Q1. How do plants make their food?
Answer: By Photosynthesis.
Explanation: Plants use sunlight, chlorophyll, carbon dioxide, and water to make glucose (sugar). Oxygen is released in the process.
Q2. Why is our blood red?
Answer: Because of Hemoglobin.
Explanation: Hemoglobin binds with oxygen, and the iron in it gives blood its red color.
Q3. Who discovered electricity?
Answer: Benjamin Franklin made important contributions.
Explanation: In 1752, his kite experiment proved that lightning is a form of electricity.
Q4. Why do seasons change on Earth?
Answer: Due to Earth’s 23.5° tilt and revolution around the Sun.
Explanation: When the Northern Hemisphere tilts toward the Sun, it has summer, while the Southern Hemisphere has winter.
Q5. What is the largest organ in the human body?
Answer: Skin.
Explanation: It covers the body and protects us from germs, sunlight, and injuries.
Q6. Name three methods of purifying water.
Answer:
- Boiling
- Filtration
- Chlorination
Explanation: These methods kill germs and remove impurities, preventing waterborne diseases.
Q7. Why is mercury used in thermometers?
Answer: Because mercury expands and contracts uniformly with temperature.
Explanation: It is a liquid metal with a freezing point of –39°C and a boiling point of 356°C.
Q8. Why does the sky look blue?
Answer: Due to Rayleigh Scattering.
Explanation: Blue light scatters more by air molecules. Red light scatters less, which is why the sky looks reddish during sunrise and sunset.
Q9. Why do humans need oxygen to survive?
Answer: For cellular respiration.
Explanation: Glucose + Oxygen → Energy (ATP) + Carbon dioxide + Water. Oxygen helps release energy for body functions.
Q10. Which poles of a magnet attract and which repel?
Answer:
- Like poles (N–N, S–S) → Repel
- Unlike poles (N–S) → Attract
Explanation: This happens due to the direction of magnetic field lines.
Biology Questions
- Q: What is the basic unit of life?
A: The cell.
Explanation: All living organisms are made up of cells. Cells carry out essential functions such as metabolism, growth, and reproduction. - Q: What is photosynthesis?
A: Photosynthesis is the process by which green plants make their food using sunlight, carbon dioxide, and water.
Explanation: The process produces glucose and oxygen. The general equation is:
6CO2+6H2O+sunlight→C6H12O6+6O26CO_2 + 6H_2O + sunlight → C_6H_{12}O_6 + 6O_26CO2+6H2O+sunlight→C6H12O6+6O2 - Q: Name the organ that pumps blood throughout the body.
A: The heart.
Explanation: The heart is a muscular organ that pumps blood through the circulatory system, supplying oxygen and nutrients to tissues. - Q: What are vaccines used for?
A: Vaccines protect against diseases.
Explanation: Vaccines contain dead or weakened pathogens that stimulate the immune system to produce antibodies without causing the disease. - Q: What is the largest organ in the human body?
A: The skin.
Explanation: Skin protects the body, regulates temperature, and allows the sense of touch.
Physics Questions
- Q: What is the force that pulls objects toward the Earth?
A: Gravity.
Explanation: Gravity is a natural force of attraction between two masses. It gives weight to objects and causes free-falling motion. - Q: What is the speed of light?
A: Approximately 3 × 10^8 m/s.
Explanation: Light travels fastest in a vacuum. Its speed slows down slightly in air or water due to refraction. - Q: What is static electricity?
A: Static electricity is electric charge at rest on a surface.
Explanation: It occurs when electrons are transferred from one object to another, often causing a shock when discharged. - Q: What is energy? Name its types.
A: Energy is the ability to do work.
Explanation: Types include kinetic (motion), potential (stored), thermal, chemical, electrical, and nuclear energy. - Q: What is the unit of force?
A: Newton (N).
Explanation: One Newton is the force required to accelerate 1 kg of mass by 1 m/s².
Chemistry Questions
- Q: What is an element?
