IGCSE, Edexcel, IB and AP Science Courses | Dr Dabour Hub Academy

Overview

🎯 Learning outcomes

Classify chemical compounds into acids, bases (alkalis), oxides, and salts according to their composition and dissociation in water.
Explain the properties of acids (sour taste, releasing H⁺ ions, turning litmus red) and bases (bitter taste, slippery feel, releasing OH⁻ ions, turning litmus blue).
Classify oxides into basic oxides (metal oxides), acidic oxides (non-metal oxides), and amphoteric oxides.
Understand the pH scale from 0 to 14 and interpret acidic (pH < 7), neutral (pH = 7), and basic (pH > 7) solutions.
Formulate neutralization reactions and identify soluble and insoluble salts in water.

🌳 Concept tree

Lesson 2 – Acids
Bases
Salts
Oxides and pH Scale

├── Key terms

├── Laws and key relationships

├── Classification of CompoundsAcids and Bases

├── OxidesBasic, Acidic, and Neutralization Chemistry

├── The pH Scale and Salts Chemistry

├── Comparison

├── Worked examples

└── Exam tips

Lesson 2 – Acids, Bases, Salts, Oxides and pH Scale · 1 / 12

Key terms

Comparison aspect	Main idea	Keywords
Acids	Substances that dissociate in aqueous solution to release positive hydrogen ions (H⁺ or hydronium H₃O⁺), producing a sour taste and turning blue litmus paper red.	Substancesdissociateaqueoussolution
Bases and Alkalis	Bases are metal oxides or hydroxides that neutralize acids; an alkali is a water-soluble base that dissociates to release hydroxide ions (OH⁻), turning red litmus blue.	metaloxideshydroxidesneutralize
Neutralization Reaction	A fundamental chemical reaction between an acid and a base to produce salt and water: Acid + Base → Salt + Water	fundamentalchemicalbetweenacid
pH Scale	A numerical scale ranging from 0 to 14 measuring the acidity or alkalinity of an aqueous solution: pH < 7 is acidic pH = 7 is neutral and pH > 7 is basic/alkaline	numericalrangingmeasuringacidity
Basic Oxides	Metal oxides that react with acids to form salt and water (e.g., Na₂O, CaO, CuO); those that dissolve in water form alkalis.	Metalreactacidsform
Acidic Oxides (Acid Anhydrides)	Non-metal oxides that dissolve in water to form acids (e.g., CO₂, SO₃, P₂O₅) and react with bases to form salt and water.	metaldissolvewaterform

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Laws and key relationships

Arrhenius Acid-Base Dissociation[ Formula: Acid: HCl(aq) → H⁺(aq) + Cl⁻(aq) | Base: NaOH(aq) → Na⁺(aq) + OH⁻(aq) ] Defines acids and bases in aqueous media.

Neutralization General Formulation[ Formula: H⁺(aq) + OH⁻(aq) — → H₂O(l) ] Net ionic equation of acid-base neutralization.

pH Definition[ Formula: pH = -log10 [H+] | pH + pOH = 14 ] At 25°C in aqueous solutions.

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Classification of Compounds: Acids and Bases

Chemical compounds are categorized into four major families→acids, bases, oxides, and salts.

AcidsCharacterized by a chemical formula beginning with hydrogen (except organic acids which end in -COOH).

ExamplesHydrochloric acid (HCl), Sulfuric acid (H2SO4), Nitric acid (HNO3).

Physical and chemical propertiessour taste, corrosive to metals (releasing flammable hydrogen gas: Zn + 2HCl → ZnCl2 + H2↑), and turning litmus paper red.

Comparison aspect	Main idea	Keywords
Bases and Alkalis	An alkali is a subset of bases that dissolve in water to produce hydroxide ions (OH−)	subsetdissolvewaterproduce
Famous rule	All alkalis are bases but not all bases are alkalis!	alkalisbases
•	(For example, CuO and Fe(OH)₃ are bases that do not dissolve in water, hence they are not alkalis).	examplebasesdissolvewater
Properties	bitter taste soapy feel and turning litmus paper blue	bittertastesoapyfeel

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Oxides: Basic, Acidic, and Neutralization Chemistry

Oxides are binary compounds formed by the combination of an element with oxygen:

