Fats

Obtain real soap from vegetable oil!

Difficulty:
Danger:
Duration:
30 minutes
Fats

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
  • Remove protective gloves before lighting the candles.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

What kinds of vegetable oil can I use for this experiment?

Sunflower, coconut, peach, cottonseed, avocado, peanut, soybean, flaxseed, canola, hemp, grapeseed, safflower, milk thistle, olive, and sesame oils are all great options. Alternatively, you can try using lard, butter, or margarine. Corn and castor oils are not suitable for this experiment.

Step-by-step instructions

Vegetable oil is a good starting material when making soap.

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The next ingredient is an alkali, such as sodium hydroxide NaOH.

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The reaction between the oil and the alkali produces soap.

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Heat the mixture to speed up the reaction.

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Once the reaction is complete, you can make some soap bubbles.

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Disposal

Dispose of solid waste together with household garbage. Pour solutions down the sink. Wash with an excess of water.

Scientific description

Have you ever noticed how hard it is to wash fat or oil off your hands using just water? That's because water molecules are attracted to each other but not to fat. Water splashes around with minimal effect on fats. If only we could make fat cling to water, washing it off would become much easier... How about a molecule that is attracted to water at one end and attracted to fat at the other? And voila, we’ve uncovered the idea behind soap! But how is such a molecule actually made?

One obvious source for the "fat-loving" or, as scientists say, lipophilic part of the molecule is fat itself. The fat molecules in vegetable oil are made of glycerol  and three fatty acid  residues. Fatty acid "tails"  are indeed lipophilic, and the place where they bind to glycerol residue  would immediately look promising to a chemist. As it turns out, there's a trick called the "basic hydrolysis of esters", which boils down to adding a base, such as NaOH, to a compound with such a bond (also known as esters). Over the course of the reaction, the fatty acid residues break apart, exposing their "water-loving" (or hydrophilic) fragments . In the end, you get molecules with long lipophilic "tails"  and nice hydrophylic "heads" . And these molecules are exactly what we imagined when we thought of soap !