🇮🇳National Mega Defence Deal: The Indian Government has cleared a massive ₹3.25 lakh crore deal for the procurement of 114 Rafale fighter jets to strengthen the Indian Air Force’s strategic capabilities. Maritime Security: Approval has also been granted for the acquisition of additional P-8I submarine hunter aircraft to enhance naval surveillance in the Indian Ocean Region. Railway Infrastructure: The Ministry of Railways has sanctioned projects worth ₹1,334 crore across Uttar Pradesh, Rajasthan, Madhya Pradesh, and West Bengal to improve connectivity. Gender Milestone: After 145 years, the Darjeeling Toy Train (DHR) has appointed its first-ever woman ticket examiner. Nuclear Energy: NTPC is collaborating with CCTE for the development of ANEEL, an indigenous thorium-based nuclear fuel, to boost India’s energy security. 🌍International Bangladesh Elections: Voting has concluded in the high-stakes general elections; the international community is closely monitoring the results amid reports of sporadic violence. Saudi-Qatar Rail Link: An ambitious 785 km high-speed bullet train project has been outlined to connect Riyadh and Doha, reducing travel time to just two hours. Indo-US Ties: US President Donald Trump has hailed a landmark trade agreement with India as 'historic', aimed at boosting bilateral investment and strategic ties. Cambodia Cyber Fraud: Authorities in Cambodia busted a 'digital arrest' scam hub where fake Indian police uniforms and Gandhi portraits were seized. 💰Economy GDP Growth: India is projected to maintain its position as the fastest-growing G-20 economy with a growth rate of 6.4%. Corporate Results: Major PSUs and firms including Coal India, ONGC, HAL, and IRCTC are set to announce their Q3 financial performance today. Trade Engagement: India’s trade deals with the US, UK, and EU are expected to significantly accelerate the Viksit Bharat mission and boost auto component exports. 🗓️Date’s importance National Women’s Day (India): Observed on 13 February to commemorate the birth anniversary of Sarojini Naidu, the 'Nightingale of India'. World Radio Day: Celebrated globally to recognise the unique power of radio in connecting people and providing information. 👱‍♂️👩‍🦳Person of the day Sarojini Naidu: Born on 13 February 1879, she was a prominent independence activist and poet. She was the first Indian woman to become the President of the Indian National Congress (1925) and the first woman Governor of an Indian state (United Provinces). 🏅Sports Asian Shooting Championship: India’s Tomar clinched the Gold medal as India swept the podium in the Men’s 50m Rifle 3 Positions event. Hockey Rivalry: On the sidelines of the Winter Olympics preparations, a high-intensity clash between Finland and Sweden is scheduled for today. Neeraj Chopra: The Sports Ministry has approved an extended high-performance training camp for Olympic champion Neeraj Chopra in South Africa. 🏆Awards AAVMC 2026 Awards: John J. Dascanio (Texas Tech University) has been named the recipient of the Distinguished Veterinary Educator Award for 2026. Walter Payton NFL Man of the Year: Washington Commanders' Bobby Wagner has been honoured for his community service and excellence on the field. ⭐️Other important significance Goa Carnival 2026: The world-famous Goa Carnival kicks off today (13 February), featuring colourful parades and cultural festivities across the state. CBSE Update: The board is set to conduct a live webcast today regarding the revised exam patterns and on-screen marking for the 2026 Board Exams. 📚Word of the day Fortuitous (Adjective) Meaning: Happening by a lucky chance rather than intention. Usage: Meeting the mentor at the conference proved to be a fortuitous event for his career.  

1) 🇮🇳National   Right to Recall Law: AAP MP Raghav Chadha has called for the introduction of a legal provision in Parliament to enact a 'Right to Recall' law. This would allow voters to remove elected representatives before the end of their term to strengthen democratic accountability. Assam Electoral Roll: Assam has released its final voter list following a Special Summary Revision, which saw over 2.4 lakh additional names dropped from the rolls after thorough scrutiny and verification. CBSE Exam Reforms: Starting from the 2026 session, CBSE will implement On-Screen Marking (OSM) for the evaluation of Class 12 answer books to ensure faster and more transparent results. Additionally, Class 10 will now have two board exams (Feb-March and May). Skill India Investigation: The government has registered FIRs against 41 Skill India training centres following a CAG report that flagged serious irregularities in the implementation of various skill development schemes. 