Lesson Notes By Weeks and Term v3 - Primary 5
Acids and Bases
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Acids and Bases
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Subject: Basic Science
Class: Primary 5
Term: 3rd Term
Week: 11
Theme: Living And Non-Living Things
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Watch on YouTubeSee Facebook postgive examples of acids and bases list some physical properties of acids and bases state types of acids and bases list some uses of acids and bases distinguish between acids and bases name local materials used in making soap identify the active in gredients in the local material used in making soap make soap from local materials state the uses of soap
(can be done with a stick or mixer) until the mixture thickens and reaches "trace" – a point where the mixture leaves a visible mark when drizzled on its surface, like thin pudding.
6. Additives (Optional): At trace, any colourants or fragrances can be added and mixed in.
7. Moulding: Pour the thick mixture into soap moulds (e.g., plastic containers, calabashes lined with cling film).
8. Curing: Cover and leave the soap to harden for 24-48 hours. Then remove from moulds and allow to "cure" in a well-ventilated area for several weeks. Curing allows excess water to evaporate, making the soap harder and milder. * Uses of Soap:
1. Personal Hygiene: Bathing, washing hands, shampooing hair.
2. Laundry: Washing clothes.
3. Household Cleaning: Washing dishes, cleaning surfaces, general sanitation.
4. Industrial Cleaning: In factories and workshops. This section provides detailed content for the teacher to deliver the lesson.
A. Introduction to Acids Definition: Acids are chemical substances that typically have a sour taste (e.g., lemon, vinegar). They are often corrosive, meaning they can eat away at certain materials, and they react in specific ways with other substances. A key characteristic is their ability to turn blue litmus paper red.
Physical Properties of Acids:
1. Sour Taste: (Caution: Students must never taste unknown substances. This property is for common, edible acids like fruits).
Examples: unripe mangoes, lemons, limes, vinegar.
2. Corrosive Nature: Strong acids can cause burns and damage materials like clothes, skin, and metals. For example, battery acid.
3. Effect on Litmus Paper: Acids turn blue litmus paper RE
D. They have no effect on red litmus paper.
4. Feel: May feel sticky if highly concentrated (but safe to avoid touching).
Types of Acids (Simplified for P5):
1. Organic Acids (Natural Acids): These are naturally occurring acids found in plants and animals. They are generally weaker and safer to handle (in diluted forms).
Examples relevant to Nigeria: Citric acid: Found in citrus fruits like oranges, lemons, limes, tangerines (e.g., 'Osan', 'Lemu', 'Tafasa').
Acetic acid: The acid in vinegar, used in cooking and preservation (e.g., pickling vegetables).
Lactic acid: Found in fermented milk products like 'wara' (Nigerian cheese curds) or natural yogurt.
Tartaric acid: Found in tamarind ('Tsamiya').
Oxalic acid: Found in sorrel leaves ('Zobo' leaves, 'Ishapa').
2. Mineral Acids (Inorganic Acids): These are stronger acids, often manufactured industrially or derived from minerals. They are highly corrosive and dangerous.
Examples relevant to Nigeria: Sulphuric acid: Used in car batteries (battery acid).
Hydrochloric acid: Found in the stomach for digestion; also used in some strong cleaning agents.
Nitric acid: Used in making fertilizers and explosives. (Emphasis on extreme caution for mineral acids).
Uses of Acids:
1. Food and Beverages: Provide flavour (sour taste), e.g., in drinks, unripe fruits.
2. Food Preservation: Vinegar is used to pickle foods like peppers, onions, and vegetables, extending their shelf life.
3. Digestion: Hydrochloric acid in the stomach helps digest food.
4. Industrial Uses: Sulphuric acid in car batteries, nitric acid in fertilizers, cleaning agents for rust removal.
B. Introduction to Bases Definition: Bases are chemical substances that often have a bitter taste (e.g., soap, some plant ashes). They feel slippery or soapy to the touch. A key characteristic is their ability to turn red litmus paper blue. Bases that dissolve in water are called alkalis.
Physical Properties of Bases:
1. Bitter Taste: (Caution: Students must never taste unknown substances).
Examples: soap, 'Aun Efun' or 'Kanwu' (potash) solution.
2. Slippery/Soapy Feel: Bases feel slippery when touched, like soap.
3. Corrosive Nature: Strong bases (like caustic soda) are also very corrosive and can cause severe burns.
4. Effect on Litmus Paper: Bases turn red litmus paper BLU
E. They have no effect on blue litmus paper.
Types of Bases (Simplified for P5):
1. Weak Bases: Generally found in natural materials or used in mild applications.
Examples relevant to Nigeria: Wood ash leachate: Water extracted from wood ash, containing potassium carbonate, used in traditional soap making.
