Question

Which of the following occurs when a greasy plate is placed in soapy water and scrubbed?

• A. The soap froths but does not actually bond with the grease.
• B. The hydrophobic tail of the soap bands to water.
• C. The hydrophobic tail of the soap bonds to grease.
• D. The hydrophilic head of the soap bonds to grease.

Answer 1

The correct option is C The hydrophobic tail of the soap bonds to grease.

When a greasy plate is placed in soapy water and scrubbed then the hydrophobic tail of the soap bonds to grease. The non-polar end adsorbs the oil or other hydrophobic dirt. The ionic end is highly soluble in water. This allows for an emulsion to be formed. The structure of the emulsion is such that grease is surrounded by soap molecules with the ionic part of the molecules toward the outside where water will react with the ionic end (by hydrogen bonding) and keep the grease oil in the solution.