2) 🌍International French President’s Visit: President Emmanuel Macron is scheduled to visit India on 17 February. Discussions are expected to focus on high-level defence cooperation, trade, and strategic partnerships. Bangladesh General Elections: Bangladesh is heading into high-stakes national elections with heightened security across thousands of sensitive polling centres, marking 18 months since the 2024 student uprising. FAA Grounding in Texas: All flights were temporarily grounded at El Paso International Airport following a security directive issued by the Federal Aviation Administration (FAA), causing significant air traffic disruption. 3) 💰Economy AI Labelling Norms: The government has notified updated regulations for digital platforms, mandating prominent AI-generated content labels and setting a strict three-hour deadline for platforms to block unlawful material. Pilot Fatigue Rules: Airline major IndiGo has informed the DGCA that it is fully prepared to comply with revised pilot fatigue and duty time norms, following the expiration of temporary exemptions. Railway Modernisation: Indian Railways has announced plans to manufacture 260 Vande Bharat sleeper trainsets to modernise long-distance overnight travel across the country. 4) 🗓️Date’s importance Hug Day: Celebrated globally on 12 February as the sixth day of Valentine’s Week, focusing on the power of physical closeness and emotional support. National Productivity Day: Observed in India on 12 February to commemorate the establishment of the National Productivity Council (NPC) and to promote productivity culture in India. Darwin Day: Observed internationally to commemorate the birthday of Charles Darwin (born 1809) and his contributions to science and evolutionary biology. 5) 👱‍♂️👩‍🦳Person of the day Emmanuel Macron: The French President is the focus of diplomatic news ahead of his significant visit to India to bolster the Indo-French strategic partnership. Raghav Chadha: The AAP leader is in the spotlight for pushing the 'Right to Recall' legislation in the Indian Parliament. 6) 🏅Sports T20 World Cup Preview: South Africa and Afghanistan have emerged as strong contenders in the ongoing T20 World Cup, with Afghanistan aiming to continue its historic rise in global cricket. Chess Calendar Clash: Grandmaster R Praggnanandhaa and six other leading players have raised concerns over scheduling conflicts in the 2026 international circuit, warning that overlapping tournaments could hinder preparation. PCB Force Majeure: The Pakistan Cricket Board (PCB) is reportedly considering the 'Force Majeure' clause in its defense against potential ICC sanctions for withdrawing from its match against India in Colombo. 7) 🏆Awards NFL Honors 2026: The ceremony held in San Francisco saw Matthew Stafford win the AP Most Valuable Player (MVP) award, while Myles Garrett was named Defensive Player of the Year. Protector of the Year: A new award introduced this year by the NFL to recognise the league's top offensive lineman. 8) ⭐️Other important significance Free Power in J&K: Lieutenant Governor Manoj Sinha has approved the rollout of 200 units of free electricityfor Antyodaya Anna Yojana (AAY) households in Jammu and Kashmir. Trilateral Peace Talks: Abu Dhabi hosted a second round of trilateral talks between Ukraine, Russia, and the US to explore pathways for de-escalating the conflict. 📚Word of the day Improvident (Adjective) Meaning: Lacking foresight; failing to plan for the future, especially regarding money. Usage: "The committee criticised the improvident use of public funds during the project's initial phase."  

