Investigation of a Type, Structure, and Factors Determining Stability of Emulsions: Laboratory Scenario for K9–K12 Students

Abstract

Emulsions are part of our everyday lives, from delicious mayonnaise, milk, butter, and vinaigrette sauce to cosmetics, such as creams, body lotions, cleansing milks, and hair conditioners. Additionally, emulsions are present in medicines, paints, and other products. This wide range of applications provides an interesting and engaging context for introducing dispersion systems during chemistry lessons. When discussing the properties of emulsions, we have an unusual opportunity in school chemistry: we can observe the structure of a substance under an optical microscope and directly link its microscopic structure to its macroscopic properties and its symbolic description. This article describes a laboratory activity that investigates how the composition, emulsifier type, and preparation method influence the type and stability of the resulting emulsions. Moreover, students prepare an emulsion, a functional cosmetic: a moisturizing cream. The activity was tested with 328 upper secondary school students (K11), and its pedagogical effectiveness has been confirmed.