Comparison aspect	Main idea	Keywords
Basic Oxides	Oxides of metals (e.g MgO CaO Na2O). Basic oxides that dissolve in water form alkaline solutions: Na2O + H2O → 2NaOH. Basic oxides react with acids to produce salt and water: CuO + H2SO4 → CuSO4 + H2O	metalsNa2Odissolvewater
Acidic Oxides	Oxides of non-metals (e.g CO2 SO2 SO3). When dissolved in water they yield acids: CO2 + H2O → H2CO3 (carbonic acid) SO3 + H2O → H2SO4 (sulfuric acid). Acidic oxides react with alkalis to form salt and water: CO2 + Ca(OH)2 → CaCO3↓ + H2O (turbidity in limewater)	metalsdissolvedwateryield
Amphoteric Oxides	Oxides that react with acids as bases and with bases as acids producing salt and water in both cases (e.g Al2O3 ZnO SnO PbO)	reactacidsbasesproducing

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The pH Scale and Salts Chemistry

The pH Scale→Developed by Sørensen to express hydrogen ion concentration conveniently:

Comparison aspect	Main idea	Keywords
Strongly acidic	pH 0 to 3 (e.g gastric juice battery acid)	gastricjuicebattery
Weakly acidic	pH 4 to 6 (e.g vinegar coffee milk)	vinegarcoffeemilk
Neutral	pH 7.0 (pure distilled water at 25°C)	puredistilledwater
Weakly basic	pH 8 to 10 (e.g baking soda sea water)	bakingsodawater
Strongly basic	pH 11 to 14 (e.g bleach drain cleaner NaOH)	bleachdraincleanerNaOH
Salts	Ionic compounds composed of a positive metallic cation and a negative acid radical anion. Classification by solubility	Ioniccompoundscomposedpositive

Soluble SaltsAll nitrates (NO3−), all acetates (CH3COO-), all sodium (Na+), potassium (K+), and ammonium (NH4+) salts.

Insoluble Salts (Precipitates)Silver chloride (AgCl, white), Lead iodide (PbI2, yellow), Barium sulfate (BaSO4, white), Calcium carbonate (CaCO3, white).

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Comparison

Table→Comparative Distinction Between Acids and Bases (Alkalis)

Property / Characteristic	Acids	Bases / Alkalis
Ion released in aqueous solution	Hydrogen ion (H⁺ / H₃O⁺)	Hydroxide ion (OH⁻)
Taste and physical texture	Sour taste, sharp sting	Bitter taste, slippery / soapy feel
Effect on Litmus Paper	Turns blue litmus paper RED	Turns red litmus paper BLUE
Effect on Phenolphthalein	Colorless	Deep pink / Magenta
Reaction with Carbonates	Effervescence with CO₂ gas release	No reaction
Common Laboratory Examples	HCl, H₂SO₄, HNO₃, CH₃COOH	NaOH, KOH, Ca(OH)₂, NH₄OH

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Worked examples

Identifying Reaction Types and Predicting Salt FormationProblem Statement & Given Data: Write the balanced chemical equations for the following reactions and state the type of reaction: (1) Hydrochloric acid with sodium hydroxide, (2) Carbon dioxide with limewater, (3) Zinc metal with dilute sulfuric acid. Step-by-Step Mathematical & Chemical Solution: [1] Reaction 1: Acid + Base Neutralization: [2] HCl(aq) + NaOH(aq) — → NaCl(aq) + H₂O(l). [3] Type: Neutralization / Double displacement; produces sodium chloride salt and water. [4] Reaction 2: Acidic Oxide with Base: [5] CO₂(g) + Ca(OH)₂(aq) — → CaCO₃(s)↓ + H₂O(l). [6] Type: Precipitation; forms white insoluble calcium carbonate precipitate causing limewater turbidity. [7] Reaction 3: Metal with Acid Single Displacement: [8] Zn(s) + H₂SO₄(aq) — → ZnSO₄(aq) + H₂(g)↑. [9] Type: Single displacement; produces zinc sulfate salt and flammable hydrogen gas which pops with a lighted splint.💡 High-Yield Exam Shortcut & Pitfall Alert: Exam Tip: All neutralization reactions produce Salt + Water!

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Exam tips

All alkalis are bases, but not all bases are alkalis (only water-soluble bases are alkalis).
The pH of acids is less than 7, neutral is 7, and alkalis is greater than 7.
Acids turn blue litmus red; alkalis turn red litmus blue.
Metal oxides are basic; non-metal oxides are acidic; Al₂O₃ and ZnO are amphoteric.
All sodium, potassium, ammonium, and nitrate salts dissolve completely in water.
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Key Scientific Tables & Anatomical Diagrams Extracted from Official Curricula

💡 Core Diagrams & Reference Data→All data, reference comparison tables, and anatomical figures have been accurately digitized from official curriculum textbooks.