1) Motion (Kinematics, Speed, and Velocity) Motion Motion is the change in position of an object with respect to time and a reference point. Distance and Displacement Distance: Total path covered (scalar quantity). Displacement: Shortest straight-line distance between initial and final position (vector quantity). Speed Speed = Distance / Time SI Unit: m/s Scalar quantity Average Speed = Total distance / Total time Velocity Velocity = Displacement / Time Vector quantity (has magnitude and direction) Average Velocity = Total displacement / Total time Acceleration Acceleration = Change in velocity / Time SI Unit: m/s² Positive acceleration → Increase in speed Negative acceleration → Retardation Equations of Motion (Uniform Acceleration) v = u + at s = ut + ½at² v² = u² + 2as Where: u = initial velocity v = final velocity a = acceleration t = time s = displacement   2) Laws of Motion and Friction Newton’s Laws of Motion Given by Isaac Newton First Law (Law of Inertia) A body continues in its state of rest or uniform motion unless acted upon by an external force. Second Law Force = Mass × Acceleration F = ma Third Law Every action has an equal and opposite reaction. Momentum Momentum = Mass × Velocity SI Unit: kg·m/s Friction Force opposing relative motion between surfaces in contact. Types: Static friction Sliding friction Rolling friction Friction depends on: Nature of surfaces Normal reaction   3) Work, Power, and Energy Work Work = Force × Displacement (in direction of force) W = F × s SI Unit: Joule (J) 1 Joule = Work done by 1 N force moving object by 1 m. Power Power = Work / Time SI Unit: Watt (W) 1 Horsepower = 746 W Energy Capacity to do work. SI Unit: Joule Types: Kinetic Energy (KE) = ½mv² Potential Energy (PE) = mgh Law of Conservation of Energy Energy can neither be created nor destroyed; it only changes form.   4) Gravitation Universal Law of Gravitation Proposed by Isaac Newton F = Gm₁m₂ / r² G = 6.67 × 10⁻¹¹ N·m²/kg² Acceleration Due to Gravity g ≈ 9.8 m/s² g decreases: At higher altitudes At equator Escape Velocity Escape velocity of Earth = 11.2 km/s   5) Mass, Weight, and Density Mass Quantity of matter SI Unit: kg Same everywhere Weight Weight = mg Depends on gravity SI Unit: Newton Density Density = Mass / Volume SI Unit: kg/m³ Density of water = 1000 kg/m³ Relative Density = Density of substance / Density of water   6) Pressure and Buoyancy Pressure Pressure = Force / Area SI Unit: Pascal (Pa) 1 Pa = 1 N/m² Atmospheric Pressure Due to weight of air column; measured using a barometer. Buoyancy Upward force exerted by fluid on immersed object. Archimedes’ Principle Given by Archimedes A body immersed in a fluid experiences an upward force equal to the weight of the displaced fluid. Applications: Floating of ships Hydrometer Submarines   7) Sound and Wave Motion Wave Transfer of energy without transfer of matter. Types: Mechanical waves Electromagnetic waves Wave Terms Wavelength (λ) Frequency (f) Time Period (T) Amplitude Wave equation: v = fλ Sound Produced by vibrations Cannot travel in vacuum Speed in air ≈ 340 m/s Factors affecting speed: Temperature Medium   8) Heat and Temperature Heat Energy transferred due to temperature difference. Units: Joule (SI) Calorie 1 calorie = 4.186 J Temperature Scales Celsius (°C) Kelvin (K) Fahrenheit (°F) Conversion: K = °C + 273 Modes of Heat Transfer Conduction (solids) Convection (fluids) Radiation (no medium required)   9) Light (Reflection, Refraction, Lenses, Mirrors) Reflection Laws: Angle of incidence = Angle of reflection Incident ray, reflected ray, and normal lie in same plane Mirrors Plane mirror → Virtual, erect image Concave mirror → Real & inverted (generally) Convex mirror → Virtual & diminished Mirror Formula: 1/f = 1/v + 1/u   Refraction Bending of light when passing from one medium to another. Snell’s Law: n₁ sin i = n₂ sin r Refractive index: n = Speed in vacuum / Speed in medium Lenses Lens Formula: 1/f = 1/v − 1/u Power of lens: P = 1/f (in meter) Unit: Diopter   10) Electricity and Magnetism Electric Current I = Q / t Unit: Ampere Potential Difference Unit: Volt Ohm’s Law V = IR Electric Power P = VI Unit: Watt   Magnetism Like poles repel; unlike poles attract Magnetic field lines go from North to South Electromagnets work due to electric current Right-hand thumb rule gives direction of magnetic field around conductor.   