Half Yearly Class 9 Science Set 2 (Solutions)

Time: 3 Hours
Maximum Marks: 80
General Instructions:
(i) The question paper comprises four sections: A, B, C, and D. 
(ii) All questions are compulsory. However, internal choices are provided in some questions. 
(iii) Section A consists of 20 objective type questions (MCQs/Assertion-Reason) carrying 1 mark each. 
(iv) Section B consists of 7 very short answer questions carrying 2 marks each. 
(v) Section C consists of 7 short answer questions carrying 3 marks each. 
(vi) Section D consists of 5 long answer questions carrying 5 marks each. 
(vii) Draw neat and labelled diagrams wherever necessary

Syllabus: The half-yearly question paper is framed from the following chapters: Matter in our surroundings, Is matter around us  pure?, Fundamental unit of life, tissues, Motion, Forces and laws of Motion.

Section A

Q1. The temperature at which a liquid starts boiling is called:   (1 Mark)
(a) Melting point 
(b) Boiling point
(c) Freezing point 
(d) Sublimation point 

Ans: (b)
Sol: The boiling point is the temperature at which a liquid changes to a gas throughout its volume.

Q2. Which of the following is a pure substance?   (1 Mark)
(a) Air 
(b) Sugar syrup 
(c) Sodium chloride 
(d) Milk 

Ans: (c)
Sol: Sodium chloride is a pure substance (compound) with a fixed composition.

Q3. The organelle responsible for protein synthesis in a cell is:   (1 Mark)
(a) Ribosome 
(b) Lysosome 
(c) Golgi apparatus 
(d) Endoplasmic reticulum 

Ans: (a)
Sol: Ribosomes are responsible for protein synthesis in the cell.

Q4. Which animal tissue is responsible for movement?   (1 Mark)
(a) Epithelial 
(b) Connective
(c) Muscular 
(d) Nervous 

Ans: (c)
Sol: Muscular tissue is responsible for movement in animals.

Q5. The rate of change of velocity is called:   (1 Mark)
(a) Speed 
(b) Acceleration 
(c) Distance 
(d) Momentum 

Ans: (b)
Sol: Acceleration is the rate of change of velocity.

Q6. The property of an object to resist a change in its state of motion is called:   (1 Mark)
(a) Force 
(b) Inertia 
(c) Friction 
(d) Impulse 

Ans: (b)
Sol: Inertia is the property of an object to resist changes in its state of motion.

Q7. A true solution will:   (1 Mark)
(a) Scatter light 
(b) Settle down over time 
(c) Not scatter light 
(d) Be opaque 

Ans: (c)
Sol: A true solution does not scatter light as its particles are too small.

Q8. The function of lysosomes in a cell is to:   (1 Mark)
(a) Store genetic material 
(b) Digest waste materials 
(c) Produce energy 
(d) Transport proteins 

Ans: (b)
Sol: Lysosomes digest waste materials and worn-out cell parts.

Q9. Which of the following depends on direction?   (1 Mark)
(a) Speed
(b) Distance 
(c) Velocity 
(d) Time 

Ans: (c)
Sol: Velocity depends on direction, unlike speed, which is directionless.

Q10. The momentum of an object is the product of its:   (1 Mark)
(a) Mass and acceleration 
(b) Mass and velocity 
(c) Force and time 
(d) Force and distance

Ans: (b)
Sol: Momentum is the product of an object's mass and velocity.

Q11. Assertion (A): The particles of a gas have maximum kinetic energy.   (1 Mark)
Reason (R): Gas particles move freely in all directions with high speed. 
(a) Both A and R are true, and R is the correct explanation of A. 
(b) Both A and R are true, but R is not the correct explanation of A. 
(c) A is true, but R is false. 
(d) A is false, but R is true. 

Ans: (a)
Sol: Gas particles have maximum kinetic energy due to their free and rapid movement.

Q12. Assertion (A): A suspension is a heterogeneous mixture.   (1 Mark)
Reason (R): The particles of a suspension can be seen with the naked eye. 
(a) Both A and R are true, and R is the correct explanation of A. 
(b) Both A and R are true, but R is not the correct explanation of A. 
(c) A is true, but R is false. 
(d) A is false, but R is true. 