🔬 pH_Scale_Acids_and_Bases

Scientific details and precise observational breakdown:
The pH Scale (0 to 14) Acids, Neutral Solutions, and Bases (pH = —!0910 [H ])
Battery Gastric Lemon Vinegar Pure Baking Milk of Ammonia Soapy NaOH
Acid HCl Juice CH₃COOH = Tomato Coffee Milk Water Blood Soda Magnesia NH₃ Water Bleach Drain

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Increasing Acidity ([H+] increases) Neutral (pH=7) Increasing Basicity / Alkalinity ([OH-] increases)

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Part 11

📖

Lesson 2 – Acids, Bases, Salts, Oxides and pH Scale · 11 / 12

🔍 In-Depth Explanations, Deductions & Multi-Book Insights:

★ Comprehensive Ministry-Approved Academic Textbook 2026 / 2027 ★
Textbook Chapter Acids, Bases, Salts, Oxides and pH Scale
First Preparatory / Grade 7 | Unit 1 – Chemical Reactions and Matter | Modern Egyptian Curriculum 2026/2027
🎯 Ministerial Learning Outcomes & Key Competencies 2026/2027:
• Classify chemical compounds into acids, bases (alkalis), oxides, and salts according to their composition and dissociation in water.
• Explain the properties of acids (sour taste, releasing H⁺ ions, turning litmus red) and bases (bitter taste, slippery feel, releasing OH⁻ ions, turning litmus blue).
• Classify oxides into basic oxides (metal oxides), acidic oxides (non-metal oxides), and amphoteric oxides.

• Understand the pH scale from 0 to 14 and interpret acidic (pH < 7), neutral (pH = 7), and basic (pH > 7) solutions.
• Formulate neutralization reactions and identify soluble and insoluble salts in water.
📖 Core Scientific Terminology & Definitions:
🔹 Acids Substances that dissociate in aqueous solution to release positive hydrogen ions (H+ or hydronium H3O+), producing a sour taste and turning blue litmus paper red.
🔹 Bases and Alkalis Bases are metal oxides or hydroxides that neutralize acids; an alkali is a water-soluble base that dissociates to release hydroxide ions (OH−), turning red litmus blue.
🔹 Neutralization Reaction A fundamental chemical reaction between an acid and a base to produce salt and water: Acid + Base → Salt + Water.

Comparison aspect	Main idea	Keywords
🔹 pH Scale	A numerical scale ranging from 0 to 14 measuring the acidity or alkalinity of an aqueous solution: pH < 7 is acidic pH = 7 is neutral and pH > 7 is basic/alkaline	numericalrangingmeasuringacidity
🔹 Basic Oxides	Metal oxides that react with acids to form salt and water (e.g Na2O CaO CuO) those that dissolve in water form alkalis	Metalreactacidsform
🔹 Acidic Oxides (Acid Anhydrides)	Non-metal oxides that dissolve in water to form acids (e.g CO2 SO3 P2O5) and react with bases to form salt and water	metaldissolvewaterform
•	⚖️ Governing Mathematical & Physical Laws and Principles	GoverningMathematicalPhysicalLaws
★ Arrhenius Acid-Base Dissociation	[ Formula: Acid: HCl(aq) → H+(aq) + Cl−(aq) \| Base: NaOH(aq) → Na+(aq) + OH−(aq) ] Defines acids and bases in aqueous media	FormulaNaOHDefinesacids

Comparison aspect	Main idea	Keywords
★ Neutralization General Formulation	[ Formula: H+(aq) + OH−(aq) — → H2O(l) ] Net ionic equation of acid-base neutralization	ionicequationacidbase
★ pH Definition	[ Formula: pH = -log10 [H+] \| pH + pOH = 14 ] At 25°C in aqueous solutions	Formulalog10aqueoussolutions
•	📌 Exhaustive In-Depth Academic Explanation & Scientific Analysis	ExhaustiveDepthAcademicExplanation

1. Classification of Compounds: Acids and Bases

Comparison aspect	Main idea	Keywords
Chemical compounds are categorized into four major families	acids bases oxides and salts	acidsbasesoxidessalts
Acids	Characterized by a chemical formula beginning with hydrogen (except organic acids end in -COOH). Examples: Hydrochloric acid (HCl) Sulfuric acid (H2SO4) Nitric acid (HNO3). Physical and chemical properties: sour taste corrosive to metals (releasing flammable hydrogen gas: Zn + 2HCl → ZnCl2 + H2↑) and turning litmus paper red	Characterizedchemicalformulabeginning

Bases and Alkalis→An alkali is a subset of bases that dissolve in water to produce hydroxide ions (OH−). Famous rule: All alkalis are bases, but not all bases are alkalis! (For example, CuO and Fe(OH)3 are bases that do not dissolve in water, hence they are not alkalis). Properties: bitter taste, soapy feel, and turning litmus paper blue.

