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: 6
Grade code: 1.1.1.LI.6
Strand code: 1
Sub-strand code: 1
Content standard code: 1.1.1.CS.1
Indicator code: 1.1.1.LI.6
Theme: PHYSICAL CHEMISTRY
Subtheme: MATTER AND ITS PROPERTIES
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This lesson takes us on a historical journey to understand the very building blocks of everything around us – the atom. From the waakye we eat to the air we breathe, all matter is made of atoms. But how do we know what an atom looks like inside? For a long time, scientists thought it was an unbreakable solid ball. This lesson explores two groundbreaking experiments that shattered that old idea and gave us our first glimpse into the subatomic world. Understanding these experiments helps us appreciate how scientific knowledge is built on evidence and is always evolving. It is the foundation for understanding chemical reactions, electricity, and even the technology in our mobile phones.
This lesson is divided into two main parts, focusing on the two key experiments that changed our understanding of the atom. Part A: The Discovery of the Electron – J.J. Thomson's Cathode Ray Experiment (1897)
Before Thomson, the atom was thought to be the smallest, indivisible particle of matter (Dalton's theory). Thomson's work proved that the atom itself has smaller parts.
The Experimental Setup:
The experiment used a Cathode Ray Tube (CRT). Imagine a sealed glass tube with almost all the air pumped out (a near-vacuum). At one end is a negative electrode called the cathode. At the other end is a positive electrode called the anode. A very high voltage (thousands of volts) is applied across these electrodes. The tube might have a fluorescent screen at the end which glows when struck by rays.