Ans: (b)
Sol: A suspension is heterogeneous, and its particles are visible, but visibility is a prop- erty, not the reason for heterogeneity.

Q13. Assertion (A): The endoplasmic reticulum is involved in protein synthesis.   (1 Mark)
Reason (R): Rough endoplasmic reticulum has ribosomes attached to its surface. 
(a) Both A and R are true, and R is the correct explanation of A. 
(b) Both A and R are true, but R is not the correct explanation of A. 
(c) A is true, but R is false. 
(d) A is false, but R is true. 

Ans: (a)
Sol: Rough endoplasmic reticulum, with ribosomes, is involved in protein synthesis.

Q14. Assertion (A): Cartilage is a connective tissue.   (1 Mark)
Reason (R): It provides support and flexibility to body parts. 
(a) Both A and R are true, and R is the correct explanation of A. 
(b) Both A and R are true, but R is not the correct explanation of A. 
(c) A is true, but R is false. 
(d) A is false, but R is true. 

Ans: (a)
Sol: Cartilage is a connective tissue that supports and provides flexibility to body parts.

Q15. Assertion (A): A body moving in a circular path with constant speed has accel- eration.   (1 Mark)
Reason (R): The direction of velocity changes continuously in circular motion. 
(a) Both A and R are true, and R is the correct explanation of A. 
(b) Both A and R are true, but R is not the correct explanation of A. 
(c) A is true, but R is false. 
(d) A is false, but R is true.

Ans: (a)
Sol: A body in circular motion has acceleration due to continuous change in velocity direction.

Q16. Assertion (A): Momentum is conserved in an isolated system.   (1 Mark)
Reason (R): No external force acts on an isolated system. 
(a) Both A and R are true, and R is the correct explanation of A. 
(b) Both A and R are true, but R is not the correct explanation of A. 
(c) A is true, but R is false. 
(d) A is false, but R is true. 

Ans: (a)
Sol: Momentum is conserved in an isolated system because no external force acts on it.

Q17. Which of the following is not a characteristic of a compound?   (1 Mark)
(a) Fixed composition 
(b) Chemically combined 
(c) Variable composition 
(d) Definite properties 

Ans: (c)
Sol: A compound has a fixed composition, unlike a mixture.

Q18. Which cell organelle contains powerful digestive enzymes and is known as the 'suicide bag' of a cell? (1 Mark)
(a) Lysosome 
(b) Nucleus 
(c) Vacuole 
(d) Chloroplast 

Ans: (a)
Sol: Lysosomes are also known as the 'suicide bags' of a cell because they contain powerful digestive enzymes capable of breaking down organic material, and if the cell gets damaged, they may burst and digest their own cell.

Q19. An object moves with a uniform acceleration of 3 m/s² for 6 seconds, starting from rest. The final velocity is:   (1 Mark)
(a) 12 m/s 
(b) 15 m/s 
(c) 18 m/s 
(d) 21 m/s 

Ans: (c)
Sol: Final velocity: v = u + at = 0 + 3 × 6 = 18 m/s.

Q20. The method used to separate two miscible liquids with different boiling points is:   (1 Mark)
(a) Filtration 
(b) Distillation 
(c) Centrifugation 
(d) Evaporation

Ans: (b)
Sol: Distillation separates miscible liquids based on different boiling points.

Section B

Q1. Define diffusion with an example.  (2 Marks) 

Ans: Diffusion: The movement of particles from a region of higher concentration to a region of lower concentration. Example: Spreading of perfume in a room.

Q2.  What is a homogeneous mixture? Give one example.  (2 Marks) 

Ans: Homogeneous mixture: A mixture with uniform composition throughout.  Ex- ample: Sugar solution in water.

Q3. Name two types of epithelial tissues.  (2 Marks) 

Ans: Two types of epithelial tissues: Squamous epithelium, Cuboidal epithelium.

Q4.  What is the role of phloem in plants?  (2 Marks) 

Ans: Role of phloem: Phloem transports food materials (sugars) from leaves to other parts of the plant.