11) Units and Measurements SI Base Units Length → meter (m) Mass → kilogram (kg) Time → second (s) Current → ampere (A) Temperature → kelvin (K) Luminous intensity → candela (cd) Amount of substance → mole (mol) Derived Units Force → Newton Energy → Joule Power → Watt Pressure → Pascal Important Conversions 1 km = 1000 m 1 hour = 3600 s 1 N = 1 kg·m/s² 1) Matter and Its States Definition of Matter Matter is anything that has mass and occupies space. Characteristics of Particles of Matter Very small in size Have spaces between them Continuously moving (possess kinetic energy) Attract one another (intermolecular force)   Physical Properties of Matter Mass Volume Density (Density = Mass / Volume) State   States of Matter 1. Solid Definite shape and volume Strong intermolecular force Very small spaces between particles Least compressible 2. Liquid Definite volume but no fixed shape Moderate intermolecular force Slightly compressible Can flow 3. Gas No definite shape or volume Very weak intermolecular force Highly compressible High kinetic energy   Change of State Change of state occurs due to temperature or pressure change. Melting: Solid → Liquid Freezing: Liquid → Solid Boiling/Vaporization: Liquid → Gas Condensation: Gas → Liquid Sublimation: Solid → Gas directly   Latent Heat Heat absorbed or released during change of state without change in temperature. Latent heat of fusion Latent heat of vaporization   2) Atomic Structure and Molecules Structure of Atom The nuclear model was proposed by Ernest Rutherford. An atom consists of: Protons (positive charge) Neutrons (no charge) Electrons (negative charge) Protons and neutrons are present in the nucleus; electrons revolve in fixed shells or energy levels.   Important Terms Atomic Number (Z) Number of protons in an atom. Mass Number (A) Number of protons + neutrons. A = p + n Isotopes Atoms of the same element having same atomic number but different mass numbers.   Electronic Configuration Maximum electrons in a shell = 2n² (where n = shell number) K shell = 2 L shell = 8 M shell = 18   Valency Combining capacity of an atom. Determined by electrons in the outermost shell (valence electrons).   Molecules Smallest particle of a substance that can exist independently. Types: Homoatomic (O₂, N₂) Heteroatomic (H₂O, CO₂)   3) Chemical Reactions and Equations Chemical Reaction A process in which new substances are formed with new chemical properties. Indicators of reaction: Change in colour Change in temperature Gas evolution Formation of precipitate   Chemical Equation Symbolic representation of a chemical reaction. Example: 2H₂ + O₂ → 2H₂O It must be balanced according to the Law of Conservation of Mass.   Types of Chemical Reactions Combination Reaction A + B → AB Decomposition Reaction AB → A + B Displacement Reaction A + BC → AC + B Double Displacement Reaction AB + CD → AD + CB Redox Reaction Oxidation and reduction occur simultaneously.   Oxidation Addition of oxygen Removal of hydrogen Loss of electrons Reduction Removal of oxygen Addition of hydrogen Gain of electrons   4) Acids, Bases, and Salts Acids Substances that produce H⁺ ions in aqueous solution. Examples: HCl, H₂SO₄, HNO₃ Properties: Sour taste Turn blue litmus red pH < 7   Bases Substances that produce OH⁻ ions in aqueous solution. Examples: NaOH, KOH Properties: Bitter taste Turn red litmus blue pH > 7   Salts Formed by neutralization reaction. Acid + Base → Salt + Water Example: HCl + NaOH → NaCl + H₂O   pH Scale Range: 0 to 14 7 → Neutral < 7 → Acidic 7 → Basic   5) Metals and Non-Metals Physical Properties of Metals Lustrous Malleable Ductile Good conductors of heat and electricity Sonorous   Chemical Properties of Metals React with oxygen → Metal oxides React with water → Hydrogen gas React with acids → Salt + Hydrogen   Non-Metals Brittle Poor conductors Not sonorous Form acidic oxides   Reactivity Series K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au More reactive metals displace less reactive metals from their compounds.   Corrosion Slow destruction of metals due to reaction with environment (e.g., rusting of iron).   6) Carbon and Its Compounds Properties of Carbon Tetravalent Forms covalent bonds Shows catenation (self-linking ability)   Allotropes of Carbon Diamond Graphite Fullerene   Hydrocarbons Compounds containing only carbon and hydrogen. Alkanes → Single bonds Alkenes → Double bonds Alkynes → Triple bonds   Functional Groups –OH → Alcohol –COOH → Carboxylic acid –CHO → Aldehyde –CO– → Ketone   7) Periodic Classification of Elements The periodic table was first systematically arranged by Dmitri Mendeleev.   Modern Periodic Law Properties of elements are periodic functions of their atomic numbers.   