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Practice Class 9 Science MCQ Questions with Answers based on the latest NCERT syllabus. Learn about atomic number, work, sublimation, xylem, and speed with original concept-based explanations, exam-focused notes, and NCERT-aligned content for CBSE and State Board students.
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Chapter Information
Subject: Science
Class: 9
Chapters Covered:
- Structure of the Atom
- Force and Laws of Motion
- Matter in Our Surroundings
- The Fundamental Unit of Life
- Motion
Question Type: Multiple Choice Questions (MCQs)
Difficulty Level: Easy to Moderate
Based On: Latest NCERT Syllabus
Introduction
Class 9 Science introduces students to important concepts from Physics, Chemistry, and Biology. Topics such as atomic structure, work, sublimation, plant transport systems, and motion are fundamental for understanding advanced scientific principles. This practice set provides original, concept-based explanations to strengthen understanding and improve exam performance.
What You Will Learn
✔ Atomic number
✔ Conditions for zero work
✔ Sublimation
✔ Function of xylem
✔ Scalar quantity (Speed)
Why This Topic Is Important?
These concepts are essential for building a strong scientific foundation and are frequently asked in CBSE, State Board, Olympiad, and scholarship examinations. Understanding the underlying concepts helps students solve both objective and descriptive questions confidently.
Exam Relevance
These questions are useful for:
✔ CBSE Exams
✔ State Board Exams
✔ School Tests
✔ Unit Tests
✔ Half-Yearly Exams
✔ Annual Exams
✔ Olympiad Preparation
✔ Scholarship Examinations
Q1. Sublimation example:
A) Camphor
B) Milk
C) Water
D) Ice
Answer
Camphor
Concept
Sublimation is the direct change of a solid into a gas without passing through the liquid state.
Explanation
Camphor is a common substance that undergoes sublimation. On heating, it changes directly from a solid into vapour without becoming a liquid. Other examples include naphthalene balls and ammonium chloride.
Exam Focus
Remember: Camphor, naphthalene, and ammonium chloride show sublimation.
explanation:
- Sublimation is a process where a solid changes directly into gas without becoming liquid.
- Some substances have this special property.
- Camphor (kapoor) when heated, directly turns into vapour.
- Ice and water first melt into liquid before becoming gas.
Conclusion:
Camphor is an example of sublimation.
Q2. Work done is zero when:
A) Motion occurs
B) Distance is zero
C) Force is applied
D) Speed increases
Answer
Distance is zero
Concept
Work is done only when a force causes displacement in the direction of the force.
Explanation
If there is no displacement (distance = 0), the work done is zero, even if a force is applied. For example, pushing a wall that does not move results in zero work because there is no displacement.
Formula
$$W = F \times s$$
Where:
- $$W$$ = Work
- $$F$$ = Force
- $$s$$ = Displacement
If $$s=0$$,
$$W=0$$
Exam Focus
Remember: No displacement ⇒ No work done.
explanation:
- Work is defined as:
👉 Work = Force × Distance - If distance = 0, then:
👉 Work = Force × 0 = 0 - Even if force is applied, without movement, no work is done.
- Example: pushing a wall that does not move.
Conclusion:
Work done is zero when distance is zero.
Q3. Atomic number represents:
A) Protons
B) Neutrons
C) Mass
D) Electrons + Neutrons
Answer
Protons
Concept
The atomic number identifies an element by the number of protons present in its nucleus.
Explanation
The atomic number (Z) is equal to the number of protons in the nucleus of an atom. Since every element has a unique number of protons, the atomic number determines the identity of the element. In a neutral atom, the number of electrons is also equal to the number of protons.
Exam Focus
Remember: Atomic Number = Number of Protons
explanation:
- Every atom has protons, neutrons, and electrons.
- The Atomic number tells us the number of protons in the nucleus.
- In a neutral atom:
👉 Number of protons = number of electrons - Atomic number helps identify the element.
Conclusion:
Atomic number represents number of protons.
Q4. Speed is:
A) Vector
B) Scalar
C) None
D) Both
Answer
Scalar
Concept
Physical quantities are classified as scalar or vector depending on whether they include direction.