Q5. Define displacement with an example.  (2 Marks) 

Ans: Displacement: The shortest distance between the initial and final positions of an object. Example: A car moving 5 km north from point A to B has a displacement of 5 km north.

Q6.  State the law of conservation of momentum.  (2 Marks) 

Ans: The Law of Conservation of Momentum states that the total momentum of an isolated system remains constant if no external force acts on it.This is further supported by the assertion that momentum is conserved in an isolated system because no external force acts on it

Q7. Arrange solids, liquids, and gases in increasing order based on the space between their particles, and briefly state why.  (2 Marks) 

Ans:  Increasing Order of Space Between Particles : Solid < Liquid< Gas
Justification: The spaces in between the constituent particles are minimum in the case of solids, intermediate in liquids, and maximum in gases. This variation exists because the strength of the forces of attraction between particles varies from one kind of matter to another. The forces of attraction are maximum in solids, which keeps the particles very close, and minimum in gases, allowing for the maximum space

Section C

Q1. Explain the process of osmosis. Give one example of the importance of osmosis in the life of a plant cell. (3 Marks)

Ans: Osmosis is the movement of water molecules through a selectively permeable membrane. It is a special case of diffusion, defined as the net diffusion of water across this selectively permeable membrane toward a higher solute concentration. Water molecules are free to pass across the membrane in both directions, but the net movement is governed by the concentration difference.

Example of Importance in Plant Cell Life: Absorption of water by plant roots is an example of osmosis. Furthermore, in plant cells, osmosis helps maintain cell structure: when a plant cell gains water through osmosis (e.g., in a hypotonic solution), the vacuole fills up with cell sap and provides turgidity and rigidity to the cell

Q2.  Describe the process of separating a mixture of iron filings and sulphur powder.  (3 Marks) 

Ans:  The mixture of iron filings and sulphur powder is a heterogeneous mixture. Since it is a mixture, the components retain their individual properties, allowing them to be separated easily by physical methods.

1. Principle: The separation utilizes the magnetic property of iron filings.

2. Application (Separation of Iron): A magnet is brought near the mixture. The iron filings, which are attracted towards the magnet, are selectively pulled out and separated from the rest of the material.

3. Collection (Separation of Sulphur): After the iron filings are removed by the magnet, the remaining component, the sulphur powder, is collected separately.

Q3. Draw a labelled diagram of an animal cell.  (3 Marks) 

Ans: 

Q4. Differentiate between parenchyma and collenchyma tissues in plants.  (3 Marks) 

Ans: 

Q5. Derive the first equation of motion: v = u + at.  (3 Marks) 

Ans: This equation relates velocity and time for an object moving with uniform acceleration.

1. Define Acceleration: Acceleration (a) is defined as the measure of the change in the velocity of an object per unit time.

2. Define Variables: Let the initial velocity of the object be u. Let the final velocity of the object be v. Let the time taken for this change be t.

3. Formulate the Equation: The acceleration a is the change in velocity (v-u) divided by the time taken (t): a = v-u / t

4. Rearrange: Multiplying both sides by t: at=v-u 
Rearranging the terms gives the first equation of motion: v=u+at

Q6. Explain the concept of inertia with an example.  (3 Marks) 

Ans: Inertia is defined as the natural tendency of an undisturbed object to resist a change in its state of motion or of rest. This property is why Newton's First Law of Motion is also known as the Law of Inertia. Quantitatively, the mass of an object is a measure of its inertia.

Example (Braking):

Consider a passenger traveling in a motorcar:

1. While the car is moving, the passenger's body tends to remain in the state of motion.

2. When the driver suddenly applies brakes, the car slows down, but our body tends to continue in the same state of motion because of its inertia.

3. A sudden application of brakes may thus cause us to be thrown forward

Q7. (Internal Choice)  (3 Marks) 
Option 1: What is a suspension? Give two examples and one property. 
Option 2: Define centrifugation. Explain how this special technique is used to separate the components of milk.

Ans: Option 1: Suspension

A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Suspensions are generally non-homogeneous systems in which solids are dispersed in liquids.