2. Oxides: Basic, Acidic, and Neutralization Chemistry

Oxides are binary compounds formed by the combination of an element with oxygen:

3. The pH Scale and Salts Chemistry

The pH ScaleDeveloped by Sørensen to express hydrogen ion concentration conveniently:

– Strongly acidicpH 0 to 3 (e.g., gastric juice, battery acid).

Comparison aspect	Main idea	Keywords
– Weakly acidic	pH 4 to 6 (e.g vinegar coffee milk)	vinegarcoffeemilk
– Neutral	pH 7.0 (pure distilled water at 25°C)	puredistilledwater
– Weakly basic	pH 8 to 10 (e.g baking soda sea water)	bakingsodawater
– Strongly basic	pH 11 to 14 (e.g bleach drain cleaner NaOH)	bleachdraincleanerNaOH
Salts	Ionic compounds composed of a positive metallic cation and a negative acid radical anion. Classification by solubility	Ioniccompoundscomposedpositive
– Soluble Salts	All nitrates (NO3−) all acetates (CH3COO-) all sodium (Na+) potassium (K+) and ammonium (NH4+) salts	nitratesacetatesCH3COOsodium
– Insoluble Salts (Precipitates)	Silver chloride (AgCl white) Lead iodide (PbI2 yellow) Barium sulfate (BaSO4 white) Calcium carbonate (CaCO3 white)	SilverchlorideAgClwhite

📊 Detailed Comparative Analysis & Data Classifications:
Table Comparative Distinction Between Acids and Bases (Alkalis)
✏️ Step-by-Step Fully Solved Exemplary Numerical Problems & Proofs:
★ Identifying Reaction Types and Predicting Salt Formation
Problem Statement & Given Data Write the balanced chemical equations for the following reactions and state the type of reaction: (1) Hydrochloric acid with sodium hydroxide, (2) Carbon dioxide with limewater, (3) Zinc metal with dilute sulfuric acid.
Step-by-Step Mathematical & Chemical Solution:
[1] Reaction 1 Acid + Base Neutralization:
[2] HCl(aq) + NaOH(aq) — → NaCl(aq) + H₂O(l).
[3] Type Neutralization / Double displacement; produces sodium chloride salt and water.
[4] Reaction 2 Acidic Oxide with Base:
[5] CO₂(g) + Ca(OH)₂(aq) — → CaCO₃(s)↓ + H₂O(l).
[6] Type Precipitation; forms white insoluble calcium carbonate precipitate causing limewater turbidity.
[7] Reaction 3 Metal with Acid Single Displacement:
[8] Zn(s) + H₂SO₄(aq) — → ZnSO₄(aq) + H₂(g)↑.
[9] Type Single displacement; produces zinc sulfate salt and flammable hydrogen gas which pops with a lighted splint.
💡 High-Yield Exam Shortcut & Pitfall Alert Exam Tip: All neutralization reactions produce Salt + Water!

Property / Characteristic	Acids	Bases / Alkalis
Ion released in aqueous solution	Hydrogen ion (H⁺ / H₃O⁺)	Hydroxide ion (OH⁻)
Taste and physical texture	Sour taste, sharp sting	Bitter taste, slippery / soapy feel
Effect on Litmus Paper	Turns blue litmus paper RED	Turns red litmus paper BLUE
Effect on Phenolphthalein	Colorless	Deep pink / Magenta
Reaction with Carbonates	Effervescence with CO₂ gas release	No reaction
Common Laboratory Examples	HCl, H₂SO₄, HNO₃, CH₃COOH	NaOH, KOH, Ca(OH)₂, NH₄OH

💡 💡 Essential Exam Traps, Tips & High-Yield Insights:

All alkalis are bases, but not all bases are alkalis (only water-soluble bases are alkalis).
The pH of acids is less than 7, neutral is 7, and alkalis is greater than 7.
Acids turn blue litmus red; alkalis turn red litmus blue.
Metal oxides are basic; non-metal oxides are acidic; Al₂O₃ and ZnO are amphoteric.
All sodium, potassium, ammonium, and nitrate salts dissolve completely in water.

Lesson 2 – Acids, Bases, Salts, Oxides and pH Scale · 12 / 12

Curriculum

Science

Unit 1 - Periodic Motion and Wave Mechanics

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Lesson 2 – Acids, Bases, Salts, Oxides and pH Scale