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Practice Class 9 Science MCQ Questions with Answers based on the latest NCERT syllabus. Learn about intermolecular forces, collenchyma tissue, proton discovery, SI unit of momentum, and velocity 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:
- Matter in Our Surroundings
- Tissues
- Structure of the Atom
- Motion
- Force and Laws of Motion
Question Type: Multiple Choice Questions (MCQs)
Difficulty Level: Easy to Moderate
Based On: Latest NCERT Syllabus
Introduction
Class 9 Science develops a strong understanding of matter, plant tissues, atomic structure, and mechanics. Concepts such as intermolecular forces, collenchyma tissue, protons, momentum, and velocity are essential for understanding both Biology and Physics. This practice set provides original, NCERT-aligned explanations that help students strengthen concepts and prepare confidently for examinations.
What You Will Learn
✔ Intermolecular forces in different states of matter
✔ Functions of collenchyma tissue
✔ Discovery of the proton
✔ SI unit of momentum
✔ Velocity as a vector quantity
Why This Topic Is Important?
These concepts are fundamental to Class 9 Science and are frequently tested in CBSE, State Board, Olympiad, and scholarship examinations. A clear understanding of these topics also supports learning in higher classes.
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. Which state of matter has the weakest intermolecular forces?
A) Solid
B) Liquid
C) All of these
D) Gas
Answer: Gas
Concept
The strength of intermolecular forces determines how closely particles are held together.
Explanation
In the gaseous state, particles are far apart and experience very weak intermolecular forces. As a result, gases have no fixed shape or volume and can move freely in all directions.
Exam Focus
Remember:
Solid → Strongest forces
Liquid → Moderate forces
Gas → Weakest forces
Detailed Explanation:
Matter exists in three main states: solid, liquid, and gas. The particles in each state are held together by intermolecular forces (forces between molecules).
- In solids, particles are tightly packed → strong forces
- In liquids, particles are less tightly packed → moderate forces
- In gases, particles are far apart → very weak forces
Why gases have weakest forces?
In gases, particles move freely in all directions and have maximum distance between them. Because of this, the attraction between particles is very weak.
Examples:
- Air spreads easily in a room
- Gas can be compressed easily
👉 Exam Line:
“Gases have the weakest intermolecular forces because their particles are far apart and move freely.”
Q2. SI unit of momentum is:
A) Joule
B) Watt
C) Newton
D) kg m/s
Answer: kg m/s
Concept
Momentum is the quantity of motion possessed by an object.
Explanation
Momentum is calculated as the product of mass and velocity.
Formula
$$p = mv$$
Where:
- $$p$$ = Momentum
- $$m$$ = Mass
- $$v$$ = Velocity
Therefore, the SI unit of momentum is:
$$\mathrm{kg;m/s}$$
Exam Focus
Remember:
Momentum = Mass × Velocity
SI Unit = kg·m/s
🔍 Detailed Explanation:
Momentum is defined as the product of mass and velocity:
Momentum = Mass × Velocity
- Mass is measured in kilograms (kg)
- Velocity is measured in meters per second (m/s)
So, the SI unit becomes:
kg × m/s = kg m/s
Important Concept:
Momentum is a vector quantity, meaning it has both magnitude and direction.
Examples:
- A fast-moving truck has more momentum than a bicycle
- Increasing speed increases momentum
👉 Exam Line:
“The SI unit of momentum is kg m/s as it is the product of mass and velocity.”
Q3. Proton was discovered by:
A) Rutherford
B) Chadwick
C) Thomson
D) Bohr
Answer: Rutherford
Concept
The proton is a positively charged subatomic particle present in the nucleus of an atom.
Explanation
Ernest Rutherford is credited with the discovery of the proton through his experiments on atomic structure. The proton carries one positive charge and contributes to the atomic number of an element.
Exam Focus
Remember:
- Electron → J. J. Thomson
- Proton → Ernest Rutherford
- Neutron → James Chadwick
Detailed Explanation:
The proton is a positively charged particle present in the nucleus of an atom.
Ernest Rutherford discovered the proton during his experiments on atomic structure. His work helped in understanding the nucleus of the atom.
Key Contributions:
- Discovered the nucleus
- Identified positively charged particles (protons)
Examples:
- Every atom has protons in its nucleus
- The number of protons decides the element
👉 Exam Line:
“Proton was discovered by Ernest Rutherford during atomic structure experiments.”
Q4. Velocity is:
A) Both
B) None
C) Scalar
D) Vector
Answer: Vector
Concept
A vector quantity has both magnitude and direction.
Explanation
Velocity describes how fast an object moves and the direction in which it moves. Since direction is included, velocity is classified as a vector quantity.
Exam Focus
Remember:
- Speed → Scalar
- Velocity → Vector
Detailed Explanation:
Velocity is defined as the speed of an object in a particular direction.