Two Examples:

1. Chalk powder in water.

2. Muddy water (or simply Mud).

One Property: The particles of a suspension are visible to the naked eye. (Alternatively: The solute particles settle down when a suspension is left undisturbed, meaning a suspension is unstable
OR Option 2: Centrifugation
Centrifugation is a special technique of separation that can be used to separate colloidal particles. Colloidal particles are too small to be separated from the mixture by the process of conventional filtration.

Separation of Milk Components:

1. Nature of Milk: Milk is a colloidal solution (specifically an emulsion), where particles (such as fat globules) are uniformly spread throughout but do not settle down when left undisturbed.

2. Application: Because milk contains colloidal particles, the technique of centrifugation is used to separate components like cream from milk. This process uses rotational force to separate the components based on density difference, allowing the less dense particles (cream/fat) to be separated from the liquid medium.

Section D

Q1. (a) Explain the process of melting and factors affecting it. (3 marks) 
(b) Why does evaporation increase with an increase in surface area? (2 marks) 

Ans:  (a) Process of Melting (Fusion): Melting is the process where a solid changes to a liquid state. The minimum temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point. On increasing the temperature of solids, the kinetic energy of the particles increases. The energy supplied by heat overcomes the forces of attraction between the particles. The particles leave their fixed positions and start moving more freely, and a stage is reached when the solid is converted to a liquid.

Factors Affecting Melting:

1. Temperature: Higher temperature increases the melting rate.

2. Impurities: The presence of impurities lowers the melting point.

3. Pressure: Increased pressure may lower the melting point (e.g., ice).

(b)  Evaporation is defined as a surface phenomenon.

An increase in surface area increases the rate of evaporation because more liquid molecules are exposed to the atmosphere. Since evaporation occurs only from the surface, increasing the area of the surface (for example, by spreading clothes for drying up) allows more liquid particles to escape into the gaseous state, thereby increasing the rate of evaporation

Q2. (a) Describe the structure and functions of the Golgi apparatus in a cell. (3 marks) 
(b) Differentiate between smooth and rough endoplasmic reticulum (any four points). (2 marks) 

Ans: (a)  Golgi apparatus structure and functions: 

Structure: The Golgi apparatus consists of a system of membrane-bound vesicles (flattened sacs). These are arranged approximately parallel to each other in stacks called cisterns. These membranes often have connections with the membranes of the Endoplasmic Reticulum (ER).

Functions:

1. Packaging and Dispatch: The material synthesized near the ER is packaged and dispatched to various targets inside and outside the cell through the Golgi apparatus.

2. Storage and Modification: Its functions include the storage, modification and packaging of products in vesicles.

3. Sugar Synthesis: In some cases, complex sugars may be made from simple sugars in the Golgi apparatus.

4. Formation of Lysosomes: The Golgi apparatus is also involved in the formation of lysosomes

(b) Smooth vs. Rough endoplasmic reticulum:

Q3. (Internal Choice) 
Option 1: 
(a) Explain Newton's second law of motion and derive F = ma. (3 marks) 
(b) A body of mass 5 kg is acted upon by a force of 20 N. Calculate the acceleration and velocity after 4 seconds if it starts from rest. (2 marks) 

Ans: Newton's Second Law of Motion Explanation: The Second Law of Motion states that the rate of change of momentum of an object is proportional to the applied unbalanced force and acts in the direction of the force. This gives us a method to measure the force acting on an object as a product of its mass and acceleration.
Derivation of F = ma: Let force F produce acceleration a in mass m. Then, a ∝ F and a ∝ 1/m.
Thus, a = k · F /m, where k is a constant (taken as 1 in SI units).
Hence, F = ma.
(b) Calculation:
Given: m = 5 kg, F = 20 N, u = 0, t = 4 s.
Acceleration: a = F /m = 20/5 = 4 m/s².
Velocity: v = u + at = 0 + 4 × 4 = 16 m/s.

