Lesson Notes By Weeks and Term v4 - SHS 3
HEAT
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HEAT
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Subject: Physics
Class: SHS 3
Term: 1st Term
Week: 17
Grade code: 3.2.1.LI.3
Strand code: 2
Sub-strand code: 1
Content standard code: 3.2.1.CS.1
Indicator code: 3.2.1.LI.3
Theme: ENERGY
Subtheme: HEAT
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Welcome, students! Today, we are exploring a very practical aspect of heat energy: Thermal Expansion. Have you ever wondered why there are small gaps in railway lines, like the ones on the Accra-Tema line? Or why electricians from ECG leave overhead power cables sagging instead of pulling them tight? The answer lies in how materials, especially metals, behave when they get hot. In Ghana's hot climate, understanding this is crucial for engineers, mechanics, and even in our own homes. We will learn about a specific property called linear expansivity and use it to predict and compare how much different metals expand.
A. What is Thermal Expansion?
When most substances are heated, their particles (atoms and molecules) gain kinetic energy and vibrate more vigorously. This increased vibration causes the particles to move further apart, leading to an increase in the size of the substance. This phenomenon is called thermal expansion. Solids expand in length, area, and volume. Liquids and gases primarily expand in volume.
Today, we will focus on the expansion in length, which is known as Linear Expansion. B. Linear Expansion and the Coefficient of Linear Expansion (α)
Linear Expansion is the increase in the length of a solid when its temperature is increased.