Structure of Modern Periodic Table 7 Periods (rows) 18 Groups (columns)   Important Periodic Trends Across a Period: Atomic size decreases Metallic character decreases Electronegativity increases Down a Group: Atomic size increases Metallic character increases   8) Common Chemical Formulae and Their Uses Water → H₂O → Universal solvent Common salt → NaCl → Food seasoning Baking soda → NaHCO₃ → Baking, antacid Washing soda → Na₂CO₃·10H₂O → Cleaning agent Bleaching powder → CaOCl₂ → Disinfectant Ammonia → NH₃ → Fertilizer production Sulphuric acid → H₂SO₄ → Car batteries Hydrochloric acid → HCl → Laboratory reagent Nitric acid → HNO₃ → Fertilizers   1) Cell: The Fundamental Unit of Life Discovery of Cell The cell was first observed by Robert Hooke in 1665 while examining cork under a microscope. Cell Theory Proposed by Matthias Schleiden and Theodor Schwann. Cell theory states: All living organisms are made up of cells. Cell is the basic structural and functional unit of life. New cells arise from pre-existing cells.   Types of Cells Prokaryotic Cells No true nucleus No membrane-bound organelles Example: Bacteria Eukaryotic Cells True nucleus present Membrane-bound organelles present Example: Plant and animal cells   Structure of Cell 1. Cell Membrane Selectively permeable Controls movement of substances 2. Cell Wall (Plant cells only) Provides rigidity and protection 3. Cytoplasm Jelly-like substance Site of metabolic activities 4. Nucleus Control center Contains genetic material (DNA) 5. Mitochondria “Powerhouse of the cell” Site of respiration 6. Ribosomes Protein synthesis 7. Endoplasmic Reticulum (ER) Rough ER → Protein synthesis Smooth ER → Lipid synthesis 8. Golgi Apparatus Packaging and secretion 9. Lysosomes “Suicide bags” Intracellular digestion 10. Chloroplast (Plant cells) Site of photosynthesis   2) Plant and Animal Tissues Tissue Group of similar cells performing a specific function. Plant Tissues A) Meristematic Tissue Actively dividing cells Types: Apical, Intercalary, Lateral B) Permanent Tissue Simple (Parenchyma, Collenchyma, Sclerenchyma) Complex (Xylem and Phloem) Xylem → Transports water Phloem → Transports food   Animal Tissues Epithelial Tissue → Protective covering Connective Tissue → Support (Blood, Bone, Cartilage) Muscular Tissue → Movement Nervous Tissue → Control and coordination 3) Diversity in Living Organisms Classification Organisms are classified based on similarities and differences. Five Kingdom Classification proposed by Robert H. Whittaker: Monera Protista Fungi Plantae Animalia Basis of Classification Cell structure Mode of nutrition Body organization Reproduction   4) Life Processes 1. Nutrition Autotrophic Nutrition Plants prepare food by photosynthesis. Photosynthesis equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ Heterotrophic Nutrition Organisms depend on others for food. Types: Holozoic Saprophytic Parasitic   2. Respiration Process of breaking down food to release energy. Aerobic respiration: Glucose + Oxygen → CO₂ + H₂O + Energy Anaerobic respiration occurs without oxygen.   3. Transportation In Plants Xylem → Water Phloem → Food In Humans Circulatory system Heart pumps blood Blood carries oxygen and nutrients   4. Excretion Removal of metabolic wastes. In Humans: Kidneys → Urine formation Lungs → CO₂ removal Skin → Sweat   5) Control and Coordination Nervous System Components: Brain Spinal cord Nerves Brain parts: Cerebrum → Thinking Cerebellum → Balance Medulla → Involuntary actions Reflex action is rapid, automatic response.   Endocrine System Hormones are chemical messengers. Important glands: Pituitary (Master gland) Thyroid Adrenal Pancreas Hormones regulate growth, metabolism, reproduction.   6) Reproduction in Plants and Animals Asexual Reproduction Single parent involved. Types: Binary fission Budding Spore formation Vegetative propagation   Sexual Reproduction Two parents involved. Involves fusion of male and female gametes. In humans: Fertilization Zygote formation Embryo development   7) Heredity and Evolution Heredity Transmission of traits from parents to offspring. Laws of inheritance given by Gregor Mendel: Law of Dominance Law of Segregation Law of Independent Assortment   Genes Units of heredity present on chromosomes.   Evolution Gradual change in organisms over generations. Theory of Natural Selection proposed by Charles Darwin. Key idea: Survival of the fittest.   