1. What is the chemical formula of water ?
Water is made up of 2 atoms of hydrogen (H₂) and 1 atom of oxygen (O).
Hence, its chemical formula is H₂O.
2. What is the speed of light in vacuum ?
The speed of light in vacuum is approximately 3 × 10⁸ meters per second (m/s), which is equal to 3 lakh kilometers per second (3×10⁵ km/s).
This is one of the fundamental constants of nature, denoted by the symbol ‘c’.
3. Which is the largest organ in the human body ?
The skin is the largest organ of the human body.
It covers the entire external surface and helps in —
Protecting internal organs, Regulating body temperature, and Sensing touch, heat, and cold.
4. H₂SO₄ is the chemical formula of which acid ?
H₂SO₄ represents Sulphuric acid, a strong acid widely used in industries.
It is known as the “King of Chemicals” because it is used in manufacturing fertilizers, paints, detergents, and batteries.
5. Who discovered electricity ?
Benjamin Franklin is credited with discovering electricity in the 18th century.
He performed his famous kite experiment in 1752, proving that lightning is a form of electrical energy.
6. Which gas makes the Sun shine ?
The Sun shines because hydrogen gas undergoes nuclear fusion in its core —
→ Four hydrogen atoms combine to form one helium atom, releasing a huge amount of light and heat energy.
This process is what makes the Sun glow brilliantly. ☀️
7. Which gas makes the Sun shine ?
The Sun produces energy through a process called nuclear fusion, where hydrogen atoms fuse together to form helium.
This reaction releases a tremendous amount of light and heat energy, which makes the Sun shine.
8. Plants prepare food by which process ?
Plants make their own food through photosynthesis, a process that takes place in the chloroplasts using chlorophyll.
In this process, plants use sunlight, carbon dioxide (CO₂), and water (H₂O) to produce glucose (food) and oxygen (O₂).
9. What is the Sl unit of temperature ?
The SI unit of temperature is Kelvin (K).
It is an absolute scale starting from absolute zero (0 K), the point where particles have minimum thermal motion.
Celsius (°C) is commonly used, but the standard SI unit is Kelvin.
10. What is the full form of DNA ?
DNA (Deoxyribonucleic Acid) is the molecule that carries genetic information in living organisms.
It contains instructions for growth, development, functioning, and reproduction of all known living beings.
11. Red color of blood is due to which pigment ?
The red color of blood comes from hemoglobin, a protein pigment in red blood cells (RBCs).
Hemoglobin contains iron and binds with oxygen, giving blood its bright red color when oxygenated and dark red when deoxygenated.
12. What is the outermost layer of Earth called ?
The Earth’s outermost layer is the crust.
It is a thin, solid layer where we live.
Beneath the crust lies the mantle, followed by the core.
The crust includes continental crust (land) and oceanic crust (beneath oceans).
13. What is the outermost layer of Earth called ?
The Earth’s outermost layer is the crust.
It is a thin, solid layer where we live.
Beneath the crust lies the mantle, followed by the core.
The crust includes continental crust (land) and oceanic crust (beneath oceans).
14. Which is the lightest gas ?
Hydrogen is the lightest and simplest gas in the periodic table.
• It has an atomic mass of 1 u.
• It is lighter than air and highly flammable.
• Hydrogen is widely used in rockets, fuel cells, and industrial processes.
15. SI unit of Energy is
The SI unit of energy is Joule (J).
1 Joule is the energy transferred when a force of 1 Newton moves an object 1 meter in the direction of the force.
Watt is the unit of power, Newton is for force, and Pascal is for pressure.
16. Which planet is called the "Red Planet" ?
Mars is called the Red Planet because its surface is covered with iron oxide (rust), giving it a reddish appearance.
It is the fourth planet from the Sun and is known for its thin atmosphere and dust storms.
17. Device used to measure electric current is -
An Ammeter is an instrument used to measure electric current in a circuit.
• It is always connected in series with the circuit.
• Voltmeter measures voltage, Ohmmeter measures resistance, and Galvanometer detects small currents.
18. Which vitamin is known as Ascorbic Acid ?
Vitamin C, also called Ascorbic Acid, is essential for: i. Boosting immunity ii. Healing wounds
Preventing scurvy (a disease caused by vitamin C deficiency)
It is found in citrus fruits, guava, and vegetables.
19. Who is known as the Father of Genetics ?
Gregor Mendel, an Austrian monk, is called the Father of Genetics because he discovered the basic laws of inheritance through his experiments on pea plants.
