ICSE Class 10 Chemistry Mid-Term 2026: Important Questions, Concepts & Must-Practise Topics

ICSE Class 10 Chemistry Mid-Term 2026 preparation is not just about memorising reactions and definitions. You also need to identify ions from observations, draw electron-dot structures, understand periodic trends, write balanced equations and explain chemical behaviour in exam-style questions. With different concepts and question formats to revise, knowing what to focus on can make Chemistry revision more effective.

To bridge these gaps, PW is providing the ICSE Class 10 Chemistry Mid-Term Marathon 2026, covering Analytical Chemistry, Chemical Bonding, Periodic Properties and Variation of Properties, and Acids, Bases and Salts. The marathon combines concept explanations with PYQs, specimen-paper questions, competency-focused questions and different mark-based questions to help you revise concepts and practise their application before the exam.

Important Concepts for ICSE Class 10 Chemistry Mid-Term

The following concepts from the PW Mid-Term Marathon are important for your revision. Focus on the observations, definitions, trends, reactions, and reasons associated with each topic.

Analytical Chemistry

Analytical Chemistry focuses on identifying unknown substances through suitable reagents and observations. Important points include:

• Addition of NaOH or NH₄OH dropwise and then in excess to a metal salt solution.

• Identification of cations through the colour and solubility of precipitates.

• Ca²⁺: White precipitate with NaOH; no visible reaction with NH₄OH.

• Fe²⁺: Dirty or pale green precipitate, insoluble in excess reagent.

• Fe³⁺: Reddish-brown precipitate, insoluble in excess reagent.

• Cu²⁺: Pale blue precipitate; dissolves in excess NH₄OH to form a deep inky-blue solution.

• Zn²⁺: White gelatinous precipitate; dissolves in excess NaOH and NH₄OH.

• Pb²⁺: Chalky white precipitate; dissolves in excess NaOH but remains insoluble in excess NH₄OH.

• Difference between basic and amphoteric oxides/hydroxides.

Chemical Bonding

Revise how atoms combine through different types of chemical bonds.

• Ionic or electrovalent bond: Formed through the transfer of electrons.

• Covalent bond: Formed through the sharing of electrons.

• Coordinate or dative bond: The shared pair is contributed by only one atom.

• Electron-dot structures of CaO, NaCl, MgCl₂, CH₄, and NH₃.

• Difference between shared pairs and lone pairs.

• Polar and non-polar covalent compounds.

• Formation of NH₄⁺ through a coordinate bond.

• Formation of H₃O⁺ through the donation of a lone pair by oxygen.

Periodic Properties and Variation of Properties

The modern periodic table contains 18 groups and 7 periods. Important areas to revise include:

• Names of important groups, including alkali metals, alkaline earth metals, halogens, and noble gases.

• Position of hydrogen in the periodic table.

• Finding the group and period of an element from its electronic configuration.

• Variation of atomic radius across a period and down a group.

• Variation of metallic and non-metallic character.

• Trends in ionisation energy, electron affinity, and electronegativity.

• Reasons behind periodic trends and important exceptions.

Acids, Bases and Salts

Revise the properties, classification, reactions, and preparation methods related to acids, bases, and salts.

• Natural indicators such as litmus and turmeric.

• Synthetic indicators such as phenolphthalein and methyl orange.

• Olfactory indicators.

• Hydracids and oxyacids.

• Classification of acids as mono-, di-, and tribasic.

• Classification of bases according to their acidity.

• Reactions of acids with metals, carbonates, bicarbonates, and sulphides.

• Tests for hydrogen and carbon dioxide.

• Classification of oxides as basic, acidic, amphoteric, and neutral.

• pH scale from 0 to 14 and the role of universal indicator.

• Salt preparation through displacement, neutralisation, and precipitation reactions.

ICSE Class 10 Chemistry: 3, 5 & 7-Mark Important Questions

Practising different mark-based questions can help you become familiar with the level of explanation required in the exam. Here are some important questions based on the concepts covered in the PW marathon.

Most Important 3-Marker Questions

1. Why is NaOH or NH₄OH added dropwise and then in excess to a metal salt solution?

Adding the reagent dropwise allows the precipitate to form gradually so that its colour and appearance can be observed. When the reagent is added in excess, the behaviour of the precipitate can be checked. If it dissolves or remains insoluble, this provides further evidence for identifying the cation.

2. A metal salt solution gives a white precipitate with NaOH but no visible reaction with NH₄OH. Identify the cation and give a reason.

The cation is Ca²⁺. NaOH is a strong base and provides sufficient OH⁻ ions to form a white precipitate of calcium hydroxide. NH₄OH is a weak base and does not provide enough OH⁻ ions to produce a visible precipitate of Ca(OH)₂.

3. How can you test for hydrogen and carbon dioxide gases?

• Hydrogen: A burning splint brought near the gas produces a characteristic squeaky pop.

• Carbon dioxide: Passing the gas through limewater turns it milky due to the formation of calcium carbonate.

4. Classify HCl and H₂SO₄ as hydracids or oxyacids and state their basicity.

• HCl: Hydracid and monobasic.

• H₂SO₄: Oxyacid and dibasic.

5. Explain the formation of calcium oxide using an electron-dot structure.

Calcium loses two electrons to form Ca²⁺, while oxygen gains two electrons to form O²⁻. The electrostatic attraction between the oppositely charged ions results in the formation of an ionic bond in CaO.