8) Human Diseases, Causes, and Prevention Types of Diseases Communicable Diseases Spread by pathogens. Examples: Tuberculosis, Malaria Non-Communicable Diseases Not infectious. Examples: Diabetes, Cancer   Causes Bacteria Viruses Fungi Protozoa Nutritional deficiency   Prevention Vaccination Hygiene Balanced diet Safe drinking water Exercise   9) Our Environment and Ecosystems Environment Surroundings in which organisms live.   Ecosystem Interaction between living (biotic) and non-living (abiotic) components.   Components of Ecosystem Producers → Green plants Consumers → Herbivores, carnivores Decomposers → Bacteria and fungi   Food Chain Producers → Primary consumers → Secondary consumers Food Web Interconnected food chains.   Ozone Layer Protects Earth from harmful UV radiation. Environmental Issues Pollution Global warming Deforestation     100 Model Questions Q.1) What is the SI unit of force? Answer: Newton Explanation: Force is measured in Newton (N). One Newton is the force required to produce an acceleration of 1 m/s² in a body of mass 1 kg. Q.2) Define velocity. Answer: Displacement per unit time Explanation: Velocity is a vector quantity defined as displacement divided by time. It includes both magnitude and direction. Q.3) What is acceleration due to gravity on Earth? Answer: 9.8 m/s² Explanation: The acceleration due to gravity near Earth’s surface is approximately 9.8 m/s². Q.4) State Newton’s First Law of Motion. Answer: A body remains at rest or in uniform motion unless acted upon by an external force. Explanation: This law is also called the law of inertia and explains resistance to change in motion. Q.5) What is momentum? Answer: Product of mass and velocity Explanation: Momentum = mass × velocity and is measured in kg·m/s. Q.6) What is the SI unit of energy? Answer: Joule Explanation: Energy is measured in Joules (J) in the SI system. Q.7) Write the formula for kinetic energy. Answer: ½mv² Explanation: Kinetic energy depends on mass and square of velocity. Q.8) What is potential energy? Answer: Energy possessed due to position Explanation: Example: mgh represents gravitational potential energy. Q.9) State Ohm’s Law. Answer: V = IR Explanation: Voltage across a conductor is directly proportional to current when temperature remains constant. Q.10) What is the SI unit of electric current? Answer: Ampere Explanation: Current is measured in amperes (A). Q.11) What type of lens is used to correct myopia? Answer: Concave lens Explanation: Myopia (short-sightedness) is corrected using a diverging (concave) lens. Q.12) Define density. Answer: Mass per unit volume Explanation: Density = Mass / Volume, SI unit is kg/m³. Q.13) What is Archimedes’ Principle? Answer: A body immersed in a fluid experiences an upward force equal to the weight of displaced fluid. Explanation: This explains floating of ships and submarines. Q.14) What is the speed of sound in air? Answer: Approximately 340 m/s Explanation: Sound travels at about 340 m/s in air at room temperature. Q.15) What is reflection of light? Answer: Bouncing back of light from a surface Explanation: The angle of incidence equals the angle of reflection. Q.16) What is refraction? Answer: Bending of light when it passes from one medium to another Explanation: Caused by change in speed of light. Q.17) What is the SI unit of pressure? Answer: Pascal Explanation: 1 Pascal = 1 N/m². Q.18) Define power. Answer: Work done per unit time Explanation: SI unit is Watt. Q.19) What is latent heat? Answer: Heat absorbed or released without temperature change Explanation: Occurs during change of state. Q.20) What is universal law of gravitation? Answer: Every two masses attract each other with a force proportional to product of their masses and inversely proportional to square of distance between them. Explanation: Given by Newton. Q.21) What is matter? Answer: Anything that has mass and occupies space Explanation: All physical substances are matter. Q.22) Name the three states of matter. Answer: Solid, Liquid, Gas Explanation: Based on particle arrangement and intermolecular force. Q.23) What is atomic number? Answer: Number of protons in an atom Explanation: It determines identity of an element. Q.24) What is mass number? Answer: Sum of protons and neutrons Explanation: A = p + n. Q.25) Define valency. Answer: Combining capacity of an element Explanation: Depends on electrons in outermost shell. Q.26) What is an isotope? Answer: Atoms of same element with different mass numbers Explanation: They have same atomic number. Q.27) What is a molecule? Answer: