Author: Muhammad Waqar Khan
Meta
Description: Explore 50 essential everyday
science GK questions with detailed, exam-focused explanations covering physics,
biology, chemistry, and space science.
Introduction
General
Knowledge, particularly in the field of everyday science, forms the backbone of
nearly every major competitive examination conducted around the world. Whether
you are preparing for civil services, banking exams, teaching eligibility
tests, defense recruitment, school-level Olympiads, or simple personal
enrichment, a solid grasp of basic scientific facts consistently gives
candidates an edge over those who rely purely on guesswork.
This resource
is built for students, teachers, exam aspirants, and lifelong learners who want
more than a list of one-line answers. Anyone preparing for UPSC, SSC, banking
exams, railway recruitment, teaching certification tests, or school science
olympiads will find these questions directly relevant, since everyday science
forms a recurring section in nearly all of these tests.
There is an
important distinction between memorizing an answer and actually understanding
it. A memorized fact can be forgotten within days or misapplied when a question
is phrased differently. An understood concept, on the other hand, sticks with
you permanently and allows you to reason through unfamiliar questions on exam
day. That is precisely why this guide goes beyond simple answers and explains
the reasoning, the science, and the real-world relevance behind each fact.
Below, you will
find fifty carefully explained general knowledge questions covering physics,
human biology, chemistry, and space science, organized into clear sections for
easier study and revision.
 |
| 50 Everyday Science General Knowledge Questions Explained |
Section 1:
Physics, Measurement, and the Properties of Matter
Q.No.01 — What
is the density of water?
Answer: Approximately 997 kg/m³ at room temperature (commonly rounded to
1000 kg/m³ or 1 g/cm³ at 4°C).
Explanation: Water's density is not a fixed constant across all conditions; it
changes slightly with temperature and pressure. At exactly 4°C, water reaches
its maximum density of about 1000 kg/m³, which is why the commonly taught
figure in schools is 1000 kg/m³ or 1 g/cm³. At typical room temperature (around
20-25°C), the density is closer to 997 kg/m³, which is the more scientifically
precise figure often used in physics problems.
Quick Fact: This unusual density behavior, where water is densest at 4°C
rather than at its freezing point, is why ice floats instead of sinking,
allowing aquatic life to survive beneath frozen lake surfaces in winter.
Q.No.03 — For a
fixed mass of gas at constant temperature, what happens to pressure if volume
decreases?
Answer: Pressure increases.
Explanation: This principle is known as Boyle's Law, one of the foundational
gas laws in physics and chemistry. It states that for a fixed amount of gas
held at constant temperature, pressure and volume are inversely proportional.
This means that squeezing a gas into a smaller space forces its molecules to
collide with the container walls more frequently, which raises the pressure.
You experience this law every time you pump air into a bicycle tire or use a
syringe.
Exam Tip: Remember Boyle's Law with the formula P₁V₁ = P₂V₂, which
frequently appears in numerical questions in physics and chemistry exams.
Q.No.05 — Which
lens corrects long-sightedness (hyperopia)?
Answer: Convex lens.
Explanation: Long-sightedness, medically known as hyperopia, occurs when the
eyeball is slightly too short, or the cornea is too flat, causing light rays to
focus behind the retina rather than directly on it. A convex lens, which
converges light rays, compensates for this by bending incoming light so it
focuses precisely on the retina. This is the opposite correction needed for
short-sightedness (myopia), which requires a concave lens to diverge light rays
before they enter the eye.
Did You Know? Reading glasses that older adults commonly need are convex lenses,
since presbyopia (age-related farsightedness) develops naturally as the eye's
lens loses flexibility over time.
Q.No.06 — What
is the SI unit of electric charge?
Answer: Coulomb (C).
Explanation: The coulomb is named after French physicist Charles-Augustin de
Coulomb, who conducted pioneering research on electrostatic forces in the late
18th century. One coulomb is defined as the amount of charge transported by a
constant current of one ampere flowing for one second. Since a single electron
carries an extremely tiny charge, one coulomb actually represents the combined
charge of roughly 6.24 × 10¹⁸ electrons, illustrating just how small individual
charge carriers are.