- Speed only tells how fast something moves → scalar
- Velocity tells both speed and direction → vector
Why velocity is a vector?
Because direction is always required to fully describe velocity.
Examples:
- 20 m/s → speed
- 20 m/s north → velocity
👉 Exam Line:
“Velocity is a vector quantity because it has both magnitude and direction.”
Q5. Collenchyma provides:
A) Photosynthesis
B) Transport
C) Flexibility
D) Storage
Answer: Flexibility
Concept
Collenchyma is a living mechanical tissue found mainly in young stems and leaf stalks.
Explanation
Collenchyma provides flexibility and mechanical support to growing parts of the plant. It allows stems and leaves to bend without breaking.
Exam Focus
Remember: Collenchyma = Support + Flexibility
Detailed Explanation:
Collenchyma is a type of plant tissue found in stems and leaves.
Its main function is to provide support along with flexibility, allowing plants to bend without breaking.
Key Features:
- Cells are elongated
- Walls are unevenly thickened
- Found in growing parts of plants
Examples:
- Helps stems bend in wind
- Found in leaf stalks
👉 Exam Line:
“Collenchyma provides flexibility and mechanical support to plants.”
Quick Revision (Fast Recall):
- Gas → weakest forces
- Momentum → kg m/s
- Proton → Rutherford
- Velocity → vector
- Collenchyma → flexibility
Important Formulas & Concepts
1. States of Matter
Solids
- Strong intermolecular forces
- Fixed shape and volume
Liquids
- Moderate intermolecular forces
- Fixed volume but no fixed shape
Gases
- Weakest intermolecular forces
- Neither fixed shape nor fixed volume
2. Collenchyma Tissue
Functions:
- Provides flexibility
- Gives mechanical support
- Present in young stems and leaf stalks
3. Proton
- Positively charged particle
- Present inside the nucleus
- Determines the atomic number
4. Momentum
Formula:
$$p = mv$$
SI Unit:
$$\mathrm{kg;m/s}$$
5. Velocity
Definition:
Velocity is the rate of change of displacement with time.
Formula:
$$v=\frac{\text{Displacement}}{\text{Time}}$$
SI Unit:
$$\mathrm{m/s}$$
Related Practice Questions
- Why are intermolecular forces weakest in gases?
- State two functions of collenchyma tissue.
- Who discovered the proton?
- Write the formula and SI unit of momentum.
- Differentiate between speed and velocity.
Mini Quiz Challenge
True or False
- Gases have the weakest intermolecular forces.
- Collenchyma provides flexibility to plants.
- Rutherford discovered the proton.
- The SI unit of momentum is kg·m/s.
- Velocity is a vector quantity.
Exam Tips
✔ Learn the order of intermolecular force strength in solids, liquids, and gases.
✔ Do not confuse collenchyma with xylem or phloem.
✔ Remember the scientists associated with the discovery of subatomic particles.
✔ Memorize the momentum formula and SI unit.
✔ Always distinguish between speed and velocity.
Quick Revision Notes
✔ Gases have the weakest intermolecular forces.
✔ Collenchyma provides flexibility and support.
✔ Rutherford discovered the proton.
✔ Momentum:
$$p = mv$$
✔ SI Unit of Momentum:
$$\mathrm{kg;m/s}$$
✔ Velocity is a vector quantity.
Common Mistakes Students Make
❌ Thinking liquids have the weakest intermolecular forces.
❌ Confusing collenchyma with parenchyma.
❌ Mixing up the discoveries of electron, proton, and neutron.
❌ Writing Newton as the SI unit of momentum.
❌ Treating velocity as a scalar quantity.
Key Takeaways
- Gases have the weakest intermolecular forces among the three common states of matter.
- Collenchyma tissue provides flexibility and mechanical support to plants.
- Ernest Rutherford is credited with the discovery of the proton.
- Momentum is the product of mass and velocity, and its SI unit is kg·m/s.
- Velocity is a vector quantity because it has both magnitude and direction.
FAQs
1. Which state of matter has the weakest intermolecular forces?
The gaseous state has the weakest intermolecular forces.
2. What is the function of collenchyma tissue?
Collenchyma provides flexibility and mechanical support to growing parts of plants.
3. Who discovered the proton?
The proton was discovered by Ernest Rutherford.
4. What is the SI unit of momentum?
The SI unit of momentum is
$$\mathrm{kg;m/s}$$
5. Is velocity a scalar or vector quantity?
Velocity is a vector quantity because it has both magnitude and direction.
NCERT Reference
Book: NCERT Science Class 9
Chapters Covered:
- Chapter 1 – Matter in Our Surroundings
- Chapter 6 – Tissues
- Chapter 4 – Structure of the Atom
- Chapter 8 – Motion
- Chapter 9 – Force and Laws of Motion
Based On: Latest NCERT Curriculum (CBSE)
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