Lesson Notes By Weeks and Term v4 - SHS 1
SCIENCE AND MATERIALS IN NATURE
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SCIENCE AND MATERIALS IN NATURE
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Subject: General Science
Class: SHS 1
Term: 2nd Term
Week: 4
Grade code: 3.1.1.LI.2
Strand code: 1
Sub-strand code: 1
Content standard code: 3.1.1.CS.1
Indicator code: 3.1.1.LI.2
Theme: EXPLORING MATERIALS
Subtheme: SCIENCE AND MATERIALS IN NATURE
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Carbon dioxide (CO₂) is a gas that is all around us. We breathe it out, and plants "breathe" it in. It's the fizz in your Fanta and Coca-Cola, and the gas that helps bread rise. In Ghana, it is fundamental to our agriculture (especially for crops like cocoa and maize through photosynthesis) and is used in industries from food processing to safety. Understanding how to prepare and use this important gas is a key scientific skill. This lesson will take us into the laboratory to see how we can make carbon dioxide and explore how its special properties make it so useful in our daily lives.
This topic is divided into three main parts: The laboratory preparation of CO₂, its properties, and its uses. Part A: Laboratory Preparation of Carbon Dioxide (CO₂) Gas
Principle: The most common and convenient method for preparing carbon dioxide in the laboratory is by the action of a dilute acid on a metal carbonate or bicarbonate. Metal Carbonate + Dilute Acid → Salt + Water + Carbon Dioxide
Reactants: Calcium Carbonate (CaCO₃): This is the chosen metal carbonate. It is readily available and affordable in various forms like marble chips, limestone, or even chalk. Eggshells are also primarily made of calcium carbonate. Dilute Hydrochloric Acid (HCl): This is the preferred acid for the reaction.
*Teacher's Note:* We do not use dilute Sulphuric Acid (H₂SO₄) with Calcium Carbonate. This is a very common examination question. The reason is that the reaction produces calcium sulphate (CaSO₄), which is insoluble in water. This insoluble salt forms a coating around the marble chips, preventing the acid from reaching the fresh calcium carbonate underneath, and the reaction quickly stops.