Interesting
Fact: The coulomb is one of several SI
units named after pioneering physicists, alongside the newton, the watt, and
the pascal.
Q.No.11 — What
is the SI unit of pressure?
Answer: Pascal (Pa).
Explanation: Named after French mathematician and physicist Blaise Pascal, one
pascal is defined as one newton of force applied over an area of one square
meter. Because a single pascal represents a very small amount of pressure,
real-world measurements are often expressed in kilopascals (kPa) or even larger
units. Atmospheric pressure at sea level, for instance, is approximately
101,325 pascals, or roughly 101.3 kilopascals.
Quick Fact: Weather forecasts often report atmospheric pressure in
hectopascals (hPa), which is numerically identical to the older unit millibar.
Q.No.16 — Which
gas is traditionally used in refrigerators to cool water?
Answer: Ammonia (in traditional and industrial refrigeration systems).
Explanation: Ammonia has long been used as a refrigerant because it absorbs
large amounts of heat when it evaporates, making it highly efficient at
cooling. It remains common in large industrial and commercial refrigeration
systems, such as those used in food processing plants and ice rinks, because of
its low cost and high efficiency. However, most modern household refrigerators
have shifted to hydrofluorocarbons (HFCs) or increasingly to more
environmentally friendly refrigerants like R-600a (isobutane) due to ammonia's
toxicity and the environmental concerns associated with older refrigerant gases
like CFCs.
Exam Tip: If a question specifically asks about household refrigerators
today rather than industrial systems, the expected modern answer may differ
from the classic textbook answer of ammonia.
Q.No.18 — What
converts chemical energy into electrical energy?
Answer: A battery (electrochemical cell).
Explanation: A battery works through electrochemical reactions occurring
between two electrodes submerged in an electrolyte. As these reactions proceed,
electrons are released at one electrode and absorbed at the other, creating a
flow of electric current when the circuit is completed. This energy conversion
process, from stored chemical potential energy to usable electrical energy,
powers everything from small remote controls to electric vehicles.
Did You Know? The first true battery, called the Voltaic Pile, was invented by
Alessandro Volta in 1800, and the unit of electrical potential, the volt, is
named in his honor.
Q.No.21 — What
type of wave is sound?
Answer: Longitudinal wave.
Explanation: In a longitudinal wave, particles of the medium vibrate parallel
to the direction the wave travels, creating alternating regions of compression
and rarefaction. Sound needs a physical medium, such as air, water, or a solid,
to travel because it relies on the vibration of particles to transmit energy.
This is fundamentally different from transverse waves, like light waves, where
particle vibration occurs perpendicular to the direction of travel.
Quick Fact: Sound travels faster through solids than through air because
particles in solids are packed more tightly together, allowing vibrations to
pass between them more quickly.
Q.No.22 — Which
instrument measures very high temperatures?
Answer: Pyrometer.
Explanation: Pyrometers are specialized instruments designed to measure
extremely high temperatures that would damage or exceed the range of ordinary
thermometers, such as those found in furnaces, kilns, and molten metal
processing. Many pyrometers work by detecting infrared radiation emitted from a
hot object without needing direct physical contact with it, a method known as
optical or radiation pyrometry. This makes them invaluable in industries like
metallurgy and glass manufacturing, where materials often exceed 1000°C.
Interesting
Fact: Modern infrared thermometers used
to check body temperature use a similar non-contact radiation-sensing
principle, just calibrated for a much lower and narrower temperature range.
Q.No.23 — What
is one nanometer equal to?
Answer: One billionth of a meter (10⁻⁹ meters).
Explanation: The nanometer is a unit of length used to measure extremely small
structures, including atoms, molecules, and the wavelengths of visible light.
For context, a typical human hair is roughly 80,000 to 100,000 nanometers wide,
which helps illustrate just how minuscule this unit truly is. Nanometers are
essential in the growing field of nanotechnology, which involves engineering
materials and devices at atomic and molecular scales.
