Class 10 Science Chapter 2: Acids, Bases and Salts - Summary

Of course! Here is a comprehensive summary of CBSE Class 10 Science Chapter 2: Acids, Bases and Salts.

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Class 10 Science - Chapter 2: Acids, Bases and Salts - Summary

Part 1: Understanding the Basics

1. Acids

* Definition: Substances that release hydrogen ions (H⁺) in aqueous solution.

* Source: The word 'acid' comes from the Latin acidus, meaning sour. Many sour foods contain acids.

* Examples:

* Organic Acids: Citric acid (citrus fruits), Acetic acid (vinegar), Lactic acid (curd), Oxalic acid (tomatoes).

* Mineral Acids: Hydrochloric acid (HCl), Sulphuric acid (H₂SO₄), Nitric acid (HNO₃). These are strong and corrosive.

2. Bases

* Definition: Substances that release hydroxide ions (OH⁻) in aqueous solution. They are bitter in taste and soapy to touch.

* Examples: Sodium hydroxide (NaOH), Calcium hydroxide [Ca(OH)₂] (lime water), Potassium hydroxide (KOH).

* Alkalis: Water-soluble bases are called alkalis (e.g., NaOH, KOH). Not all bases are alkalis (e.g., CuO is a base but insoluble in water).

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Part 2: Chemical Properties and Reactions

1. Reactions of Acids and Bases with Metals

* Acid + Metal → Salt + Hydrogen gas

* `Zn + H₂SO₄ → ZnSO₄ + H₂`

* Test for H₂ Gas: Burns with a 'pop' sound.

* Base + Metal → Salt + Hydrogen gas

* `2NaOH + Zn → Na₂ZnO₂ (Sodium zincate) + H₂` (Only with amphoteric metals like Zn and Al)

2. Reaction of Metal Carbonates and Metal Hydrogencarbonates with Acids

* Acid + Metal Carbonate/Metal Hydrogencarbonate → Salt + CO₂ + H₂O

* `2HCl + Na₂CO₃ → 2NaCl + H₂O + CO₂`

* `HCl + NaHCO₃ → NaCl + H₂O + CO₂`

* Test for CO₂ Gas: Turns lime water milky. `Ca(OH)₂ + CO₂ → CaCO₃ (milky) + H₂O`

#### 3. Reaction of Acids and Bases with each other (Neutralization Reaction)

* Acid + Base → Salt + Water + Heat

* `NaOH + HCl → NaCl + H₂O`

* This reaction is exothermic.

4. Reaction of Metallic Oxides with Acids

* Metallic Oxide + Acid → Salt + Water

* `CuO + H₂SO₄ → CuSO₄ + H₂O`

Metallic oxides are *basic** in nature.

#### 5. Reaction of Non-Metallic Oxides with Bases

* Non-Metallic Oxide + Base → Salt + Water

* `Ca(OH)₂ + CO₂ → CaCO₃ + H₂O`

Non-metallic oxides are *acidic** in nature.

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Part 3: Important Concepts and Theories

1. What do all Acids and Bases have in common?

All acids provide H⁺ ions in water, and all bases provide OH⁻ ions in water. This led to the Arrhenius theory of acids and bases.

2. pH Scale

* A scale from 0 to 14 to measure the strength of acidic or basic solutions.

* pH < 7: Acidic solution

* pH = 7: Neutral solution

* pH > 7: Basic solution

* Importance:

* In Digestion: HCl in stomach (pH ~1.5) helps in digestion.

* Tooth Decay: pH lower than 5.5 can cause tooth decay.

* Soil pH: Plants require a specific pH range for healthy growth.

* Self-defense by Animals: Bees and ants inject methanoic acid (formic acid) causing burning pain.

3. Importance of pH in Everyday Life

* Acid Rain: pH of rain water is ~5.6. When it drops below 5.6, it becomes acid rain, harmful for aquatic life and buildings.

* pH in our body: Blood pH is tightly regulated around 7.4.

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### Part 4: Salts

#### 1. What are Salts?

* A salt is a compound formed when the H⁺ ion of an acid is replaced by a metal ion (or ammonium ion).

* Family of Salts: Salts having the same positive or negative ions belong to a family. E.g., NaCl, KCl, LiCl.

