The following statement describes the assessable content for this sub-section, as described in the SQA arrangement documents.
|Cleaning with water alone has little effect when stains consist of non-polar substances, such as grease and sweat. Soap ions have a long non-polar tail, readily soluble in non-polar compounds (hydrophobic), and an ionic carboxylate head which is water soluble (hydrophilic). During cleaning, the hydrophobic tails dissolve in a droplet of oil or grease, whilst the hydrophilic heads face out into the surrounding water resulting in ball-like structure. The non-polar substances, such as oil and grease, are held inside the ball and suspended in water.|
This animation studies the structure of soap molecules and describes how the presence of the polar, hydrophilic head and the non-polar, hydrophobic tail allow cleaning to take place.