A: An element is a pure substance made of only one type of atom.
Explanation: Examples include hydrogen (H), oxygen (O), and gold (Au). - Q: What is the chemical formula of water?
A: H₂O.
Explanation: Water consists of 2 hydrogen atoms and 1 oxygen atom bonded together. - Q: What is the pH scale?
A: The pH scale measures how acidic or basic a substance is.
Explanation: Scale ranges from 0–14. pH < 7 is acidic, pH = 7 is neutral, pH > 7 is basic. - Q: What is rusting?
A: Rusting is the corrosion of iron.
Explanation: Iron reacts with oxygen and moisture to form hydrated iron oxide (rust). - Q: What are acids and bases? Give examples.
A: Acids release H⁺ ions; bases release OH⁻ ions in water.
Explanation: Example of acid: HCl; Example of base: NaOH.
Environmental Science Questions
- Q: What is the greenhouse effect?
A: Trapping of heat by the Earth’s atmosphere.
Explanation: Gases like CO₂, CH₄, and water vapor trap heat, keeping Earth warm. Excessive greenhouse gases cause global warming. - Q: What is recycling?
A: Converting waste into reusable material.
Explanation: Helps reduce pollution, save resources, and conserve energy. - Q: Name the gas essential for breathing.
A: Oxygen (O₂).
Explanation: Humans and animals inhale oxygen for respiration to produce energy. - Q: What is ozone?
A: Ozone is O₃, a gas made of three oxygen atoms.
Explanation: It protects Earth from harmful UV rays in the ozone layer. At ground level, it can be a pollutant. - Q: What is biodiversity?
A: The variety of living organisms in an ecosystem.
Explanation: High biodiversity maintains ecological balance and resilience.
Biology Questions
Q: What is DNA?
A: DNA (Deoxyribonucleic acid) is the molecule that carries genetic information.
Explanation: DNA determines traits and passes hereditary information from parents to offspring.
Q: What are the building blocks of proteins?
A: Amino acids.
Explanation: Proteins are made from long chains of amino acids linked together.
Q: What is respiration?
A: The process of breaking down glucose to release energy.
Explanation: Respiration occurs in cells. Aerobic respiration uses oxygen, while anaerobic does not.
Q: Name the organ that filters blood in humans.
A: The kidney.
Explanation: Kidneys remove waste products and regulate water and salt balance in the body.
Q: What is the function of red blood cells?
A: To carry oxygen.
Explanation: Hemoglobin in red blood cells binds oxygen and transports it to tissues.
Physics Questions
Q: What is work in physics?
A: Work is done when a force is applied to move an object over a distance.
Explanation: Work = Force × Distance (in the direction of force).
Q: What is friction?
A: A force that resists motion between two surfaces in contact.
Explanation: Friction produces heat and slows down moving objects.
Q: What is pressure?
A: Pressure is force per unit area.
Explanation: Formula: Pressure = Force ÷ Area. Unit: Pascal (Pa).
Q: What is sound?
A: Sound is a form of energy that travels in waves through a medium.
Explanation: Sound needs a medium (air, water, solid) to travel and cannot move in a vacuum.
Q: What is momentum?
A: Momentum is the product of mass and velocity of an object.
Explanation: Formula: Momentum = Mass × Velocity.
Chemistry Questions
Q: What is a compound?
A: A substance made from two or more elements chemically combined.
Explanation: Example: H₂O (water), CO₂ (carbon dioxide).
Q: What is an atom?
A: The smallest unit of an element.
Explanation: Atoms consist of protons, neutrons, and electrons.
Q: What is neutralization?
A: A reaction between an acid and a base to form salt and water.
Explanation: Example: HCl + NaOH → NaCl + H₂O.
Q: What are noble gases?
A: A group of inert gases in Group 18 of the periodic table.
Explanation: Examples: Helium, Neon, Argon. They are stable and rarely react.
Q: What is electrolysis?
A: The process of breaking a compound using electricity.
