Plant oils matter: agricultural soap

What are the ingredients of products you use everyday like soap? Does it matter where they come from?

Soap made from soybeans? Sunflowers? Olives? Plant oils have different “fatty acids” that determine the characteristics of your soap—is it creamy? bubbly? hard? soft? It is the oil in plants that makes different kinds of soap. Try this easy, melt-and-pour soap recipe to get started. This activity is one of several from a 4H Agriscience Biotechnology Series.

# Agriculture in Soap

Use a recipe to make glycerine soap and describe it using an observation log. Learn about the history of soap and fatty acids.


Teacher background

Soap properties were discovered 3,000 years ago by the Romans. Animal fat had dripped down into the ashes of a cooking fire and that mixture dripped into a river where clothes were washed. People noticed that this fatty-ashy mixture cleaned clothes better than plain water. The science in this story is that the animal fat contained fatty acids and glycerine (triglycerides). The ashes contained a type of salt (a base known as alkali). When combined, the triglycerides and alkalis made soap. Today, the long names on the list of ingredients on a soap package, like “sodium stearate,” or “sodium palmitate,” are the names of the specific fatty acids present.

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Next gen science standards

Science and engineering practices

  • Asking questions (for science) and defining problems (for engineering)

Crosscutting concepts

  • Cause and effect

Disciplinary core ideas/content

  • ESS3A Natural resources
  • ETS2 Links among Engineering, technology, science and society
  • ETS2A Interdependence of science, engineering and technology
  • ETS2B Influence of engineering, technology and science on society and the natural world