He formulated the principles of dominance, segregation, and independent assortment.
20. Which metal is used in making thermometers ?
Mercury is used in thermometers because:
• It remains liquid at room temperature
• It expands uniformly with temperature
• It has a high boiling point and does not wet glass, making readings accurate.
21. Which gas is essential for respiration ?
Oxygen (O₂) is essential for cellular respiration in living organisms.
Cells use oxygen to break down glucose, releasing energy, carbon dioxide, and water.
Without oxygen, most organisms cannot survive.
22. Which metal is liquid at room temperature ?
Mercury (Hg) is the only metal that is liquid at room temperature.
It has a melting point of −38.83 °C.
It is used in thermometers, barometers, and electrical switches due to its liquid state and conductivity.
23. Which part of the human brain controls balance ?
The cerebellum, located at the back of the brain, is responsible for:
Maintaining balance and posture
Coordinating voluntary movements
Controlling muscle tone
It ensures smooth and precise movement of the body.
24. The process of water changing into vapor is called
Evaporation is the process by which water changes from liquid to vapor.
It occurs at the surface of a liquid at any temperature.
Condensation is the opposite (vapor to liquid), sublimation is solid to gas, and fusion is solid to liquid.
25. Which planet is known as the "Morning Star"?
Venus is called the Morning Star because it is very bright and visible in the early morning sky just before sunrise.
It is also called the Evening Star when visible after sunset.
Its brightness is due to thick clouds reflecting sunlight.
26. What is the boiling point of water ?
The boiling point of water at standard atmospheric pressure (1 atm) is 100°C (212°F).
• At this temperature, water changes from liquid to vapor.
• 0°C is the freezing point of water.
27. Which organ purifies blood in the human body ?
The kidneys filter waste products and excess water from the blood to form urine.
They help in removing toxins, maintaining water balance, and regulating electrolytes.
The heart pumps blood, lungs exchange gases, and the liver detoxifies chemicals and produces bile.
28. The ozone layer protects us from
The ozone layer, located in the stratosphere, absorbs harmful ultraviolet (UV) radiation from the Sun.
This prevents skin cancer, cataracts, and other harmful effects on humans and animals.
It does not block infrared, radio, or visible light.
29. Which gas is used in fire extinguishers ?
Carbon dioxide (CO₂) is used in fire extinguishers because it:
Cuts off oxygen supply, which is essential for burning.
Does not damage electrical equipment, making it ideal for electrical and liquid fires.
It works by smothering the flames and cooling the fire area.
30. What is the study of universe called ?
Astronomy is the scientific study of the universe, including stars, planets, galaxies, and other celestial bodies.
Biology is the study of living organisms.
Geology is the study of the Earth.
Astrology is a belief system, not a science, that links celestial movements with human life.
31. The pH value of pure water is-
The pH value of pure water is 7, which is neutral — neither acidic nor basic.
pH < 7 → Acidic solution
pH > 7 → Basic (alkaline) solution
Thus, pure water lies exactly in the middle of the pH scale (0–14).
32. Which instrument is used to measure pressure ?
A barometer is an instrument used to measure atmospheric pressure.
It helps in weather forecasting — falling pressure indicates rain, while rising pressure signals clear weather.
Thermometer → measures temperature
Hygrometer → measures humidity
Ammeter → measures electric current
33. Which vitamin helps in blood clotting ?
Vitamin K plays a vital role in blood clotting by helping produce proteins needed for coagulation.
A deficiency of Vitamin K can lead to excessive bleeding.
It is found in green leafy vegetables, broccoli, and spinach.
34. What is the SI unit of Force ?
The SI unit of force is Newton (N).
• 1 Newton is the force required to accelerate a 1 kg mass by 1 m/s².
• Named after Sir Isaac Newton, who formulated the laws of motion.
• Watt → power, Joule → energy, Pascal → pressure.
35. What is used to disinfect drinking water ?
Chlorine is commonly used to kill harmful bacteria and germs in drinking water.
It helps prevent waterborne diseases like cholera and typhoid.
Only a small amount of chlorine is added to keep the water safe and clean for consumption.
36. Which part of plant performs photosynthesis ?
Leaves are the main sites of photosynthesis in plants.
They contain chlorophyll, a green pigment that absorbs sunlight.