* Normal Salts: Formed by complete neutralization (e.g., NaCl).

* Acid Salts: Formed by partial replacement of H⁺ ions (e.g., NaHCO₃).

* Basic Salts: Formed by partial replacement of OH⁻ ions (e.g., Basic copper carbonate).

2. pH of Salts

* Salt of Strong Acid + Strong Base → Neutral (pH = 7) e.g., NaCl

* Salt of Strong Acid + Weak Base → Acidic (pH < 7) e.g., NH₄Cl

* Salt of Weak Acid + Strong Base → Basic (pH > 7) e.g., CH₃COONa

3. Common Chemicals from Common Salt (NaCl)

Sodium chloride (common salt) is used as a raw material for preparing various chemicals:

* Sodium Hydroxide (NaOH): `2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂` (Chlor-alkali process)

* Baking Soda (Sodium Hydrogencarbonate - NaHCO₃): `NaCl + NH₃ + H₂O + CO₂ → NaHCO₃ + NH₄Cl`

* Uses: Antacid, in baking, in fire extinguishers.

* Washing Soda (Sodium Carbonate - Na₂CO₃·10H₂O): `2NaHCO₃ → Na₂CO₃ + H₂O + CO₂` (on heating) then `Na₂CO₃ + 10H₂O → Na₂CO₃·10H₂O`

* Uses: Cleaning agent, water softener, in glass and paper industries.

* Bleaching Powder (CaOCl₂): `Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O`

* Uses: Bleaching cotton and linen, disinfecting drinking water.

* Plaster of Paris (POP - CaSO₄·½H₂O): `2(CaSO₄·2H₂O) → 2(CaSO₄)·½H₂O + 3H₂O` (on heating at 373K)

* Uses: Making casts for statues and broken limbs, plastering walls.

* Property: On mixing with water, it sets into a hard mass: `2(CaSO₄)·½H₂O + 3H₂O → 2(CaSO₄·2H₂O)` (Gypsum)

4. Water of Crystallization

* The fixed number of water molecules present in the crystal structure of a salt.

* Examples:

* Copper Sulphate (CuSO₄·5H₂O) - Blue crystals

* Gypsum (CaSO₄·2H₂O)

* Washing Soda (Na₂CO₃·10H₂O)

* On heating, salts lose their water of crystallization and become anhydrous, often changing color.

--- Key Points to Remember for Exams

* Acids are H⁺ donors, bases are OH⁻ donors.

The reaction between an acid and a base is called *neutralization**.

The *pH scale** measures the acidity or basicity of a solution.

* Salts are products of neutralization reactions.

* Common salt (NaCl) is a source for many important sodium compounds.

* Water of Crystallization gives salts their crystalline shape and specific properties.

### Summary: Class 10 Science CBSE

Chapter: Metals and Non-Metals (NCERT)

#### 1. Physical Properties of Metals & Non-Metals

| Property | Metals | Non-Metals |

|-----------------------|-------------------------------------|-------------------------------------|

| Physical State | Mostly solid (except Hg) | Solid, liquid (Br), or gas |

| Lustre | Shiny (metallic lustre) | Dull (except iodine, diamond) |

| Hardness | Hard (except Na, K) | Generally soft (except diamond) |

| Malleability | Malleable (can be beaten into sheets)| Non-malleable |

| Ductility | Ductile (drawn into wires) | Non-ductile |

| Conductivity | Good conductors of heat & electricity| Poor conductors (except graphite) |

| Density | High (except Na, K) | Low |

| Melting & Boiling Point| Generally high | Generally low |

| Sonority | Sonorous (ringing sound when struck)| Non-sonorous |

Exceptional Cases

- Graphite (non-metal) → good conductor of electricity

- Diamond (non-metal) → extremely hard

- Iodine → shiny

- Sodium, Potassium → soft, low density, low melting point

#### 2. Chemical Properties of Metals

1. Reaction with Oxygen

Metals + O₂ → Metal oxides (basic oxides)

Example:

4Na + O₂ → 2Na₂O (sodium oxide)

2Mg + O₂ → 2MgO (magnesium oxide)

→ Basic oxides react with water to form alkalis.