Explanation
Speed is a scalar quantity because it has only magnitude and does not include direction. In contrast, velocity is a vector quantity because it has both magnitude and direction.
Exam Focus
Remember:
- Speed → Scalar
- Velocity → Vector
explanation:
- Physical quantities are of two types:
- Scalar → only magnitude (value)
- Vector → magnitude + direction
- Speed tells how fast something moves.
- It does not include direction.
- Velocity includes direction, but speed does not.
Conclusion:
Speed is a scalar quantity.
Q5. Xylem transports
A) Food
B) Oxygen
C) Water
D) Hormones
Answer
Water
Concept
Plants have specialized tissues for transporting different materials.
Explanation
Xylem transports water and dissolved minerals from the roots to the stem, leaves, and other parts of the plant. This transport is essential for photosynthesis, growth, and maintaining plant structure.
Exam Focus
Remember:
- Xylem → Water and minerals
- Phloem → Food
explanation:
- Plants have special tissues for transport.
- Xylem carries water and minerals.
- It transports water from roots to leaves.
- Food is transported by another tissue called phloem.
Conclusion:
Xylem transports water.
Important Formulas & Concepts
1. Atomic Number
- Symbol: Z
- Represents the number of protons in an atom.
- Determines the identity of an element.
2. Work
Formula:
$$W = F \times s$$
SI Unit:
Joule (J)
Special Case:
If
$$s = 0$$
Then
$$W = 0$$
3. Sublimation
Definition:
Direct conversion of a solid into vapour without passing through the liquid state.
Examples:
- Camphor
- Naphthalene
- Ammonium chloride
4. Xylem
Functions:
- Transports water.
- Transports dissolved minerals.
- Provides mechanical support.
5. Scalar and Vector Quantities
Scalar
- Speed
- Mass
- Distance
- Time
- Temperature
Vector
- Velocity
- Force
- Displacement
- Acceleration
Related Practice Questions
- Define atomic number.
- Under what condition is work equal to zero?
- What is sublimation? Give two examples.
- Differentiate between xylem and phloem.
- Explain the difference between speed and velocity.
Mini Quiz Challenge
True or False
- Atomic number equals the number of protons.
- Work is done even if displacement is zero.
- Camphor undergoes sublimation.
- Xylem transports food.
- Speed is a scalar quantity.
Exam Tips
✔ Do not confuse atomic number with mass number.
✔ Remember that work requires displacement.
✔ Learn common examples of sublimation.
✔ Revise the functions of xylem and phloem.
✔ Practice distinguishing scalar and vector quantities.
Quick Revision Notes
✔ Atomic number = Number of protons.
✔ Work is zero when displacement is zero.
✔ Camphor is a common example of sublimation.
✔ Xylem transports water and minerals.
✔ Speed is a scalar quantity.
Common Mistakes Students Make
❌ Confusing atomic number with mass number.
❌ Assuming force alone can produce work.
❌ Thinking ice is an example of sublimation under normal conditions.
❌ Confusing xylem with phloem.
❌ Treating speed as a vector quantity.
Key Takeaways
- Atomic number represents the number of protons in an atom.
- Work is zero when there is no displacement.
- Camphor is a common substance that undergoes sublimation.
- Xylem transports water and dissolved minerals in plants.
- Speed is a scalar quantity because it has magnitude only.
FAQs
1. What does the atomic number represent?
The atomic number represents the number of protons present in the nucleus of an atom.
2. When is work done equal to zero?
Work done is zero when there is no displacement, even if a force is applied.
3. What is sublimation?
Sublimation is the process in which a solid changes directly into vapour without becoming a liquid.
4. What is the function of xylem?
Xylem transports water and dissolved minerals from the roots to other parts of the plant.
5. Is speed a scalar or vector quantity?
Speed is a scalar quantity because it has only magnitude and no direction.
NCERT Reference
Book: NCERT Science Class 9
Chapters Covered:
- Chapter 4 – Structure of the Atom
- Chapter 9 – Force and Laws of Motion
- Chapter 1 – Matter in Our Surroundings
- Chapter 5 – The Fundamental Unit of Life
- Chapter 8 – Motion
Based On: Latest NCERT Curriculum (CBSE)
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