• Question: why does oil seperate when you put soap in it

    Asked by abiola to Angela, Karen, Shane on 21 Nov 2013.
    • Photo: Karen McCarthy

      Karen McCarthy answered on 21 Nov 2013:

      This is another great question abiola, and crucial to the process of soapmaking! Well soap is made of different molecules – and if imagine a molecule to be like a ruler, well then one end of the ruler loves water (hydrophilic) and the opposite end of the ruler hates water (hydrophobic).

      The water-hating ends attract all the oil, whilst the water-loving ends attract the water = causing droplets of oil in the water. This process is exactly how soap cleans your hands – it attracts all the dirt, oil and grease, and transfers them into the water!


    • Photo: Angela Stevenson

      Angela Stevenson answered on 21 Nov 2013:

      I loved experiments with water and oil when I was younger! Great question! Some things just don’t get along well with each other, oil and water are a perfect example. You can mix them together and shake as hard as you d like but they just don’t seem to want to mix. We can blame their chemical properties for that 😉 Water molecules are strongly attracted to each other and this is the same for oil, and because they are more attracted to their own molecules they just don’t mix together. They separate and the oil floats above the water because it has a lower density. In order to get water to mix with oil you need to break the strong bonds that they form with their own species. That’s why adding dish washing liquid helps! Soap is attracted to both water and oil helping them all join together, which is why it’s so effective at cleaning our greasy, oily dishes!