Smallest particle of a substance that can exist independently Explanation: Example: H₂O. Q.28) What is a chemical reaction? Answer: Process in which new substances are formed Explanation: Involves breaking and making of bonds. Q.29) What is oxidation? Answer: Addition of oxygen or loss of electrons Explanation: Opposite of reduction. Q.30) Define reduction. Answer: Removal of oxygen or gain of electrons Explanation: Occurs along with oxidation. Q.31) What is pH value of a neutral solution? Answer: 7 Explanation: Pure water has pH 7. Q.32) What is an acid? Answer: Substance that produces H⁺ ions in solution Explanation: Example: HCl. Q.33) What is a base? Answer: Substance that produces OH⁻ ions in solution Explanation: Example: NaOH. Q.34) What is neutralization? Answer: Reaction between acid and base forming salt and water Explanation: Example: HCl + NaOH. Q.35) What is corrosion? Answer: Slow destruction of metals by chemical reaction Explanation: Rusting is example. Q.36) Name the gas evolved when metal reacts with acid. Answer: Hydrogen Explanation: Metal + Acid → Salt + Hydrogen. Q.37) What is the reactivity series? Answer: Arrangement of metals in decreasing order of reactivity Explanation: Used to predict displacement reactions. Q.38) What is catenation? Answer: Ability of carbon to form long chains Explanation: Due to strong C–C bonds. Q.39) Name the functional group –OH. Answer: Alcohol Explanation: Presence of –OH indicates alcohol. Q.40) Who proposed modern periodic law? Answer: Henry Moseley Explanation: Based on atomic number. Q.41) Who discovered the cell? Answer: Robert Hooke Explanation: Observed cork cells in 1665. Q.42) What is the basic unit of life? Answer: Cell Explanation: All organisms are made of cells. Q.43) What is the powerhouse of the cell? Answer: Mitochondria Explanation: Site of respiration and ATP production. Q.44) What contains genetic material in a cell? Answer: Nucleus Explanation: Contains DNA. Q.45) What is tissue? Answer: Group of similar cells performing a specific function Explanation: Example: Muscular tissue. Q.46) What transports water in plants? Answer: Xylem Explanation: Conducts water from roots to leaves. Q.47) What transports food in plants? Answer: Phloem Explanation: Carries food from leaves to other parts. Q.48) What is photosynthesis? Answer: Process by which plants make food using sunlight Explanation: Produces glucose and oxygen. Q.49) What is respiration? Answer: Breakdown of food to release energy Explanation: Occurs in mitochondria. Q.50) What is excretion? Answer: Removal of metabolic wastes Explanation: Kidneys help in excretion. (Continuing…) Q.51) What is heredity? Answer: Transmission of traits from parents to offspring Explanation: Governed by genes. Q.52) Who is known as the Father of Genetics? Answer: Gregor Mendel Explanation: Proposed laws of inheritance. Q.53) What is evolution? Answer: Gradual change in organisms over generations Explanation: Explained by natural selection. Q.54) Name the organ that pumps blood. Answer: Heart Explanation: Pumps blood throughout body. Q.55) What are communicable diseases? Answer: Diseases that spread from person to person Explanation: Example: Tuberculosis. Q.56) What causes malaria? Answer: Plasmodium Explanation: Transmitted by female Anopheles mosquito. Q.57) What is ecosystem? Answer: Interaction between living and non-living components Explanation: Includes biotic and abiotic factors. Q.58) What are producers in ecosystem? Answer: Green plants Explanation: They prepare their own food. Q.59) What is food chain? Answer: Sequence of organisms where each is eaten by the next Explanation: Shows energy flow. Q.60) What protects Earth from UV rays? Answer: Ozone layer Explanation: Absorbs harmful ultraviolet radiation. Q.61) What is the SI unit of work? Answer: Joule Explanation: Work is said to be done when a force causes displacement. Its SI unit is Joule (J), equal to 1 Newton × 1 meter. Q.62) Define displacement. Answer: Shortest distance between initial and final position Explanation: Displacement is a vector quantity and includes direction. Q.63) What is friction? Answer: Force opposing relative motion between surfaces in contact Explanation: Friction always acts opposite to the direction of motion. Q.64) What is the formula for pressure? Answer: Force divided by area Explanation: Pressure = Force / Area and is measured in