Most Important 5-Marker Questions

1. How can ZnSO₄ and CuSO₄ solutions be distinguished using NH₄OH?

With CuSO₄, adding NH₄OH gives a pale blue precipitate of Cu(OH)₂. The precipitate dissolves in excess NH₄OH to produce a deep inky-blue solution.

CuSO₄ + 2NH₄OH → Cu(OH)₂↓ + (NH₄)₂SO₄

With ZnSO₄, adding NH₄OH produces a white gelatinous precipitate of Zn(OH)₂. This dissolves in excess NH₄OH to give a colourless solution.

ZnSO₄ + 2NH₄OH → Zn(OH)₂↓ + (NH₄)₂SO₄

Therefore, the deep blue solution confirms Cu²⁺, while the colourless solution after dissolution indicates Zn²⁺.

2. Explain the formation of the ammonium ion (NH₄⁺).

In NH₃, nitrogen has one lone pair of electrons. An H⁺ ion has no electrons and can accept an electron pair. Nitrogen donates its lone pair to H⁺, forming a coordinate bond.

NH₃ + H⁺ → NH₄⁺

The resulting ion has an overall +1 charge because it contains one more proton than electron.

3. What is the pH scale? Explain the meaning of pH values 7, below 7, and above 7.

The pH scale indicates the acidic or basic nature of a solution and generally ranges from 0 to 14 at 25°C.

• pH = 7: Neutral solution.

• pH < 7: Acidic solution.

• pH > 7: Basic or alkaline solution.

A universal indicator contains a mixture of indicators and shows different colours at different pH values. Unlike litmus, it can give an approximate indication of the strength of an acid or base.

4. Explain how the hydronium ion (H₃O⁺) is formed.

Water undergoes self-ionisation:

2H₂O ⇌ H₃O⁺ + OH⁻

One water molecule provides H⁺, while another water molecule accepts the proton using a lone pair of electrons on oxygen. A coordinate bond is formed between oxygen and hydrogen, producing the hydronium ion, H₃O⁺.

5. Distinguish between ionic and covalent compounds.

Most Important 7-Marker Questions

1. Explain the difference between basic and amphoteric oxides or hydroxides with examples. Write equations for Al(OH)₃ reacting with an acid and a base.

Basic oxides and hydroxides generally react with acids to form salt and water. Examples include Na₂O, NaOH, CaO, Ca(OH)₂, MgO, and CuO.

Amphoteric oxides and hydroxides can react with both acids and bases. Examples include Al₂O₃, Al(OH)₃, ZnO, Zn(OH)₂, PbO, and Pb(OH)₂.

Al(OH)₃ reacts with hydrochloric acid:

Al(OH)₃ + 3HCl → AlCl₃ + 3H₂O

It also reacts with sodium hydroxide:

Al(OH)₃ + NaOH → NaAlO₂ + 2H₂O

Thus, Al(OH)₃ shows both acidic and basic behaviour.

2. Explain the variation of atomic radius, ionisation energy, and electronegativity across Period 3 and down Group 1.

Across Period 3, the number of electron shells remains the same while nuclear charge increases. The stronger attraction between the nucleus and electrons causes:

• Atomic radius to decrease.

• Ionisation energy to generally increase.

• Electronegativity to increase.

Down Group 1, an additional electron shell is added at each step. The outer electron becomes farther from the nucleus, resulting in:

• Atomic radius increasing.

• Ionisation energy decreasing.

• Electronegativity decreasing.

Metallic character increases down Group 1 because the outer electron can be removed more easily.

3. Describe suitable methods for preparing zinc chloride, potassium nitrate, and calcium carbonate.

(a) Zinc chloride — displacement:

Zn + 2HCl → ZnCl₂ + H₂↑

(b) Potassium nitrate — neutralisation:

KOH + HNO₃ → KNO₃ + H₂O

(c) Calcium carbonate — precipitation:

CaCl₂ + Na₂CO₃ → CaCO₃↓ + 2NaCl

The method used depends on the nature of the salt and the reactants available.

4. Explain the formation of NH₄⁺ and H₃O⁺ through coordinate bonding.

In NH₄⁺, nitrogen in NH₃ has a lone pair that it donates to H⁺, forming a coordinate bond:

NH₃ + H⁺ → NH₄⁺

In H₃O⁺, oxygen in H₂O donates a lone pair to H⁺:

H₂O + H⁺ → H₃O⁺

In both cases, the incoming H⁺ contributes a proton but no electron. Therefore, the resulting ions carry an overall +1 charge.

5. Complete the table showing the observations obtained when NaOH and NH₄OH are added to different metal cations.

These observations are useful for identifying the metal cation present in an unknown salt solution.

Note: For more important questions and a deeper understanding of the concepts covered here, watch the PW Class 10 Mid-Term Marathon and revise along with the explanations.

How Does the PW Marathon Help With ICSE Class 10 Chemistry Revision?

The marathon brings important concepts and question practice together so that you can revise the topics covered in the session without limiting your preparation to definitions alone.

• Concept revision: Important Chemistry concepts are explained before moving to related questions.

• Previous-year questions: PYQs help you understand the types of questions that have appeared in examinations.

• Specimen-paper practice: Questions from specimen papers provide exposure to exam-style formats.

• Competency-focused questions: These help you practise applying concepts instead of only recalling facts.

• Different mark-based questions: The session includes questions requiring short answers as well as detailed explanations.

Using these questions along with your textbook and class notes can help you identify topics that need more practice before the mid-term exam.