Surfactants: Helping Molecules Get Along
Surfactants are engineered for specific purposes and are commonly used in paints, dyes, inks and cleaning products, as well as an uncountable number and variation of consumer products.Copyright USDA; Job Corps; OSHA, US Dept. of Labor; Texas General Land Office http://www.ars.usda.gov/is/pr/1998/980303.htm?pf=1 http://columbiabasin.jobcorps.gov/vocations.aspx http://www.osha.gov/dcsp/products/etools/printing/flexography/flexography_index.html http://www.glo.texas.gov/what-we-do/caring-for-the-coast/oil-spills/response/oiled-wildlife.html
Students learn about the basics of molecules and how they interact with each other. They learn about the idea of polar and non-polar molecules and how they act with other fluids and surfaces. Students acquire a conceptual understanding of surfactant molecules and how they work on a molecular level. They also learn of the importance of surfactants, such as soaps, and their use in everyday life. Through associated activities, students explore how surfactant molecules are able to bring together two substances that typically do not mix, such as oil and water. This lesson and its associated activities are easily scalable for grades 3-12.
Engineers use surfactants in many aspects of material development and industrial manufacturing. For example, surfactants are commonly used in paints and dyes to improve adhesive properties and ensure even spreading on building surfaces and consumer packaging. The concepts of molecular polarity and surface tension are widely researched and applied in many aspects of engineering science, including their end use in paints, dyes, cosmetics, lubricants, pharmaceuticals, and textile production. Surfactants can be found in almost every consumer product — from a Twinkie wrapper to the ink in a pen.
After this lesson, students should be able to:
- Define polarity and identify the differences between polar and non-polar molecules.
- Identify the impact of polarity on interactions between molecules (for example, oil and water, water on a surface).
- Describe surface tension and how it affects the shape of water.
- Calculate the surface area of a sphere and a cube and determine that a sphere has the least surface area for a given volume.
- Understand how surfactants act to reduce surface tension between polar and non-polar molecules and facilitate their mixing.