Using carbon dioxide (CO₂) and water (H₂O), leaves produce glucose (food) and oxygen (O₂)
37. Sound through cannot travel
Sound requires a medium (solid, liquid, or gas) to travel because it propagates as vibrations of particles.
In a vacuum, there are no particles, so sound cannot travel.
Sound travels fastest in solids, slower in liquids, and slowest in gases.
38. Which planet has rings around it ?
Saturn is famous for its bright and extensive ring system, made up of ice, rock, and dust particles.
While Jupiter, Uranus, and Neptune also have rings, Saturn’s rings are the most prominent and visible.
39. Which acid is found in lemons ?
Lemons contain citric acid, which gives them their sour taste.
Citric acid is also found in oranges, limes, and other citrus fruits.
It is used in food preservation, beverages, and cleaning products.
40. What is used to measure humidity ?
A hygrometer is an instrument used to measure the amount of moisture (humidity) in the air.
• Barometer → measures atmospheric pressure
• Thermometer → measures temperature
• Rain gauge → measures rainfall
41. Human blood has which metal ?
Iron is present in hemoglobin, the protein in red blood cells that carries oxygen.
Iron binds with oxygen in the lungs and releases it to body tissues.
A deficiency of iron can cause anemia, leading to fatigue and weakness.
42. What is the unit of electric resistance ?
Resistance is measured in Ohms (Ω).
It indicates how much a material opposes the flow of electric current.
Volt → unit of voltage
Ampere → unit of current
Watt → unit of power
43. Which gas do plants release during photosynthesis ?
During photosynthesis, plants use carbon dioxide (CO₂), water (H₂O), and sunlight to produce glucose (food).
Oxygen (O₂) is released as a byproduct into the atmosphere, which is essential for respiration in humans and animals.
44. Which organ secretes insulin hormone ?
The pancreas produces insulin, a hormone that helps regulate blood sugar levels.
Insulin lowers blood glucose by allowing cells to absorb and use sugar for energy.
Dysfunction of the pancreas can lead to diabetes mellitus.
45. The scientific name of human being is -
Homo sapiens is the modern human species.
“Homo” means man, and “sapiens” means wise or intelligent.
Homo erectus and Homo neanderthalensis are earlier human species, and Australopithecus is an ancestor of humans.
46. What is the instrument üsed to measure earthquakes ?
A seismograph is an instrument that detects and records the vibrations of the Earth caused by earthquakes.
• The recorded data is called a seismogram.
• Thermometer → measures temperature
• Barometer → measures atmospheric pressure
• Altimeter → measures altitude
47. Which planet is farthest from the Sun ?
Neptune is the eighth and farthest planet from the Sun in our solar system.
It is known for its deep blue color and strong winds.
Jupiter, Saturn, and Uranus are closer to the Sun than Neptune.
48. Which part of the human eye controls light entry ?
The iris is the colored part of the eye that controls the size of the pupil, thus regulating the amount of light entering the eye.
• Pupil → opening controlled by iris
• Cornea and lens → focus light onto the retina
• Retina → senses light and sends signals to the brain
49. Which chemical is used in photography ?
Silver nitrate (AgNO₃) is used in photography because it is light-sensitive.
It reacts with light to form silver particles, which create the image on photographic film or paper.
Other chemicals listed do not have this light-sensitive property.
50. Which gas is known as laughing gas ?
Nitrous oxide (N₂O) is called laughing gas because it can cause temporary euphoria and laughter when inhaled.
It is commonly used as an anesthetic and pain reliever in dental and medical procedures.
Nitrogen → inert gas
Ammonia → cleaning and chemical uses
51. Which instrument is used to measure altitude ?
An altimeter is an instrument used to measure the height or altitude above sea level.
It is commonly used in aircraft, mountaineering, and hiking.
Barometer → measures atmospheric pressure
Hygrometer → measures humidity
Manometer → measures gas or liquid pressure
52. Which planet is known as Earth's twin ?
Venus is called Earth’s twin because it is similar in size, mass, and density to Earth.
However, Venus has a very thick atmosphere and extremely high surface temperatures, making it inhospitable.
Mars, Mercury, and Jupiter differ significantly in size and composition from Earth.
53. Which gas is known as laughing gas ?
Nitrous oxide (N₂O) is called laughing gas because it can cause temporary euphoria and laughter when inhaled.
It is commonly used as an anesthetic and pain reliever in dental and medical procedures.
Nitrogen → inert gas
Ammonia → cleaning and chemical uses