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11EOT TERM 2(C-PLAN)
Al Maha School Chemistry Grade 11 - EOT Term 2
Teacher: Ms. Sarah Ramadan
Module 21: Solutions
Topics Covered:
Surface area calculations
Factors affecting rate of dissolving
Solubility rankings at 20°C
Solubility curve analysis
Comparison of various solutions: unsaturated, saturated, supersaturated
Solubility of gases
Differences between dissociation and ionization
Effects of adding antifreeze to water
Factors affecting solute particles
Comparison of ethanol and sodium stearate
Soap functionality in cleaning dirt
Polarity and vitamin solubility
Lesson 1: How Solutions Form
Key Definitions
Solution: A homogeneous mixture, having the same composition throughout.
Solute: The substance being dissolved (e.g., sugar, salt).
Solvent: The substance in which the solute is dissolved (e.g., water).
Types of Solutions
Liquid Solutions: Solute can be a solid, liquid, or gas dissolved in liquid (e.g., saltwater, carbonated drinks).
Nonliquid Solutions: Gaseous solutions (e.g., air) and solid solutions (e.g., alloys like bronze).
Example of Solution Formation
In sugar-water, sugar is the solute and water is the solvent. Gases like oxygen dissolve in water to form gas-liquid solutions.
Properties of Solutions
Solutions can exist in different states: Solid (alloys), Liquid (sugar in water), and Gas (air).
Solubility: The maximum amount of solute that can dissolve in a solvent at a specific temperature.
Factors Affecting Rate of Dissolving
Stirring: Increases interaction of solute and solvent, speeding up dissolving.
Surface Area: Greater surface area of solute speeds up dissolving (e.g., powdered sugar dissolves faster than sugar crystals).
Temperature: Increasing temperature of the solvent enhances the dissolving process.
Types of Solutions by Concentration
Comparisons:
Unsaturated Solution: Can still dissolve more solute.
Saturated Solution: Contains maximum solute possible at a given temperature.
Supersaturated Solution: Holds more solute than a saturated solution at the same temperature and is unstable.
Characteristics:
Seed crystals added to supersaturated solutions can cause solute to precipitate out.
Solubility of Gases
Effect of Pressure: Increasing pressure increases gas solubility in liquids (e.g., carbonated beverages).
Effect of Temperature: Cooling liquids increases gas solubility; warm liquids release dissolved gases (e.g., opening a warm soda).
Dissociation vs. Ionization
Dissociation: Ionic compounds breaking apart into ions when dissolved in solution (e.g., salt in water).
Ionization: Molecular compounds forming ions in solution (e.g., HCl in water forming H+ and Cl-).
Effects of Solute Particles
Solute particles affect physical properties of solvents (e.g., freezing and boiling points).
Antifreeze: Lowers freezing point and raises boiling point of solutions, useful in car radiators.
Comparison of Ethanol and Sodium Stearate
Structure:
Ethanol: Contains a polar -OH group and a nonpolar chain;
Sodium Stearate: Polar ionic end and long nonpolar hydrocarbon tail.
Functionality:
Effective at dissolving both polar and nonpolar substances, crucial in soap-making.
Soap Cleansing Mechanism
Soap has both polar and nonpolar ends; the polar end dissolves in water while the nonpolar end interacts with oil/dirt.
Soaps are salts of fatty acids that facilitate the removal of oily dirt by emulsification.
Vitamins and Polarity
Fat-soluble vs. Water-soluble Vitamins
Fat-soluble Vitamins: (e.g., A) dissolve in fat and can accumulate in tissues.
Water-soluble Vitamins: (e.g., B, C) dissolve in water and are excreted in urine; not stored.
Summary of Acid-Base Concepts (Module 22)
Acid Definition
Acids produce hydrogen ions (H+) in solution and are sour, corrosive, and react with indicators (e.g., litmus paper).
Indicators change color in the presence of acids/bases, e.g., blue to red in acid.
Common Bases
Bases produce hydroxide ions (OH-) when dissolved and can neutralize acids.
Key Reactions & Neutralization
Neutralization: Acid + Base → Salt + Water
Summary
A comprehensive understanding of solutions, their formation, the impact of various factors on solubility, the concepts of acids and bases, and their applications in various contexts.
