In the cleansing action of soap, how do the soap molecules interact with greasy stains on fabric immersed in water?

Answer and explanation

Correct answer: B. Hydrophobic tails dissolve in grease while hydrophilic heads interact with water

  1. Step 1: Analyze soap molecule structure: a soap molecule has a non-polar hydrocarbon tail (hydrophobic) and an ionic carboxylate head (, hydrophilic).
  2. Step 2: The hydrophobic tails penetrate and dissolve into the non-polar grease droplet, while the ionic heads project outward into polar water molecules. Agitation breaks grease into spherical micelles suspended in water.
Answer
Hydrophobic tails dissolve in grease while hydrophilic heads interact with water.
Why not the others: 'Hydrophilic heads dissolve in grease while hydrophobic tails dissolve in water' reverses the solubilities of polar and non-polar parts; 'Both hydrophobic tails and hydrophilic heads repel the grease stain completely' would prevent any cleansing action; 'Soap molecules react chemically to oxidize grease into gaseous carbon dioxide' confuses emulsification with combustion.

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