Chapter 15.1, Problem 4RQ

Interpretation Introduction

Interpretation: Grease doesn’t dissolve in water easily by itself has to be explained.

Concept introduction: Solution is mixture in which all components are uniformly distributed. Any solution has 2 substances: solute and solvent. For formation of solution compatibility between solute and solvent is required. Example is salt solution and sugar solution.

Answer to Problem 4RQ

Since like dissolves like, therefore, grease which is a non polar molecule doesn’t dissolve itself in water as water has polar characteristics.

Explanation of Solution

Polar solvents like water can only dissolve polar solutes like $\text{NaCl}$ and ${\text{CH}}_3\text{OH}$ . In case of water molecules, hydrogen bonding is prevalent force between molecules to hold them together. For dissolving salt that is $\text{NaCl}$ in water, this hydrogen bond between water molecules has to be overcome.

So basically water dissolves polar solvents because it results into solute-solvent interactions similar to those present in pure water.

Similarly non polar solvents dissolve non polar solutes. Grease is a non polar molecule whereas water is polar in nature, so water doesn’t dissolve it. Some dry cleaning solvent which is non polar in nature is required to dissolve grease stain in it.

Conclusion

Since like dissolves like, therefore, grease which is a non polar molecule doesn’t dissolve itself in water as water has polar characteristics.