Did You Know? The wavelength of visible light ranges from approximately 380 to
700 nanometers, with violet light at the shorter end and red light at the
longer end of the spectrum.
Q.No.24 — Into
how many colors does white light split when passed through a prism?
Answer: Seven colors.
Explanation: When white light passes through a glass prism, it undergoes
dispersion, a phenomenon where different wavelengths of light bend at slightly
different angles due to varying refractive indices. This separates the light
into a visible spectrum traditionally described as seven colors: violet,
indigo, blue, green, yellow, orange, and red, commonly remembered using the
acronym VIBGYOR. Sir Isaac Newton was the first to demonstrate this phenomenon
systematically in the 17th century, proving that white light is actually a
combination of multiple colors rather than a single pure color.
Exam Tip: This same dispersion principle explains how rainbows form, with
raindrops acting as tiny natural prisms that split sunlight.
Q.No.25 —
Through which medium can sound not travel?
Answer: A vacuum.
Explanation: Because sound is a mechanical wave that requires particles to
vibrate and transmit energy, it cannot travel through a vacuum, which by
definition contains no matter or particles. This is why outer space, which is
largely a vacuum, is completely silent despite dramatic depictions in science
fiction films showing explosions with loud sound effects. Astronauts
communicate in space using radio waves, which are electromagnetic waves capable
of traveling through a vacuum, unlike sound.
Quick Fact: This principle was famously demonstrated using a bell jar
experiment, where a ringing bell becomes progressively quieter and eventually
silent as air is pumped out of a sealed container.
Q.No.26 — What
does CNG stand for?
Answer: Compressed Natural Gas.
Explanation: CNG is primarily composed of methane and is produced by
compressing natural gas to less than 1 percent of its volume at standard
atmospheric pressure. It is widely used as an alternative fuel for vehicles
because it burns more cleanly than petrol or diesel, producing fewer harmful
emissions and lower levels of particulate matter. Many public transportation
fleets and taxis in urban areas have adopted CNG specifically to reduce air
pollution.
Did You Know? CNG is different from LPG, both in composition and storage method,
since CNG remains in a gaseous state under high pressure, while LPG is stored
as a liquid.
Q.No.27 — What
does LPG stand for?
Answer: Liquefied Petroleum Gas.
Explanation: LPG is a mixture primarily made up of propane and butane, which
are byproducts of natural gas processing and petroleum refining. It is stored
under moderate pressure in a liquid state, which allows it to be transported
efficiently in cylinders and tanks, and it converts back into gas form when
released for use in cooking stoves, heaters, and some vehicles. LPG is widely
used as a domestic cooking fuel across many countries due to its portability
and relatively clean combustion compared to solid fuels like wood or coal.
Quick Fact: LPG is odorless in its natural state; the distinctive smell
associated with gas leaks is actually an added chemical called ethyl mercaptan,
included deliberately as a safety measure to help detect leaks.
Q.No.28 — Which
lens is used in cameras to focus an image?
Answer: Convex lens (converging lens).
Explanation: This is a commonly confused point, so it deserves a clear
correction: cameras use convex lenses, not concave lenses, to focus an image. A
convex lens converges parallel light rays entering the camera to a focal point,
forming a real, inverted image on the camera's sensor or film, much like how
the human eye's own lens focuses light onto the retina. Concave lenses, by
contrast, diverge light rays and are used in different applications, such as
correcting short-sightedness or in certain telescope designs.
Exam Tip: If you encounter this question with "concave lens"
listed as the answer, treat it as an error. Convex lenses are the
scientifically accurate answer for standard camera focusing, and this
distinction is frequently tested in exams.
Q.No.32 — What
does oxidation involve in a chemical reaction?
Answer: Loss of electrons.
Explanation: In modern chemistry, oxidation is defined in terms of electron
transfer rather than simply the addition of oxygen, which was the older, more
limited definition. When a substance undergoes oxidation, it loses one or more
electrons, while the substance that gains those electrons undergoes reduction,
a paired process collectively known as a redox (reduction-oxidation) reaction.
This electron-based definition explains a broader range of reactions, including
rusting of iron, combustion, and the reactions occurring inside batteries.