Option 2: 
Describe the three types of muscle tissues found in the animal body by differentiating them based on their structure, control (voluntary/involuntary), and specific location. (5 marks) 

Ans: 

Q4. Explain what is meant by uniform circular motion. Illustrate with an example, and derive the formula relating the speed (v) of an object moving in a circular path of radius (r) in time (t). (5 Marks)

Ans:  Uniform circular motion occurs when an object moves in a circular path with uniform speed. This motion is classified as accelerated motion because the direction of the velocity changes continuously. Since velocity is defined as speed with direction, the change in direction means the object's velocity is constantly changing, resulting in acceleration.

Example: The motion of the moon and the earth, or a cyclist on a circular track at constant speed, are examples of uniform circular motion.

Formula Derivation: If an object moves in a circular path of radius (r) and takes time (t) to complete one full revolution, the total distance travelled by the object is equal to the circumference of the circle, which is 2πr. The speed (v) is calculated by dividing the total distance travelled by the time taken. The formula relating the speed (v) of the object, the radius (r), and the time (t) is: 

Q5. Describe the types of connective tissues along with their functions.  (5 Marks) 

Ans: There are five types of connective tissues:
(i) Areolar connective tissue: It is a loose and cellular connective tissue. It joins skin to muscles, fills spaces inside organs, and is found around muscles, blood vessels, nerve and in the bone marrow.
Functions:
(a) It acts as a supporting and packing tissue between organs lying in the body cavity.
(b) It helps in repair of tissues after an injury.
(c) It also helps in combating foreign toxins.
(d) It fixes skin to underlying muscles.
(ii) Dense regular connective tissue: It is a fibrous connective tissue. It is characterised by ordered and densely packed collection
of fibres and cells. Dense regular connective tissue is the principal component of tendons and ligaments.
Functions:
(a) Tendons: Tendons are cord-like, strong, inelastic structures that join skeletal muscles to bones.
(b) Ligament: They are an elastic structure which connects bones to bones.
(iii) Adipose tissue: Adipose tissue is an aggregation of fat globules. The cells that primarily compose adipose tissue are called adipocytes or lipocytes or fat cells. The adipose tissue is abundant below the skin, between the internal organs and in the yellow bone marrow.
Functions:
(a) It serves as a reservoir of fat.
(b) It provides shape to the limbs and the body.
(c) It keeps visceral organs in position. It forms shock-absorbing cushions around kidneys and eyeballs.
(d) It acts as an insulator and reduces heat loss from body, i.e. it regulates body temperature.
(iv) Skeletal tissue: The skeletal or supporting tissue includes bone and cartilage which form the endoskeleton of vertebrate body.
(a) Cartilage: The cartilage is a specialised connective tissue which is compact and less vascular. Cartilage can be found in ear, nose tip, epiglottis, inter-vertebral discs, end of long bones, lower ends of ribs and rings of trachea. There are three varieties of cartilage - hyaline, elastic, and fibro-cartilage. The most abundant type is hyaline, found as supportive tissues in the nose, ears, trachea, larynx, and smaller respiratory tubes.
(b) Bone: Bone is very strong and non-flexible tissue. Bone cells are embedded in a hard matrix. Like cartilage, bone is a specialised connective tissue.
Functions:
(a) Cartilage provides support and flexibility to body parts such as ears and nose. It smoothens bone surfaces at the joints.
(b) Bone provides shape and skeletal support to body.
(c) Bone supports and protects vital body organs such as brain, lungs, etc.
(d) Bone anchors the muscles.
(v) Fluid connective tissue: Fluid connective tissue links the different parts of the body and maintains continuity in the body. It includes blood and lymph.
(a) Blood: In this tissue, cells move in a fluid or liquid matrix or medium called plasma. Blood flows in blood vessels called arteries, veins, and capillaries which are connected together to form the circulatory system. Blood contains red blood cells (RBCs), white blood cells (WBCs) and platelets suspended in the plasma.
(b) Lymph: Lymph is a colourless fluid that has filtered out of the blood capillaries.
Functions:
(a) Blood flows and transports gases, nutrients, hormones and vitamins to the tissues, and transports waste products from the tissues to the liver and the kidney.
(b) Lymph transports the nutrients (oxygen, glucose) that may have filtered out of the blood capillaries back into the heart to be recirculated in the body.
(c) Lymph brings CO₂ and nitrogenous wastes from tissues to the blood.