PW ICSE Class 9 Chemistry Mid-Term 2026: Check Top 20 Questions From PW Marathon
Gunika Shah3 Sept, 2026
Chemistry revision before your mid-term requires more than remembering definitions and chemical formulae. You may know what valency means but still need to use it to write a formula, explain why a reaction is exothermic, or connect an experiment with what it revealed about atomic structure. Practising such questions can show you which concepts are actually clear.
The PW ICSE Class 9 Chemistry Mid-Term Marathon combines concept revision with question practice across different parts of the syllabus. The session covers the language of chemistry, chemical changes and reactions, water, atomic structure and chemical bonding, and the periodic table. The selected questions below can help you revisit these areas before the exam.
Which ICSE Class 9 Chemistry Concepts Are Covered in the PW Mid-Term Marathon 2026?
The PW Chemistry Mid-Term Marathon moves across five Chemistry sections, with explanations, examples, and questions used throughout the session. Instead of revising each topic only through definitions, you can use the marathon to check whether you can apply the concepts while solving questions.
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Chemistry Section |
Key Areas Covered |
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The Language of Chemistry |
Symbols, valency, ions, radicals, variable valency, writing and naming chemical formulae |
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Chemical Changes and Reactions |
Chemical equations, balancing equations, exothermic reactions and endothermic reactions |
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Water |
Composition of water, hardness, water of crystallisation, hydrated and anhydrous salts, efflorescence |
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Atomic Structure and Chemical Bonding |
Structure of an atom, atomic number, mass number, Rutherfordās experiment, electronic configuration and covalent bonding |
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Periodic Table |
Dobereinerās triads, Newlandsā Law of Octaves, Mendeleevās periodic table and periodic classification |
These sections include both recall-based concepts and areas where you need to explain a reason, apply a rule, or connect one Chemistry idea with another.
Top 20 Chemistry Questions for ICSE Class 9 From the PW Mid-Term Marathon 2026
The complete PW Chemistry Mid-Term Marathon includes more questions, examples, and explanations for revision. Try answering each question before checking the answer. If you know the final answer but cannot explain the reasoning behind it, return to that part of the marathon before moving ahead.
The Language of Chemistry
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No. |
Question |
Answer |
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Q1 |
What is valency? How can you calculate the valency of an element from its valence electrons? |
Valency is the combining capacity of an element. It is related to the number of electrons an atom loses, gains, or shares to achieve a stable electronic configuration. For elements with 1 to 4 valence electrons, valency is generally equal to the number of valence electrons. For 5 to 7 valence electrons, valency can be calculated as 8 minus the number of valence electrons. |
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Q2 |
What are ions? Differentiate between a cation and an anion. |
Ions are charged species formed when the number of electrons and protons becomes unequal. A cation is positively charged and is generally formed by the loss of electrons, while an anion is negatively charged and is generally formed by the gain of electrons. |
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Q3 |
What are simple ions and polyatomic ions? Give examples of each. |
A simple ion consists of a single charged atom, such as Naāŗ or Clā». A polyatomic ion consists of a group of atoms carrying a charge and behaving as a single unit, such as NHāāŗ or SOāĀ²ā». |
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Q4 |
What is variable valency? Why do elements such as iron and copper show variable valency? |
Variable valency means that an element can show more than one valency in different compounds. Iron can form FeĀ²āŗ and FeĀ³āŗ ions, while copper can form Cuāŗ and CuĀ²āŗ ions. This occurs because electrons may be lost from the valence shell and, in some cases, from the penultimate shell. |
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Q5 |
Write the chemical formulae of ammonium sulphate, calcium hydroxide, and aluminium sulphate using their valencies. |
Ammonium sulphate: (NHā)āSOāCalcium hydroxide: Ca(OH)āAluminium sulphate: Alā(SOā)ā |
Chemical Changes and Reactions
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No. |
Question |
Answer |
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Q6 |
Why is it necessary to balance a chemical equation? |
A chemical equation is balanced so that the number of atoms of each element is the same on the reactant and product sides. This follows the principle that atoms are neither created nor destroyed during a chemical reaction. |
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Q7 |
Differentiate between an exothermic reaction and an endothermic reaction. |
An exothermic reaction releases heat to the surroundings, while an endothermic reaction absorbs heat from the surroundings. |
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Q8 |
What happens to the temperature during an exothermic reaction? Explain why. |
The temperature generally increases during an exothermic reaction because heat energy is released into the surroundings. |
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Q9 |
What indications can help you identify that a chemical reaction has taken place? |
A chemical reaction may be indicated by the formation of a new substance, a change in colour, evolution of a gas, formation of a precipitate, or change in temperature. |
Water
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No. |
Question |
Answer |
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Q10 |
In what volume ratio do hydrogen and oxygen combine to form water? What is their mass ratio? |
Hydrogen and oxygen combine in the volume ratio of 2:1 to form water. Their mass ratio is 1:8. |
|
Q11 |
What is hardness of water? Which compounds of calcium and magnesium are responsible for it? |
Hardness of water is caused by the presence of certain dissolved salts of calcium and magnesium. Bicarbonates, chlorides, and sulphates of calcium and magnesium can contribute to hardness. |
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Q12 |
Explain how calcium and magnesium bicarbonates can cause hardness of water. |
When water flows over rocks such as limestone and dolomite, compounds containing calcium and magnesium can form soluble bicarbonates. These dissolve in water and contribute to its hardness. |
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Q13 |
What is water of crystallisation? Differentiate between hydrated and anhydrous salts. |
Water of crystallisation is the fixed number of water molecules chemically associated with a crystalline salt. A hydrated salt contains water of crystallisation, while an anhydrous salt does not contain this water. |
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Q14 |
What is efflorescence? How does dry or humid weather affect efflorescence? |