Did You Know? A helpful memory aid for this concept is "OIL RIG,"
meaning Oxidation Is Loss (of electrons) and Reduction Is Gain (of electrons).
Q.No.38 — What
is used in cold countries to melt ice on roads?
Answer: Salt (commonly sodium chloride or calcium chloride).
Explanation: Salt works by lowering the freezing point of water through a
process called freezing point depression, meaning that salted water requires a
lower temperature to freeze compared to pure water. When salt is spread on icy
roads, it dissolves into any available moisture, preventing new ice from
forming and helping existing ice melt at temperatures where plain water would
normally freeze solid. Calcium chloride is sometimes preferred over sodium
chloride in extremely cold conditions because it remains effective at lower
temperatures.
Quick Fact: While effective, road salt can be corrosive to vehicles and
infrastructure and harmful to nearby vegetation, which is why some regions use
alternatives like sand for traction or beet juice-based de-icers.
Q.No.40 — What
is Einstein's famous mass-energy equivalence equation?
Answer: E = mc²
Explanation: This equation, published by Albert Einstein in 1905 as part of his
special theory of relativity, states that energy (E) and mass (m) are
interchangeable, related by the speed of light (c) squared. Because the speed
of light is such an enormous number, even a small amount of mass can
theoretically be converted into an extraordinarily large amount of energy, a
principle that underlies both nuclear power generation and nuclear weapons.
This equation remains one of the most recognized formulas in all of science,
symbolizing the deep connection between matter and energy.
Interesting
Fact: Nuclear power plants generate
electricity by harnessing a tiny fraction of the mass-to-energy conversion
described by this equation during controlled nuclear fission reactions.
Q.No.45 — What
is the speed of light?
Answer: Approximately 300,000 kilometers per second (more precisely,
299,792 km/s in a vacuum).
Explanation: The speed of light in a vacuum is considered a universal constant,
meaning it does not change regardless of the observer's motion or reference
point, a cornerstone principle of Einstein's theory of relativity. This value
is often rounded to 300,000 km/s for general use and calculations, though the
precise figure is closer to 299,792 kilometers per second. Light travels
slightly slower when passing through denser media like water or glass, which is
why it bends, or refracts, when moving between different materials.
Exam Tip: Many exams ask for this figure in different units, so it helps to
also remember it as roughly 3 × 10⁸ meters per second.
Section 2:
Human Body and Biology
Q.No.02 — What
is the lifespan of a red blood cell?
Answer: Approximately 120 days.
Explanation: Red blood cells, also called erythrocytes, are produced in the
bone marrow and are responsible for transporting oxygen from the lungs to
tissues throughout the body using a protein called hemoglobin. Unlike most
cells in the body, mature red blood cells lack a nucleus, which limits their
ability to repair themselves over time and results in their relatively short
lifespan of around 120 days. Once they become worn out, they are broken down
primarily in the spleen and liver, with the body continuously producing new red
blood cells to replace them.
Did You Know? The human body produces roughly two million new red blood cells
every second to maintain a healthy blood supply.
Q.No.04 — What
does a deficiency of Vitamin A cause?
Answer: Night blindness.
Explanation: Vitamin A is essential for producing rhodopsin, a light-sensitive
pigment in the retina that allows the eyes to adjust to low-light conditions.
When Vitamin A levels are insufficient, the retina cannot regenerate rhodopsin
quickly enough, making it difficult to see clearly in dim lighting or darkness,
a condition known as night blindness. If left untreated for extended periods,
severe Vitamin A deficiency can progress to more serious eye conditions,
including xerophthalmia, which can potentially lead to permanent vision damage.
Quick Fact: Foods rich in Vitamin A include carrots, sweet potatoes, spinach,
and liver, making dietary deficiency largely preventable through balanced
nutrition.
Q.No.07 — What
does severe Vitamin D deficiency cause?
Answer: Rickets (in children) and osteomalacia (in adults).
