Lesson Notes By Weeks and Term v4 - JHS 3

Lesson Video

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Performance objectives

• Define acids and identify their common characteristics.
• List common acids and their everyday uses.
• Explain the pH scale and its relation to acid strength.
• Use indicators to identify acids.
• Discuss safety measures for handling acids.

Lesson summary

In JHS Science under Materials (Diversity of Matter), learners meet substances such as acids, bases and salts found in everyday Ghanaian life—lime/lemon, vinegar, battery water, soft drinks, soap, washing soda, and antacids. Understanding the characteristics of common acids helps learners to: handle household and laboratory chemicals safely, interpret warning labels (corrosive/irritant), explain everyday observations (e.g., why lime removes rust stains, why acids react with metals), connect Science to farming, sanitation, food processing, and industry in Ghana.

Lesson notes

2.1 What is an acid? An acid is a substance that: produces hydrogen ions (H⁺) when dissolved in water, or donates protons (H⁺) to another substance (advanced idea).

Important note (JHS level): We usually test acids by their observable characteristics rather than memorising definitions. Examples of common acids (Ghanaian context) | Common acid | Where found / example | Main use / relevance | |---|---|---| | Citric acid | lime, lemon, oranges | flavouring, cleaning stains, preserving | | Ethanoic acid (acetic acid) | vinegar | food preservation, cooking, cleaning | | Carbonic acid | soft drinks (fizzy drinks) | causes sour taste and fizz (with CO₂) | | Hydrochloric acid | stomach acid; some toilet cleaners (dilute) | digestion; cleaning (handle carefully) | | Sulfuric acid | car battery acid | batteries (very corrosive) |

2.2 Characteristics of common acids (core of the indicator) (A) Sour taste (do not taste in the lab) Many acids taste sour (e.g., lime, lemon, vinegar). Safety rule: Never taste unknown chemicals in the laboratory. (B) pH less than 7 Acids have pH values below 7. Strong acids: pH 0–3 Weak acids: pH 4–6

Evaluation guide

• Identify acids, bases and salts by their characteristics.
• Create a model of a pH Scale and use it to determine the strength of
• common acids and alkali solutions using indicators. Critical Thinking and Problem Solving (CP),
• Communication and Collaboration (CC),