Lesson Notes By Weeks and Term v4 - SHS 3
MATTER AND ITS PROPERTIES
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MATTER AND ITS PROPERTIES
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Subject: Chemistry
Class: SHS 3
Term: 1st Term
Week: 3
Grade code: 1.1.1.LI.5
Strand code: 1
Sub-strand code: 1
Content standard code: 1.1.1.CS.1
Indicator code: 1.1.1.LI.5
Theme: PHYSICAL CHEMISTRY
Subtheme: MATTER AND ITS PROPERTIES
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This lesson explores the very foundation of chemistry: the atom. We will begin by looking at one of the first modern scientific theories about atoms, proposed by John Dalton. Understanding this helps us appreciate how scientific knowledge evolves. Just as important as knowing what matter is, is knowing how to handle it safely. Therefore, we will also learn to recognise and understand laboratory hazard symbols. This knowledge is not just for the lab; it keeps us safe when using products like insecticides on the farm, bleach at home, or even when working in future careers in health, engineering, or industry right here in Ghana.
This lesson is divided into two main parts: the theory of the atom and the practical safety of handling chemical matter. Part A: Dalton's Atomic Theory (The Foundation)
John Dalton, an English scientist, proposed his atomic theory around 1803. It was a major step forward in chemistry, as it provided a framework for explaining chemical laws like the Law of Conservation of Mass and the Law of Constant Composition.
The Main Postulates of Dalton's Atomic Theory: All matter is composed of extremely small, indivisible particles called atoms. *Explanation:* Dalton imagined atoms as solid, tiny spheres that could not be broken down into anything smaller. Think of them like the smallest possible 'kenkey' ball that you cannot divide any further. Atoms of a given element are identical in mass, size, and other properties. *Explanation:* This means that every single atom of gold is exactly the same as every other atom of gold. An atom of oxygen from the air in Accra is identical to an atom of oxygen from a tree in Kumasi. Atoms of different elements differ in mass, size, and other properties. *Explanation:* An atom of carbon is fundamentally different from an atom of nitrogen. They have different weights and behaviours. Atoms combine in simple, whole-number ratios to form chemical compounds. *Explanation:* You can have H₂O (water), but you cannot have H₂.₅O. Atoms combine in fixed, predictable ratios, like 2 hydrogens to 1 oxygen. This explains why a compound like water always has the same composition. In chemical reactions, atoms are combined, separated, or rearranged. Atoms cannot be created, destroyed, or changed into atoms of another element. *Explanation:* This is essentially the Law of Conservation of Mass at the atomic level. When you burn wood, the carbon atoms from the wood combine with oxygen atoms from the air to form carbon dioxide. The atoms are just rearranged into new partnerships; none are lost or gained.
Weaknesses and Limitations of Dalton's Theory