Explanation: Vitamin D plays a critical role in helping the body absorb calcium
and phosphorus from food, both of which are essential for building and
maintaining strong, healthy bones. When Vitamin D levels are severely deficient
over a prolonged period, bones fail to mineralize properly, leading to
softening and weakening of bone structure, which manifests as rickets in
growing children and as osteomalacia in adults. This deficiency was
historically common in regions with limited sunlight exposure, since the body
naturally synthesizes Vitamin D when skin is exposed to sunlight.
Interesting
Fact: Vitamin D is sometimes called the
"sunshine vitamin" because roughly 10 to 15 minutes of sunlight
exposure several times a week can help the body produce adequate amounts
naturally.
Q.No.12 — How
much oxygen does a person consume in a day?
Answer: Estimates vary, but a resting adult breathes in roughly 11,000 to
13,000 liters of air per day, of which the body actually consumes a smaller
fraction as usable oxygen.
Explanation: It's worth clarifying an important distinction here: the volume of
air inhaled per day is not the same as the actual oxygen consumed by the body's
cells, since air is only about 21 percent oxygen and the lungs do not extract
all of it during each breath. The commonly cited trivia figure of around 11,000
liters typically refers to total air volume breathed rather than pure oxygen
absorbed, and actual oxygen consumption depends heavily on factors like
activity level, body size, and metabolic rate. This figure increases
substantially during physical exercise, when breathing rate and depth both rise
to meet the body's higher oxygen demand.
Exam Tip: If this question appears with "11,000 liters" as the
expected answer, it is referring to total air breathed, not pure oxygen
absorbed, a nuance worth mentioning if the exam allows explanatory answers.
Q.No.15 — What
is the average blood volume in an adult?
Answer: Approximately 5 liters.
Explanation: The exact blood volume in an adult varies based on factors such as
body size, sex, and overall health, but 5 liters is commonly cited as the
average figure for a typical adult. Blood performs several essential functions,
including transporting oxygen and nutrients to tissues, removing waste products
like carbon dioxide, regulating body temperature, and supporting immune defense
through white blood cells and antibodies. Blood is composed of plasma, red
blood cells, white blood cells, and platelets, each serving distinct and vital
roles in maintaining the body's overall function.
Quick Fact: Blood makes up approximately 7 to 8 percent of a person's total
body weight.
Q.No.20 — How
many major types of white blood cells are there?
Answer: Five major types.
Explanation: White blood cells, or leukocytes, form a core part of the immune
system and are classified into five main types: neutrophils, lymphocytes,
monocytes, eosinophils, and basophils. Each type has a specialized function;
for example, neutrophils are typically the first responders to bacterial
infections, while lymphocytes, which include T-cells and B-cells, play a
central role in targeting specific pathogens and producing antibodies.
Together, these five types work in a coordinated system to detect, attack, and
remove harmful invaders like bacteria, viruses, and parasites from the body.
Did You Know? Neutrophils are typically the most abundant type of white blood
cell in a healthy adult, making up roughly 55 to 70 percent of the total white
blood cell count.
Q.No.30 — Where
is urine produced?
Answer: Kidneys.
Explanation: The kidneys filter waste products, excess water, and salts from
the bloodstream through millions of tiny functional units called nephrons,
ultimately producing urine as a byproduct of this filtration process. Once
formed, urine travels from the kidneys through the ureters into the bladder,
where it is temporarily stored before being expelled from the body through the
urethra during urination. Beyond waste removal, the kidneys also play a crucial
role in regulating blood pressure, maintaining electrolyte balance, and
producing hormones that stimulate red blood cell production.
Quick Fact: The kidneys filter the entire volume of blood in the human body
roughly 40 times per day.
Q.No.31 — At
night, what do plants intake and release?
Answer: Plants intake oxygen and release carbon dioxide at night.
Explanation: During daylight hours, plants primarily perform photosynthesis,
absorbing carbon dioxide and releasing oxygen as a byproduct. However, plants
also continuously perform cellular respiration, a separate process that
consumes oxygen and releases carbon dioxide, just like animals do, in order to
convert stored sugars into usable energy. During the day, photosynthesis occurs
at a much higher rate than respiration, masking respiration's effects, but at
night, in the absence of sunlight, photosynthesis stops entirely, leaving
respiration as the dominant visible process.
