Lesson Notes By Weeks and Term v4 - SHS 2
HEAT
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HEAT
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Subject: Physics
Class: SHS 2
Term: 1st Term
Week: 14
Grade code: 2.2.1.LI.2
Strand code: 2
Sub-strand code: 1
Content standard code: 2.2.1.CS.1
Indicator code: 2.2.1.LI.2
Theme: ENERGY
Subtheme: HEAT
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GHANA EDUCATION SERVICE (GES) SENIOR HIGH SCHOOL (SHS) LESSON NOTE Teacher's Name: [Your Name Here] Week Ending: [Date]
(40 minutes) A. Heat Capacity (C)
Imagine you have two different cooking pots, a small clay pot (*asanka*) and a large aluminium pot. To raise the temperature of both pots by just one degree, you would need different amounts of heat. The large pot would need more heat. Definition: Heat Capacity (C) of a body is the quantity of heat energy required to raise the temperature of the *entire body* by one Kelvin (1K) or one degree Celsius (1°C). Formula: `C = Q / Δθ` Where: `C` = Heat Capacity `Q` = Quantity of heat supplied (in Joules, J) `Δθ` = Change in temperature (in Kelvin, K, or degrees Celsius, °C) Unit: The SI unit for Heat Capacity is Joules per Kelvin (J/K) or Joules per degree Celsius (J/°C). B. Specific Heat Capacity (c)
Now, instead of the whole pot, let's consider the material itself. Is aluminium always easier to heat than clay, regardless of the size? To compare materials fairly, we need to consider the same mass of each. This leads us to *specific* heat capacity. Definition: Specific Heat Capacity (c) of a substance is the quantity of heat energy required to raise the temperature of a *unit mass (1 kg)* of that substance by one Kelvin (1K) or one degree Celsius (1°C). This is a characteristic property of a substance. Water has a very high specific heat capacity, while metals have low ones. Formula: `c = Q / (m * Δθ)` Rearranging this gives us the most important formula for this topic: `Q = mcΔθ`
Where: `Q` = Quantity of heat supplied or lost (in Joules, J) `m` = mass of the substance (in kilograms, kg) `c` = specific heat capacity of the substance (in J/kgK or J/kg°C) `Δθ` = change in temperature (θ_final - θ_initial) in K or °C. *(Note: A change of 1°C is the same as a change of 1K, so the units are interchangeable for Δθ)*. Unit: The SI unit for Specific Heat Capacity is Joules per kilogram per Kelvin (J/kgK) or Joules per kilogram per degree Celsius (J/kg°C). *Specific Heat Capacity of Water ≈ 4200 J/kgK* *Specific Heat Capacity of Copper ≈ 400 J/kgK* C. Relationship between C and c