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: 12
Grade code: 1.1.1.LI.4
Strand code: 1
Sub-strand code: 1
Content standard code: 1.1.1.CS.2
Indicator code: 1.1.1.LI.4
Theme: PHYSICAL CHEMISTRY
Subtheme: MATTER AND ITS PROPERTIES
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Welcome, future scientists and engineers! Today, we are revisiting a fundamental concept in Chemistry that acts as a bridge between the microscopic world of atoms and molecules and the macroscopic world we see and measure in the lab. This is the concept of the 'mole'. Why does this matter in your life here in Ghana? Imagine you are a pharmacist determining the correct dosage for a medicine, a food scientist ensuring a product has the right amount of nutrients, or an agricultural officer advising a farmer on how much fertilizer to apply.
This lesson focuses on the relationships between four key quantities: Amount of substance (n), measured in moles (mol). Mass (m), measured in grams (g). Number of particles (N), which is a count of atoms, molecules, or formula units. Volume of gas (V), measured in cubic decimetres (dm³).
The mole is the central concept that connects all of these. Concept 1: The Mole and Molar Mass (Connecting Moles and Mass) The Mole (n): The mole is the SI unit for the amount of a substance. One mole contains exactly 6.02 x 10²³ elementary entities (particles). This huge number is called Avogadro's Constant (L or Nₐ). Think of it like a "chemist's dozen". We say 1 dozen eggs = 12 eggs; a chemist says 1 mole of carbon atoms = 6.02 x 10²³ carbon atoms. Molar Mass (M): This is the mass, in grams, of one mole of a substance. Its unit is grams per mole (g/mol). For an element, the molar mass is numerically equal to its relative atomic mass on the periodic table. Example: Molar mass of Carbon (C) = 12.0 g/mol. Example: Molar mass of Sodium (Na) = 23.0 g/mol. For a compound, the molar mass is the sum of the molar masses of all the atoms in its formula. Example: Molar Mass of Water (H₂O) = (2 × 1.0) + 16.0 = 18.0 g/mol. Example: Molar Mass of Sodium Chloride (NaCl) = 23.0 + 35.5 = 58.5 g/mol.
The relationship is given by the formula: `Amount (n) = Mass (m) / Molar Mass (M)`
This can be rearranged to find the mass: `Mass (m) = Amount (n) × Molar Mass (M)`