Lesson Notes By Weeks and Term v4 - SHS 3

Lesson Video

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Performance objectives

• Explain why chemicals should be stored by compatibility, not alphabetically.
• Identify pairs of chemicals that are dangerous to store together.
• Understand how to respond to a small fire using safety equipment.
• Recognize the importance of lab safety in our communities.

Lesson summary

This lesson focuses on a critical aspect of laboratory safety: the proper storage of chemicals. While it might seem logical to arrange chemicals on a shelf alphabetically, like books in a library, this practice is extremely dangerous and can lead to fires, explosions, or the release of toxic gases. In Ghana, where we use chemicals in schools, hospitals, small-scale industries (like soap making and tie-dye), and on farms, understanding safe storage is a vital life skill that protects ourselves, our community, and our environment. This lesson will explore the principle of chemical compatibility and explain why we must group chemicals by their reactive properties, not their names.

Lesson notes

A. The Fallacy of Alphabetical Storage

Imagine arranging people at a large family gathering. You could arrange them alphabetically by their first name. However, if two cousins, Kwaku and Kwame, have a long-standing quarrel, seating them next to each other just because their names are similar would be a recipe for disaster. The same logic applies to chemicals.

Alphabetical storage is dangerous because it ignores the reactivity of substances. It can place highly reactive and incompatible chemicals right next to each other on the shelf. Example: Acetic Acid would be stored next to Acetaldehyde. Acetic acid is a corrosive acid, while acetaldehyde is a flammable liquid that can polymerize violently. A simple spill could cause a fire. Nitric Acid might be stored next to Naphthalene. Nitric acid is a powerful oxidizing agent, and naphthalene is a flammable solid. If their containers leak and they mix, a violent fire or explosion could occur.

The primary rule of chemical storage is: Store like with like, and separate the incompatibles. B. Chemical Compatibility: The Foundation of Safe Storage

Evaluation guide

• Explain why chemicals should be stored by compatibility and not alphabetically in the
• laboratory.
• Exploratory Learning:
• Visit the school chemical store or Chemistry laboratory to observe how chemicals are stored.