CBSE Class 9 Science Syllabus

Write the formula for molar mass and the number of particles using the mole concept.

Number of moles = given mass / molar mass = number of particles / 6.022 x 10^23.

Who discovered the cell and who coined the term, observing it in cork?

Robert Hooke discovered and coined the term 'cell' in 1665 while observing thin slices of cork under a microscope.

State the three main points of the cell theory.

All living organisms are composed of cells; the cell is the basic structural and functional unit of life; all cells arise from pre-existing cells. Proposed by Schleiden, Schwann, and Virchow.

Distinguish between prokaryotic and eukaryotic cells.

Prokaryotic cells have no true (membrane-bound) nucleus and lack membrane-bound organelles (e.g., bacteria). Eukaryotic cells have a true nucleus enclosed in a membrane and membrane-bound organelles (e.g., plant and animal cells).

Distinguish between a plant cell and an animal cell (three differences).

Plant cells have a cell wall, large central vacuole, and plastids (chloroplasts); animal cells lack a cell wall and plastids, have small/no vacuoles, and contain centrioles.

What is the function of the plasma (cell) membrane and what property does it have?

The plasma membrane separates the cell's contents from its surroundings and controls movement of substances in and out. It is selectively permeable.

Define osmosis.

Osmosis is the movement of water molecules from a region of higher water concentration to a region of lower water concentration through a selectively permeable membrane.

What happens to a cell placed in hypotonic, isotonic, and hypertonic solutions?

In a hypotonic solution the cell swells (gains water); in an isotonic solution there is no net change; in a hypertonic solution the cell shrinks/plasmolyses (loses water).

Why is the nucleus called the 'control centre' of the cell?

The nucleus contains chromosomes (DNA), which carry genetic information and control all cellular activities including cell division, growth, and inheritance.

Which organelle is called the 'powerhouse of the cell' and why?

Mitochondria, because they release energy in the form of ATP through cellular respiration.

What are ribosomes and what is their function?

Ribosomes are tiny granular organelles (sites of protein synthesis) found in the cytoplasm and attached to the rough endoplasmic reticulum.

Name the organelle called the 'suicidal bag' of the cell and state its function.

Lysosomes; they contain digestive enzymes that break down worn-out organelles and foreign material, and can digest the cell itself when damaged.

Define tissue.

A tissue is a group of cells similar in structure and origin that work together to perform a specific function.

Name the types of plant tissues and the two categories of meristematic tissue.

Plant tissues are meristematic (dividing) and permanent. Meristematic tissue is divided into apical, lateral (cambium), and intercalary meristems.

Name the three types of simple permanent tissue in plants and a key role of each.

Parenchyma (storage and photosynthesis), collenchyma (flexibility/mechanical support in growing parts), and sclerenchyma (rigidity and strength; dead cells).

Name the two complex permanent (conducting) tissues in plants and what each transports.

Xylem transports water and minerals from roots to leaves; phloem transports food (sugars) from leaves to other parts of the plant.

Name the four types of animal tissues.

Epithelial tissue, connective tissue, muscular tissue, and nervous tissue.

Name the three types of muscular tissue and state whether each is voluntary or involuntary.

Striated/skeletal muscle (voluntary), smooth/unstriated muscle (involuntary), and cardiac muscle (involuntary).

Give examples of connective tissue.

Blood, bone, cartilage, ligaments, tendons, and adipose (fat) tissue.

Distinguish between distance and displacement.

Distance is the total path length covered by a body (scalar, always positive). Displacement is the shortest straight-line distance from initial to final position with direction (vector, can be zero or negative).

Distinguish between speed and velocity, and define acceleration.

Speed is distance per unit time (scalar); velocity is displacement per unit time (vector). Acceleration is the rate of change of velocity with time (a = change in velocity / time).

Write the three equations of motion for uniformly accelerated motion.

v = u + at; s = ut + (1/2)at^2; v^2 = u^2 + 2as, where u = initial velocity, v = final velocity, a = acceleration, t = time, s = displacement.

What does the slope of a distance-time graph and a velocity-time graph represent?

The slope of a distance-time graph gives speed/velocity; the slope of a velocity-time graph gives acceleration. The area under a velocity-time graph gives displacement.

Define uniform circular motion and explain why it is accelerated motion.

Uniform circular motion is movement along a circular path at constant speed. It is accelerated because the direction of velocity changes continuously, so velocity changes.

State Newton's first law of motion and define inertia.

A body at rest stays at rest and a body in motion stays in uniform motion in a straight line unless acted upon by an external unbalanced force. Inertia is the tendency of a body to resist a change in its state of motion or rest.

State Newton's second law of motion and give its mathematical form.

The rate of change of momentum of a body is directly proportional to the applied force and occurs in the direction of the force. F = ma (force = mass x acceleration).

Define momentum and state its SI unit.

Momentum (p) is the product of an object's mass and velocity: p = mv. Its SI unit is kg m/s.

State Newton's third law of motion.

To every action there is an equal and opposite reaction; the forces act on two different bodies.

State the law of conservation of momentum.

In the absence of an external force, the total momentum of a system of objects remains constant; total momentum before collision equals total momentum after collision.

State the universal law of gravitation and its formula.

Every object attracts every other object with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them: F = G(m1 x m2)/r^2.

What is the value of the universal gravitational constant G, and of acceleration due to gravity g on Earth?

G = 6.674 x 10^-11 N m^2/kg^2; g = 9.8 m/s^2 (taken as ~9.8 or 10 m/s^2).

Distinguish between mass and weight.

Mass is the amount of matter in a body (constant everywhere, SI unit kg). Weight is the force with which Earth attracts a body, W = mg (varies with g, SI unit newton, N).