Baking soda (Sodium bicarbonate): Used in cooking (e.g., for rising dough), as an antacid, and for cleaning.
2. Strong Bases: Highly corrosive, often industrially produced.
Examples relevant to Nigeria: Caustic Soda (Sodium Hydroxide): A very strong base, widely used in commercial and local soap making, and for drain cleaning.
Potash (Potassium Carbonate): A stronger natural base obtained by leaching ash from specific plant materials (e.g., cocoa pod ash, palm bunch ash). Known as 'Aun Efun' or 'Kanwu' in local markets. * Uses of Bases:
1. Soap Making: Essential for reacting with fats/oils to produce soap (saponification).
2. Cleaning Agents: Used in detergents, oven cleaners, drain cleaners due to their ability to dissolve grease and oil.
3. Neutralization: Antacids (which are bases) are used to neutralize excess stomach acid (an acid) to relieve heartburn.
4. Agriculture: Lime (calcium hydroxide, a base) is used to reduce soil acidity. *C. Distinguishing Between by leaching ash from specific plant materials (e.g., cocoa pod ash, palm bunch ash). Known as 'Aun Efun' or 'Kanwu' in local markets.
Uses of Bases:
1. Soap Making: Essential for reacting with fats/oils to produce soap (saponification).
2. Cleaning Agents: Used in detergents, oven cleaners, drain cleaners due to their ability to dissolve grease and oil.
3. Neutralization: Antacids (which are bases) are used to neutralize excess stomach acid (an acid) to relieve heartburn.
4. Agriculture: Lime (calcium hydroxide, a base) is used to reduce soil acidity. C. Distinguishing Between Acids and Bases (Indicators) The most common and safest way for Primary 5 students to distinguish between acids and bases is using litmus paper.
Blue litmus paper: Turns RED in an acidic solution.
Red litmus paper: Turns BLUE in a basic solution. If a substance does not change the colour of either red or blue litmus paper, it is considered neutral (e.g., pure water). Other natural indicators can be used for demonstration: Hibiscus flower extract: Turns red in acid, greenish-blue in base.
Turmeric powder extract: Turns yellow in acid, reddish-brown in base.
D. Local Soap Making Concept: Soap is formed when a fat or oil reacts with a strong base (alkali) in a process called saponification.
Local Materials Used in Making Soap:
1. Fats/Oils (Lipids): These provide the fatty acids needed for soap.
Palm oil ('Manja'): Widely available in Nigeria, gives soap a yellowish colour.
Coconut oil: Produces hard soap with good lather.
Groundnut oil ('Man Gyada'): Can also be used.
Shea butter ('Ori'): Adds moisturizing properties.
Animal fats: Tallow (from beef), Lard (from pork) – less common in traditional Nigerian soap making due to cultural/religious reasons, but possible.
2. Bases (Alkalis): These are the key reactive ingredients. Potash ('Aun Efun', 'Kanwu'): A naturally occurring form of potassium carbonate. It is obtained by burning plant materials (e.g., cocoa pods, palm fruit bunches, specific tree woods) to ash, then leaching the ash with water (filtering the water that passes through the ash). The resulting liquid (leachate) is a basic solution. This typically makes softer soaps.
Caustic Soda (Sodium Hydroxide): A strong, industrially manufactured base. It is a white, crystalline solid usually sold in flakes or pellets. It is much stronger than potash and typically produces harder soaps. (Extreme caution must be exercised when handling caustic soda).
3. Water: Used to dissolve the alkali.
4. Additives (Optional): Colourants: Natural dyes.
Fragrances: Essential oils, perfumes.
Exfoliants: E.g., oat powder, coffee grounds.
Glycerin: Often naturally produced during saponification, sometimes added for extra moisturization.
Active Ingredients in Local Soap Making: The active ingredients are the oil/fat and the alkali (potash or caustic soda). They react together to form soap. Simple Process of Making Soap from Local Materials (Demonstration/Observation):
1. Safety First: Teacher wears gloves and eye protection.
2. Prepare Alkali Solution: Using Potash: Dissolve crushed potash ('Kanwu') in a measured amount of water. Stir well and let it settle. Filter out any solids to get a clear basic solution (leachate).
Using Caustic Soda:* Carefully dissolve caustic soda flakes/pellets in a measured amount of water in a heat-resistant container. This reaction generates heat. Allow it to cool completely before use. (Supervise closely, or prepare beforehand).
3. Prepare Oil: Measure the required amount of palm oil or other fat. Gently warm it slightly to ensure it's liquid.
4. Mixing and Saponification: Slowly and carefully pour the cooled alkali solution into the warm oil while continuously stirring vigorously.
5. Trace: Continue stirring (can be done with a stick or mixer) until the mixture thickens and reaches "trace" – a point where the mixture leaves a visible mark when drizzled on its surface, like thin pudding.
