity Zhang S et al (2022).
Covalent compounds do not have free ions like ionic compounds in aqueous or molten state. Hence, they are not able to conduct electricity.
Predictions
Solubility of Sodium iodide in water
Sodium iodide (Nal) is an ionic compound, like sodium chloride. We expect it to be highly soluble when mixed with water because they the ion-dipole interaction between the sodium and iodide ions and the polar molecules of water.
Melting point of sodium iodide
The melting point of sodium iodide is high due to the strong ionic bonds in its crystal lattice that take a long time and energy to break.
Electrical conductivity of a glucose solution
Glucose does not conduct electricity as it is a covalent compound. There is no dissociation into ions like ionic compounds when mixed with water. This is why it does not conduct electricity.
Conclusion
This thorough analysis demonstrates the stark differences between ionic and covalent compounds. We can clearly see that ionic compounds have high melting points, conduct electricity in molten or aqueous state and readily dissolve in water. On the other hand, covalent compounds have no ability to conduct electricity when mixed with water and have lower melting points. The have variable solubility depending on the polarity of their molecules.
References
An D, Cheng S, Xi S, Zhang Z, Duan X, Ren Y, Li J, Sun Z, Liu Y, Wong CP. Flexible thermal interfacial materials with covalent bond connections for improving high thermal conductivity. Chemical Engineering Journal. 2020 Mar 1;383:123151.
Wu R, Zhang S, Song Q, Tan Y. Synthesis and solution properties of hydrophobically associating water-soluble copolymer with dynamic covalent bond. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2022 Sep 5;648:129260.