MgO + H₂O → Mg(OH)₂ (magnesium hydroxide)

2. Reaction with Water

- Reactive metals (K, Na, Ca):

2K + 2H₂O → 2KOH + H₂↑

2Na + 2H₂O → 2NaOH + H₂↑

- Less reactive (Mg, Al, Zn, Fe): react with steam

3Fe + 4H₂O → Fe₃O₄ + 4H₂↑

3. Reaction with Acids

Metal + Dilute acid → Salt + Hydrogen gas

Example:

Zn + 2HCl → ZnCl₂ + H₂↑

Mg + H₂SO₄ → MgSO₄ + H₂↑

(Metals above hydrogen in reactivity series displace H₂)

4. Reaction with Solutions of Other Metal Salts (Displacement Reaction)

More reactive metal displaces less reactive metal from its salt.

Example:

Fe + CuSO₄ → FeSO₄ + Cu (iron displaces copper)

Zn + CuSO₄ → ZnSO₄ + Cu (blue colour fades)

#### 3. Reactivity Series of Metals

K > Na > Ca > Mg > Al > Zn > Fe > Sn > Pb > H > Cu > Ag > Au

(Most reactive → Least reactive)

#### 4. Chemical Properties of Non-Metals

- Form acidic or neutral oxides with oxygen

C + O₂ → CO₂ (acidic)

S + O₂ → SO₂ (acidic)

- Do not displace hydrogen from acids

- Non-metals are electron acceptors (form anions)

#### 5. Occurrence of Metals

- Metals found in earth’s crust as minerals

- Highly reactive metals → combined state (oxides, carbonates, sulphides)

- Less reactive (Au, Pt) → free state (native)

#### 6. Extraction of Metals (Metallurgy)

Steps:

1. Enrichment of ore (remove impurities)

2. Extraction of metal (depends on reactivity)

- High reactive (K, Na, Ca, Mg, Al) → Electrolytic reduction

- Moderately reactive (Zn, Fe, Pb, Cu) → Reduction with carbon (roasting + smelting)

- Low reactive (Hg, Ag, Au) → By heating ore alone or with carbon

3. Refining → Purification (mostly electrolytic refining)

Important Processes:

- Roasting: Heating sulphide ore in air → oxide

2ZnS + 3O₂ → 2ZnO + 2SO₂

- Calcination: Heating carbonate ore in limited air → oxide

ZnCO₃ → ZnO + CO₂

- Smelting: Reduction of oxide with carbon in blast furnace (for Fe)

#### 7. Corrosion

Slow eating away of metal due to attack of atmospheric gases (O₂, moisture, CO₂).

Example:

- Rusting of iron: Fe + O₂ + H₂O → Fe₂O₃.xH₂O (hydrated iron oxide)

- Silver blackening: Ag + H₂S → Ag₂S (black)

- Green coating on copper: Cu + CO₂ + H₂O + O₂ → Cu(OH)₂.CuCO₃ (basic copper carbonate)

#### 8. Prevention of Corrosion

- Painting

- Oil/grease coating

- Galvanisation (coating with zinc)

- Alloying (e.g., stainless steel = Fe + Cr + Ni)

- Anodising (for aluminium)

#### 9. Alloys

Homogeneous mixture of two or more metals (or metal + non-metal).

Alloys are harder, more resistant to corrosion than pure metals.

| Alloy | Composition | Property/Use |

|----------------|------------------------------------|----------------------------------|

| Steel | Fe + C | Strong, used in construction |

| Stainless steel| Fe + Cr + Ni | Corrosion resistant |

| Brass | Cu + Zn | Decorative items, utensils |

| Bronze | Cu + Sn | Statues, coins |

| Solder | Pb + Sn | Joining wires |

| Amalgam | Metal + Hg | Dental fillings (with Ag, Sn) |

### Detailed Summary of "Carbon and its Compounds" (Chapter 4 from Science Textbook)

This PDF document is Chapter 4 from a Class 10-level science textbook (likely NCERT-based, reprint 2025-26), spanning 21 pages (book pages 58-78). It introduces carbon as a versatile element, explores its bonding, properties, compounds, and applications. The chapter includes activities, diagrams, electron dot structures, tables, and questions to reinforce concepts. Below is a detailed section-wise summary, covering key concepts, examples, activities, and explanations.

