Lesson Notes By Weeks and Term v4 - SHS 1
SCIENCE AND MATERIALS IN NATURE
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SCIENCE AND MATERIALS IN NATURE
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Subject: General Science
Class: SHS 1
Term: 1st Term
Week: 10
Grade code: 2.1.1.LI.3
Strand code: 1
Sub-strand code: 1
Content standard code: 2.1.1.CS.1
Indicator code: 2.1.1.LI.3
Theme: EXPLORING MATERIALS
Subtheme: SCIENCE AND MATERIALS IN NATURE
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This lesson introduces two fundamental concepts in chemistry: concentration and pH. In our daily lives in Ghana, we constantly interact with solutions of different strengths – from the sweetness of our 'sobolo', the saltiness of seawater at our coast, to the strength of disinfectants we use at home. Understanding concentration helps us quantify "how much" of a substance is in a mixture. Similarly, the concept of pH helps us understand the acidic or basic nature of substances around us, which is crucial for farming (testing soil), health (indigestion), and even cooking. This lesson provides the scientific foundation to measure and describe these important properties of materials.
This lesson is divided into two main parts: understanding and calculating the concentration of solutions, and understanding and using the pH scale. Part A: Concentration of Solutions Basic Definitions Solution: A homogeneous mixture of two or more substances. This means the mixture is uniform throughout (e.g., when sugar dissolves in water, you can't see the individual sugar particles). Solute: The substance that is dissolved in a solution (e.g., the sugar). Solvent: The substance that does the dissolving (e.g., the water). The solvent is usually present in a larger amount. Concentration: A measure of the amount of solute dissolved in a specific volume of the solvent or solution. A solution with a lot of solute is concentrated. A solution with very little solute is dilute. Measuring Concentration There are two main ways we will measure concentration in this course:
a) Mass Concentration (g/dm³) This tells us the mass of solute (in grams) dissolved in one cubic decimetre (1 dm³) of the solution. The formula is: Mass Concentration (g/dm³) = Mass of solute (g) / Volume of solution (dm³) Important Conversion: Laboratory measurements are often in cubic centimetres (cm³). You MUST convert to dm³ before calculating. 1000 cm³ = 1 dm³ To convert cm³ to dm³, you divide by 1000.