Pascal. Q.65) What is the unit of frequency? Answer: Hertz Explanation: Frequency is the number of vibrations per second. Q.66) What is the unit of electric power? Answer: Watt Explanation: Electric power = Voltage × Current. Q.67) What is the mirror formula? Answer: 1/f = 1/v + 1/u Explanation: It relates focal length, image distance, and object distance. Q.68) Which mirror is used as rear-view mirror in vehicles? Answer: Convex mirror Explanation: It provides a wider field of view and forms diminished images. Q.69) What is boiling point of water at standard atmospheric pressure? Answer: 100°C Explanation: Water boils at 100°C under normal atmospheric pressure. Q.70) What is the SI unit of temperature? Answer: Kelvin Explanation: Kelvin is the SI unit used in scientific measurements. Q.71) What is sublimation? Answer: Direct change of solid into gas Explanation: Example: Camphor and dry ice. Q.72) What is the maximum number of electrons in K shell? Answer: 2 Explanation: According to 2n² rule, K shell (n=1) holds 2 electrons. Q.73) What is a balanced chemical equation? Answer: Equation with equal number of atoms on both sides Explanation: It obeys law of conservation of mass. Q.74) What is the chemical formula of washing soda? Answer: Na₂CO₃·10H₂O Explanation: It is sodium carbonate decahydrate. Q.75) What is the chemical formula of baking soda? Answer: NaHCO₃ Explanation: It is sodium hydrogen carbonate. Q.76) What is the pH value of an acidic solution? Answer: Less than 7 Explanation: Acids have pH below 7. Q.77) What type of oxide is formed by non-metals? Answer: Acidic oxide Explanation: Example: CO₂ forms carbonic acid in water. Q.78) What is galvanization? Answer: Coating iron with zinc Explanation: Prevents rusting. Q.79) What is the valency of carbon? Answer: 4 Explanation: Carbon is tetravalent. Q.80) What determines the position of an element in periodic table? Answer: Atomic number Explanation: Modern periodic law is based on atomic number. Q.81) What is the function of ribosomes? Answer: Protein synthesis Explanation: Ribosomes are sites of protein formation. Q.82) What is the control center of the cell? Answer: Nucleus Explanation: It regulates all cell activities. Q.83) What is meristematic tissue? Answer: Actively dividing plant tissue Explanation: Responsible for plant growth. Q.84) What type of tissue is blood? Answer: Connective tissue Explanation: Blood connects different parts of the body. Q.85) What is autotrophic nutrition? Answer: Mode of nutrition in which organisms make their own food Explanation: Example: Green plants. Q.86) What is anaerobic respiration? Answer: Respiration without oxygen Explanation: Produces less energy and may produce alcohol or lactic acid. Q.87) What is the main excretory organ in humans? Answer: Kidney Explanation: Kidneys filter blood and form urine. Q.88) What is reflex action? Answer: Rapid automatic response to stimulus Explanation: Controlled by spinal cord. Q.89) Which hormone regulates blood sugar level? Answer: Insulin Explanation: Secreted by pancreas. Q.90) What is vegetative propagation? Answer: Asexual reproduction in plants through vegetative parts Explanation: Example: Potato through tuber. Q.91) What is fertilization? Answer: Fusion of male and female gametes Explanation: Forms zygote. Q.92) What is gene? Answer: Unit of heredity Explanation: Located on chromosomes. Q.93) What is natural selection? Answer: Survival of the fittest Explanation: Individuals with favorable traits survive and reproduce. Q.94) What is a pathogen? Answer: Disease-causing microorganism Explanation: Includes bacteria, viruses, fungi. Q.95) What deficiency causes scurvy? Answer: Vitamin C deficiency Explanation: Leads to bleeding gums and weakness. Q.96) What is vaccination? Answer: Administration of weakened pathogen to develop immunity Explanation: Prevents infectious diseases. Q.97) What are decomposers? Answer: Organisms that break down dead matter Explanation: Example: Bacteria and fungi. Q.98) What is a food web? Answer: Network of interconnected food chains Explanation: Shows complex feeding relationships. Q.99) What is global warming? Answer: Rise in Earth’s average temperature due to greenhouse gases Explanation: Caused mainly by CO₂ increase. Q.100) What is biodiversity? Answer: Variety of living organisms in a region Explanation: High biodiversity ensures ecological stability.