Grade IX
The topic of mixtures is studied across different grades with and increasing complexity. While the introductory levels involve simple separation techniques, it gradually gains in complexity, dealing with advanced techniques like chromatography. Colloids is one group of mixtures that is widely used in the food and cosmetic industry. It is, therefore, important that the students deeply explore this concept.
In this module, the activities have been structured to provide the students a hands-on experience to enable them to arrive at a proper understanding about mixtures and their uses. The students will learn that the components of a mixture are separated based on their physical as well as chemical properties. They will explore the optical property of colloids, suspensions, and true solutions as well as practice the preparation of a few commonly used colloids.
Separation of mixtures: In this activity, the students will understand the basis of separation of colloids by separating the substances of a mixture of common salt, camphor, sand, and iron filings.
Tyndall effect: This demonstration will help the students distinguish between colloids, true solutions, and suspensions based on their optical properties.
Understanding colloids: The students will identify the difference between an oil-based and a water-based colloid by preparing different colloids and observing them under a microscope.
Making colloids: In this activity, the students will make toothpaste and mayonnaise by themselves. Through this, they will be able to understand the applications of colloids in their daily lives.
Assessment: A quick and simple assessment tool is available at the end of this module to check the students’ understanding of the topic.
Image credits: https://commons.wikimedia.org/wiki/File:Fe-S_mixture_02.jpg
Ciênc. Tecnol. Aliment., Campinas, 30(2): 477-482, abr.-jun. 2010
Term: Term 1
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