#### 1. Introduction to Carbon and Its Importance (Pages 1-2, Book pp. 58-59)

- Overview: Carbon is essential for life and everyday items. The chapter begins with an activity to list and categorize items used in daily life (e.g., metals, glass/clay, others). Most "others" are carbon-based compounds.

- Key Facts: Earth's crust has 0.02% carbon (as minerals like carbonates, coal, petroleum); atmosphere has 0.03% CO₂. Despite low abundance, carbon's versatility makes it crucial for food, clothes, medicines, and living structures.

- Activity 4.1: List 10 items used since morning, sort them, and identify carbon compounds. Test for carbon by burning (produces CO₂, confirmed by limewater turning milky).

- Properties Comparison: Carbon compounds have low melting/boiling points (e.g., acetic acid: 290 K mp, 391 K bp; methane: 90 K mp, 111 K bp) and are poor conductors of electricity, unlike ionic compounds.

#### 2. Bonding in Carbon – The Covalent Bond (Pages 2-4, Book pp. 59-61)

- Electronic Configuration: Carbon (atomic number 6) has 4 valence electrons (configuration: 2,4). It forms covalent bonds by sharing electrons to achieve noble gas configuration (octet), rather than gaining/losing 4 electrons (which is energetically unfavorable).

- Covalent Bonds: Shared electrons form single, double, or triple bonds. Examples:

- H₂: Single bond (electron dot: H• + •H → H:H).

- Cl₂: Single bond.

- O₂: Double bond (O=O).

- N₂: Triple bond (N≡N).

- H₂O: Single bonds (O with two H).

- NH₃: Single bonds (N with three H).

- CH₄: Single bonds (C with four H).

- Properties: Covalent compounds have low mp/bp due to weak intermolecular forces and are non-conductors (no ions).

- Allotropes of Carbon (Page 4, Book p. 61): Different forms with varying structures:

- Diamond: Rigid 3D structure (each C bonded to 4 others); hardest substance, non-conductor.

- Graphite: Hexagonal layers (each C bonded to 3 others, with one double bond); soft, slippery, good conductor.

- Fullerene: e.g., C₆₀ (buckminsterfullerene, football-shaped); synthetic diamonds made under high pressure/temperature.

- Questions: Electron dot for CO₂ and S₈ (ring).

#### 3. Versatile Nature of Carbon (Pages 5-6, Book pp. 62-63)

- Reasons for Versatility:

- Catenation: Carbon forms long chains, branches, or rings via single/double/triple bonds (strong C-C bonds; silicon chains are shorter and reactive).

- Tetravalency: Bonds with 4 other atoms (C or heteroatoms like O, H, N, S, Cl).

- Saturated vs. Unsaturated: Saturated (single bonds, alkanes); unsaturated (double/triple bonds, alkenes/alkynes, more reactive).

- Organic Compounds Note: Originally thought to require "vital force" (from living systems); disproved by Wöhler (1828, synthesized urea from ammonium cyanate). Now includes all C-compounds except oxides, carbonates, etc.

#### 4. Saturated and Unsaturated Carbon Compounds (Pages 6-7, Book pp. 63-64)

- Saturated (Alkanes): e.g., Ethane (C₂H₆): Step-by-step structure (C-C, add H to satisfy valencies).

- Unsaturated: e.g., Ethene (C₂H₄, double bond); Ethyne (C₂H₂, triple bond).

- Table 4.2: Formulas and structures for methane (CH₄) to hexane (C₆H₁₄).

- Activity 4.2: Generate homologous series for functional groups.

#### 5. Chains, Branches, and Rings (Pages 7-8, Book pp. 64-65)

- Chains: Straight (e.g., butane: C₄H₁₀) or branched (isomers with same formula but different structures).

- Rings: Cyclic, e.g., cyclohexane (C₆H₁₂), benzene (C₆H₆, unsaturated with alternating double bonds).

- Hydrocarbons: Only C and H; alkanes (saturated), alkenes (double), alkynes (triple).

- Heteroatoms: Replace H in chains (e.g., halogens, O, N), forming functional groups (Table 4.3: halo (-Cl/-Br), alcohol (-OH), aldehyde (-CHO), ketone (>C=O), carboxylic (-COOH)).