State Archimedes' principle and define buoyancy.

Archimedes' principle: when a body is immersed fully or partially in a fluid, it experiences an upward force equal to the weight of the fluid displaced. Buoyancy is this upward thrust exerted by a fluid on an object.

Define thrust and pressure, and give the SI unit of pressure.

Thrust is the force acting perpendicular to a surface. Pressure is thrust per unit area (P = F/A). SI unit of pressure is the pascal (Pa = N/m^2).

What is relative density, and why does an object float or sink in water?

Relative density = density of substance / density of water. An object floats if its density is less than that of water and sinks if its density is greater.

Name the natural resources that are essential physical resources for life and how each is purified naturally.

Air, water, and soil. Air pollutants are dispersed/diluted by wind; water is purified by the water cycle and self-cleaning; soil is renewed by weathering and biological activity.

What is the major cause of air pollution from burning fossil fuels, and name two harmful oxides produced.

Combustion of fossil fuels (coal, petroleum). Harmful oxides include oxides of nitrogen and sulphur (NOx and SO2), which cause acid rain, plus carbon dioxide and carbon monoxide.

What is acid rain and how is it formed?

Acid rain is rain that is more acidic than normal, formed when oxides of sulphur and nitrogen dissolve in rain water to form sulphuric and nitric acids.

How is soil formed and what is soil erosion?

Soil is formed over long periods by the breaking down (weathering) of rocks by sun, water, wind, and living organisms. Soil erosion is the removal of fertile topsoil by wind or flowing water.

What is humus and why is it important?

Humus is the rotting dead organic matter (decayed plants/animals) in soil. It increases soil fertility, water-holding capacity, and provides nutrients.

Describe the water cycle.

Water evaporates from water bodies and transpires from plants, condenses to form clouds, falls as precipitation (rain/snow), and returns to water bodies and groundwater, repeating the cycle.

Describe the carbon cycle.

Carbon circulates among atmosphere, living organisms, and environment via photosynthesis (CO2 to organic carbon), respiration, decomposition, combustion of fuels, and dissolution in oceans (returning CO2 to the atmosphere).

Describe the nitrogen cycle, naming the key processes.

Atmospheric nitrogen is converted to usable forms by nitrogen fixation (by Rhizobium bacteria and lightning), then nitrification, uptake by plants (assimilation), ammonification by decomposers, and returned to the atmosphere by denitrification.

Describe the oxygen cycle.

Oxygen is released into the atmosphere by photosynthesis and is removed by respiration, combustion, and the formation of oxides; the atmosphere stays roughly balanced.

What is the greenhouse effect and which gases are responsible?

The greenhouse effect is the trapping of heat by certain atmospheric gases, keeping Earth warm. Greenhouse gases include carbon dioxide, methane, and water vapour; their excess causes global warming.

What is the ozone layer and why is it important?

The ozone layer (in the upper atmosphere) is made of O3 and shields Earth from harmful ultraviolet (UV) radiation from the Sun.

What are the two main sources of food for humans?

Plants (agriculture - crops, fruits, vegetables) and animals (animal husbandry - milk, eggs, meat, fish).

Define crop, and distinguish between Kharif and Rabi crops.

A crop is the same kind of plants grown and cultivated together at a place on a large scale. Kharif crops are grown in the rainy season (June-October), e.g., paddy, maize; Rabi crops are grown in winter (October-March), e.g., wheat, gram.

Name the macronutrients and micronutrients required by plants.

Macronutrients (needed in large amounts): nitrogen, phosphorus, potassium, calcium, magnesium, sulphur. Micronutrients (needed in small amounts): iron, manganese, boron, zinc, copper, molybdenum, chlorine.

Distinguish between manure and fertilisers.

Manure is natural organic matter (decomposed plant/animal waste) that adds humus and nutrients; fertilisers are commercially produced inorganic chemicals rich in specific nutrients (N, P, K) but add no humus.

What is crop rotation and how does mixed/intercropping differ?

Crop rotation is growing different crops alternately on the same field to maintain soil fertility. Mixed cropping is growing two or more crops together; intercropping is growing them in a definite row pattern.

What are the three main methods of crop variety improvement?

Hybridisation (crossing genetically different plants), selection, and introduction of genes (genetic modification) to obtain desired traits like higher yield and disease resistance.

Name the three main types of crop pests/storage losses and how stored grains are protected.

Losses are caused by insects, rodents, and microorganisms (fungi/bacteria), plus moisture and temperature. Protection includes proper drying, fumigation, and storage in clean, dry, airtight conditions (e.g., silos, godowns).

What is animal husbandry?

Animal husbandry is the scientific management of animal livestock, including feeding, breeding, shelter, and disease control, to obtain food and other products.

Distinguish between exotic, indigenous (desi), and cross-bred cattle.

Indigenous (desi) breeds have good disease resistance; exotic/foreign breeds have long lactation periods and high milk yield; cross-breeds combine both traits (high yield plus resistance).

What are broilers and layers in poultry farming?

Broilers are chickens raised for meat (fast growth, high feed efficiency); layers are hens raised for egg production.

What is composite fish culture?

A system of fish farming in which several compatible fish species with different feeding habits are reared together in a single pond so all food zones of the pond are used efficiently.

Distinguish between capture fishing and culture fishery (aquaculture), and define mariculture.

Capture fishing is obtaining fish from natural water bodies; culture fishery (aquaculture) is breeding and rearing fish in controlled conditions. Mariculture is the culture of marine fish in seawater.

What is apiculture and name a common bee variety used in India for high honey yield.

Apiculture is the rearing of honeybees (bee-keeping) for honey and wax. Apis mellifera (Italian bee) is commonly used for high honey production.