Efflorescence is the loss of water of crystallisation from a hydrated salt when it is exposed to air. It occurs more rapidly in dry weather and more slowly under humid conditions. |
Atomic Structure and Chemical Bonding
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No. |
Question |
Answer |
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Q15 |
What is an atom? Why are atoms called the building blocks of matter? |
An atom is the smallest particle of an element that exhibits the properties of that element. Atoms are called the building blocks of matter because substances are made up of atoms. |
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Q16 |
What is the relationship between mass number, atomic number, and number of neutrons? |
The mass number is equal to the total number of protons and neutrons in the nucleus. Mass number = Atomic number + Number of neutrons. Therefore, Number of neutrons = Mass number ā Atomic number. |
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Q17 |
What did Rutherfordās alpha-particle scattering experiment establish about atomic structure? |
Rutherfordās experiment showed that an atom contains a very small, dense, positively charged region called the nucleus. It also helped establish that much of the atom consists of empty space. |
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Q18 |
What is a covalent bond? How is it formed? |
A covalent bond is formed when atoms share electrons with one another. Sharing allows the atoms to move towards a stable electronic configuration. |
Periodic Table
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No. |
Question |
Answer |
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Q19 |
State Newlandsā Law of Octaves. What observation led Newlands to propose it? |
Newlands arranged the known elements in increasing order of their atomic masses and observed that the properties of every eighth element were similar to those of the first. This repeating pattern was called Newlandsā Law of Octaves. |
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Q20 |
What were the major limitations of Mendeleevās periodic table, particularly regarding isotopes and hydrogen? |
Mendeleevās periodic table could not provide separate positions for isotopes because they have different atomic masses but similar chemical properties. It also could not give hydrogen a definite position because hydrogen shows similarities with more than one group of elements. |
The questions above cover selected areas discussed during the marathon, but they are not the complete question practice available in the session. You can return to the PW Chemistry Mid-Term Marathon for additional examples, questions, and explanations when a particular section needs more revision.
Which Chemistry Concepts Need More Attention Before the Mid-Term?
Once you finish the questions, look at the ones where you needed help recalling a rule, writing a formula, or explaining the reason behind an answer. These are some of the areas worth practising again:
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Valency and ions: Check whether you can determine valency from valence electrons and distinguish cations from anions.
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Writing chemical formulae: Practise using valencies correctly, especially when brackets and polyatomic ions are involved.
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Variable valency: Keep common examples such as iron and copper clear and distinguish their different ionic forms.
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Chemical equations: Make sure you understand why equations are balanced instead of only memorising the balancing steps.
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Exothermic and endothermic reactions: Connect heat transfer with the change observed in the surroundings.
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Hardness of water: Revise the calcium and magnesium compounds responsible for hardness and how they enter water.
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Water of crystallisation: Keep hydrated salts, anhydrous salts, and efflorescence separate.
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Atomic structure: Practise connecting atomic number, mass number, protons, and neutrons.
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Chemical bonding: Focus on what happens to electrons during bond formation.
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Periodic classification: Keep the basis, observations, and limitations of the early periodic classifications clear.
A useful way to check your revision is to see whether you can explain why an answer is correct without looking at your notes. If you remember the term or formula but cannot explain the concept behind it, give that section another round of revision before the exam.
How Can the PW ICSE Class 9 Chemistry Mid-Term Marathon Strengthen Your Revision?
The PW Chemistry Mid-Term Marathon brings several Chemistry sections into one revision session so that you can move between concept recall and question practice. You can use the marathon more actively by stopping at questions, checking your own answers, and returning only to the explanations that you need to strengthen.
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Attempt the Question Before the Explanation
When a question appears during the marathon, pause and solve it yourself. This helps you check whether you can recall the concept independently instead of recognising the answer only after it is explained.
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Return to the Concept Behind a Mistake
If you answer incorrectly, identify what caused the mistake. You may need to revise a valency rule, the meaning of a term, an atomic concept, or a periodic classification rather than revisiting the complete section.
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Practise Formula Writing Separately
Formula-based questions require you to apply valencies correctly. Practise examples involving simple ions as well as polyatomic ions so that you become comfortable with the use of subscripts and brackets.
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Give Reasoning Questions Enough Attention
Topics such as exothermic reactions, hardness of water, Rutherfordās experiment, variable valency, and periodic classification require more than one-word answers. Use the marathon explanations to understand the reason behind each concept.
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Reattempt Questions Without Notes
After revising all five sections, return to the questions and attempt them without your notes. Questions you can now answer independently show where your revision has improved, while repeated mistakes tell you exactly what to revise again.
The PW ICSE Class 9 Chemistry Mid-Term Marathon can support your final revision by bringing important concepts and question practice together. Use the selected questions above to identify your stronger and weaker areas, then return to the relevant marathon sections for concepts that still need more practice before the mid-term.
FAQs
1. What should you revise for ICSE Class 9 Chemistry Mid-Term 2026?
2. How should you use the important Chemistry questions from the PW Marathon?
3. Which Chemistry topics need more application-based practice?
4. Does the PW Chemistry Mid-Term Marathon contain more questions than those listed here?
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