Explanation: Example: Electrolysis of water produces hydrogen and oxygen.
Environmental Science Questions
Q: What is deforestation?
A: Cutting down of forests on a large scale.
Explanation: Leads to habitat loss, soil erosion, and climate change.
Q: What is renewable energy?
A: Energy that comes from natural sources that replenish.
Explanation: Examples: Solar, wind, hydropower, and geothermal energy.
Q: What is composting?
A: The process of decomposing organic waste into fertilizer.
Explanation: It enriches soil and reduces landfill waste.
Q: What is an ecosystem?
A: A community of organisms interacting with each other and their environment.
Explanation: Includes both living (plants, animals) and non-living (air, water, soil) components.
Q: What is sustainable development?
A: Development that meets present needs without harming future generations.
Explanation: Balances economic growth, environmental care, and social equity.
Q: What is mitosis?
A: Mitosis is the process of cell division that produces two identical daughter cells.
Explanation: It helps in growth, repair, and replacement of body cells.
Q: What is meiosis?
A: Meiosis is the process of cell division that produces gametes (sperm and egg cells).
Explanation: It reduces chromosome number by half, ensuring genetic diversity in sexual reproduction.
Q: What is chlorophyll?
A: Chlorophyll is a green pigment found in plants.
Explanation: It absorbs sunlight for photosynthesis.
Q: What is the nervous system?
A: The nervous system controls body functions through electrical signals.
Explanation: It consists of the brain, spinal cord, and nerves.
Q: What are hormones?
A: Hormones are chemical messengers produced by glands.
Explanation: They regulate growth, metabolism, reproduction, and other body functions.
Physics Questions
Q: What is acceleration?
A: Acceleration is the rate of change of velocity.
Explanation: Formula: a=ΔvΔta = \frac{\Delta v}{\Delta t}a=ΔtΔv. Unit: m/s².
Q: State Newton’s First Law of Motion.
A: An object remains at rest or in uniform motion unless acted upon by an external force.
Explanation: Also called the Law of Inertia.
Q: What is refraction of light?
A: The bending of light when it passes from one medium to another.
Explanation: Example: A straw appears bent in water.
Q: What is power in physics?
A: Power is the rate of doing work.
Explanation: Formula: Power = Work ÷ Time. Unit: Watt (W).
Q: What is density?
A: Density is mass per unit volume.
Explanation: Formula: ρ=mV\rho = \frac{m}{V}ρ=Vm.
Chemistry Questions
Q: What is the periodic table?
A: The arrangement of elements in order of increasing atomic number.
Explanation: Elements are grouped by similar properties into periods and groups.
Q: What are isotopes?
A: Atoms of the same element with different numbers of neutrons.
Explanation: Example: Carbon-12 and Carbon-14.
Q: What is valency?
A: The combining capacity of an atom.
Explanation: Example: Oxygen has a valency of 2.
Q: What is an ionic bond?
A: A bond formed by the transfer of electrons.
Explanation: Example: NaCl (sodium chloride).
Q: What is a catalyst?
A: A substance that speeds up a chemical reaction without being consumed.
Explanation: Example: Enzymes in the human body act as catalysts.
Environmental Science Questions
Q: What is global warming?
A: The gradual increase in Earth’s average temperature.
Explanation: Mainly caused by greenhouse gases from burning fossil fuels.
Q: What is afforestation?
A: Planting trees in areas where there were no previous forests.
Explanation: Helps reduce carbon dioxide and improve biodiversity.
Q: What is acid rain?
A: Rain mixed with acidic pollutants like sulfur dioxide and nitrogen oxides.
Explanation: It damages crops, soils, aquatic life, and buildings.
Q: What is a food chain?
A: The sequence of organisms showing who eats whom in an ecosystem.
Explanation: Example: Grass → Grasshopper → Frog → Snake → Eagle.
Q: What is ecological balance?
A: A stable relationship among organisms and their environment.
Explanation: Disruption (like pollution, deforestation) can cause imbalance.