#### 6. Homologous Series (Pages 9-10, Book pp. 66-67)

- Definition: Compounds with same functional group but differing by -CH₂- unit (e.g., alcohols: CH₃OH, C₂H₅OH, C₃H₇OH).

- Properties: Gradation in physical (mp/bp increase with mass); similar chemical (due to functional group).

- General Formulas: Alkanes (CₙH₂ₙ₊₂), alkenes (CₙH₂ₙ), alkynes (CₙH₂ₙ₋₂).

#### 7. Nomenclature of Carbon Compounds (Pages 10-11, Book pp. 67-68)

- Method: Base name from carbon chain length; add prefix/suffix for functional group (Table 4.4: e.g., -ol for alcohol, -one for ketone, -ene for alkene).

- Examples: Propanol (C₃ alcohol), propanone (C₃ ketone), propene (C₃ alkene).

- Rules: Drop 'e' before vowel-starting suffix; unsaturated chains use -ene/-yne.

- Questions: Structural isomers for pentane; properties leading to many C-compounds; cyclopentane structure.

#### 8. Chemical Properties of Carbon Compounds (Pages 12-14, Book pp. 69-71)

- Combustion: C + O₂ → CO₂ + heat/light. Saturated: clean flame; unsaturated: sooty. Activities: Burn compounds (soot deposition); bunsen burner flames.

- Oxidation: Alcohols to acids using agents like alkaline KMnO₄ or acidified K₂Cr₂O₇ (e.g., ethanol → ethanoic acid).

- Addition: Unsaturated + H₂ (catalyst Ni/Pd) → saturated (hydrogenation of oils).

- Substitution: Saturated + Cl₂ (sunlight) → chlorinated (e.g., CH₄ + Cl₂ → CH₃Cl + HCl).

- Note on Fuels: Coal/petroleum from biomass; fossil fuels produce SOx/NOx pollutants.

- Questions: Ethanol to ethanoic acid as oxidation; ethyne + O₂ for welding (not air).

#### 9. Some Important Carbon Compounds – Ethanol and Ethanoic Acid (Pages 14-17, Book pp. 71-74)

- Ethanol (C₂H₅OH): Liquid (mp 156 K, bp 351 K); solvent in medicines; soluble in water. Reactions: With Na (→ sodium ethoxide + H₂); dehydration (hot conc. H₂SO₄ → ethene). Harmful: Causes drunkenness, death in excess; denatured for industry.

- Ethanoic Acid (CH₃COOH): Acetic acid; 5-8% vinegar; mp 290 K (glacial). Weak acid. Reactions: Esterification (with ethanol → ester + H₂O); with base (→ salt + H₂O); with carbonates (→ salt + CO₂ + H₂O). Activities: pH comparison with HCl; ester formation (sweet smell).

- Alcohol as Fuel: From sugarcane; cleaner additive to petrol.

#### 10. Soaps and Detergents (Pages 17-19, Book pp. 74-76)

- Soaps: Na/K salts of long-chain carboxylic acids. Form micelles (hydrophilic head in water, hydrophobic tail in oil); emulsify dirt.

- Cleaning Mechanism: Micelles trap oil; agitation helps removal. Hard water forms scum (Ca/Mg precipitates).

- Detergents: Effective in hard water (no scum); used in shampoos/clothes cleaners.

- Activities: Oil + water ± soap (emulsion); hard water with soap/detergent (foam/scum).

- Questions: Check hard water with detergent; agitation for cleaning.

#### 11. Summary and Exercises (Pages 20-21, Book pp. 77-78)

- What You Have Learnt: Recap of carbon's versatility, bonding, series, properties, compounds, and soaps.

- Exercises: 15 questions (MCQs, short answers) on bonds, structures, reactions, etc.

- Group Activities: Make models; prepare soap from oil.

This chapter emphasizes carbon's role in organic chemistry, with practical activities (13 total) and diagrams (e.g., structures, micelles). It builds foundational knowledge for hydrocarbons and functional groups, highlighting real-world applications like fuels and cleaning agents. The total content focuses on conceptual understanding over rote memorization.