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.