6. Additives (Optional): At trace, any colourants or fragrances can be added and mixed in.
7. Moulding: Pour the thick mixture into soap moulds (e.g., plastic containers, calabashes lined with cling film).
8. Curing: Cover and leave the soap to harden for 24-48 hours. Then remove from moulds and allow to "cure" in a well-ventilated area for several weeks.
Phase 1: Introduction and Engagement (10 minutes)
Teacher Activity: Begins by asking students to name things they use daily that taste sour (e.g., lemon, vinegar) or feel slippery (e.g., soap). Introduces the terms "acids" and "bases" as the scientific names for these types of substances. Presents various safe household items (e.g., lemon, lime, vinegar, soap, baking soda solution, ash leachate) and asks students to identify their common properties.
Student Activity: Students name sour/slippery items. Students observe and (where safe) carefully smell or touch presented items (e.g., feel soap, feel lemon rind). Students share initial observations.
Phase 2: Exploration and Explanation (25 minutes)
Teacher Activity: Explains the definition and physical properties of acids, using the examples brought or drawing on student examples. Demonstrates the litmus paper test for acids (e.g., using lemon juice or vinegar on blue litmus paper). Explains the types of acids (organic/mineral) and provides relevant Nigerian examples and uses. Explains the definition and physical properties of bases, using the examples brought (e.g., soap, baking soda solution, ash leachate). Demonstrates the litmus paper test for bases (e.g., using soap solution or ash leachate on red litmus paper). Explains the types of bases (referring to strength generally, e.g., caustic soda vs. ash) and provides relevant Nigerian examples and uses. Guides a class discussion on how to safely distinguish between acids and bases using litmus paper.
Student Activity: Students actively listen, ask questions, and take notes. Students observe litmus paper demonstrations carefully. Students identify more examples of acids and bases from their environment. Students participate in discussions, suggesting ways to differentiate substances.
Phase 3: Practical Application - Local Soap Making (20 minutes for demonstration, plus discussion)
Teacher Activity: Introduces the concept of local soap making, highlighting its importance in Nigerian homes and economy.
Presents the local materials: palm oil, potash ('Kanwu') or caustic soda, water, and explains their roles. Demonstrates the soap-making process step-by-step (as outlined in Key Concepts, Section 2D). Emphasize safety precautions when handling alkalis (gloves, eye protection). This should be a teacher-led demonstration for safety. Explains that the oil (fat) and the alkali (potash/caustic soda) are the active ingredients that react to make soap. Discusses the various uses of soap.
Student Activity: Students observe the demonstration of soap making, paying attention to the materials, steps, and safety precautions. Students identify the local materials and the active ingredients used. Students ask questions about the process and materials. Students list and discuss the uses of soap.
Phase 4: Conclusion and Review (5 minutes)
Teacher Activity: Recap the main points of the lesson: what acids and bases are, their properties, examples, how to distinguish them, and the process of making and using soap. Addresses any remaining questions.
Student Activity: Students answer recap questions from the teacher. Students clarify any misconceptions.
Materials: Sample acids: Lemon, lime, vinegar, unripe mango, small bottle of battery acid (for demonstration only, sealed).
Sample bases: Bar soap, baking soda, wood ash leachate (prepared), small amount of caustic soda flakes (for demonstration only, sealed). Red and blue litmus papers. Gloves and eye protection for teacher (especially for soap making).
Materials for soap making demonstration: Palm oil, potash ('Kanwu') or caustic soda, water, mixing bowls, stirring rod/spoon, measuring cups, safety gear, small moulds (e.g., empty yoghurt cups). Chart or whiteboard for writing examples and properties.
Household Cleaning and Hygiene: Students learn that many cleaning products (like detergents, oven cleaners) are basic, while some rust removers or descalers are acidic. This knowledge helps them understand why certain cleaners work for specific tasks and the importance of not mixing them. The practical soap-making activity directly connects to personal hygiene and household cleaning in every Nigerian home, from traditional bar soap ('Ose dudu') to modern variants.
Food and Agriculture: The lesson integrates with students' understanding of nutrition and agriculture. Examples like sour fruits (citrus) as natural acids and the use of vinegar for food preservation are relatable. The concept of soil acidity (sour soil) and its neutralization with bases (like lime) is crucial for understanding farming practices, especially in regions with naturally acidic soils common in parts of Southern Nigeria, affecting crop yields for staple foods like cassava, yam, and maize.
Traditional Nigerian Medicine/Practices: The use of wood ash leachate (a base) in traditional medicine or for softening food like 'ewedu' (jute leaves) or 'okro' provides a cultural link. Understanding potash ('Kanwu' / 'Aun Efun') as a strong base in local food preparation (e.g., in some soups, for softening beans) or for traditional soap making highlights the scientific principles behind long-standing cultural practices.