Exam Tip: This is a frequently misunderstood concept; plants perform
respiration all the time, not just at night, but the absence of photosynthesis
after dark makes their oxygen consumption more noticeable.
Q.No.39 — What
is the fluid part of blood called?
Answer: Plasma.
Explanation: Plasma makes up roughly 55 percent of total blood volume and
consists mostly of water, along with dissolved proteins, hormones, nutrients,
and waste products being transported throughout the body. It serves as the
medium through which red blood cells, white blood cells, and platelets are
suspended and carried through the circulatory system. Plasma also plays a
crucial role in blood clotting, thanks to proteins like fibrinogen, and is
often separated from whole blood for medical treatments and transfusions.
Did You Know? Donated plasma can be used to treat patients with severe burns,
clotting disorders, and certain autoimmune conditions, making plasma donation a
valuable contribution to modern medicine.
Q.No.41 — What
device measures blood glucose level?
Answer: A glucose meter, or glucometer.
Explanation: A glucometer is a small, portable medical device that measures the
concentration of glucose in a person's blood, typically using a tiny blood
sample obtained through a finger prick and a disposable test strip. This device
is essential for individuals managing diabetes, allowing them to monitor their
blood sugar levels regularly and make informed decisions about diet,
medication, and insulin dosage. Modern continuous glucose monitors (CGMs) have
also emerged as an advanced alternative, using a small sensor placed under the
skin to track glucose levels throughout the day without repeated finger pricks.
Quick Fact: Normal fasting blood glucose levels typically fall between 70 and
100 milligrams per deciliter (mg/dL) in healthy adults, though exact reference
ranges can vary slightly between laboratories.
Section 3:
Space, Astronomy, and the Solar System
Q.No.08 — Which
is the outermost planet in the solar system?
Answer: Neptune.
Explanation: Neptune holds the title of the outermost planet in our solar
system, a status it gained after Pluto was reclassified as a dwarf planet by
the International Astronomical Union in 2006. Neptune is an ice giant, composed
largely of water, ammonia, and methane ices surrounding a rocky core, and its
striking blue color comes from methane in its atmosphere absorbing red light
while reflecting blue light into space. It takes Neptune approximately 165
Earth years to complete a single orbit around the Sun.
Did You Know? Neptune has the strongest sustained winds of any planet in the
solar system, with speeds recorded at over 2,000 kilometers per hour.
Q.No.09 — How
many planets are there in the Solar System?
Answer: Eight.
Explanation: The eight recognized planets, in order from the Sun, are Mercury,
Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto was considered
the ninth planet until 2006, when the International Astronomical Union
established a formal definition of what qualifies as a planet, a definition
Pluto did not meet because it had not cleared its orbital neighborhood of other
debris. Pluto is now classified as a dwarf planet, alongside similar objects
like Eris, Haumea, Makemake, and Ceres.
Exam Tip: Be prepared for exam questions that specifically ask about this
2006 reclassification, since it remains a popular and frequently tested trivia
point.
Q.No.10 — Which
planet is closest to the Sun?
Answer: Mercury.
Explanation: Mercury orbits the Sun at an average distance of about 58 million
kilometers, making it the closest planet in our solar system. Despite this
proximity, Mercury is not actually the hottest planet, since it lacks a
substantial atmosphere to trap heat, causing dramatic temperature swings
between scorching daytime highs and freezing nighttime lows. Venus, despite
being farther from the Sun, is hotter overall due to its thick atmosphere
trapping heat through an intense greenhouse effect.
Interesting
Fact: A single day on Mercury, meaning
one full rotation on its axis, takes about 59 Earth days, while a year on
Mercury takes only about 88 Earth days.
Q.No.13 — Which
is the most abundant element in the Earth's crust?
Answer: Oxygen.
Explanation: Oxygen makes up approximately 46 percent of the Earth's crust by
mass, primarily existing in combined form within minerals and compounds like
silicates and oxides rather than as free oxygen gas. Silicon is the second most
abundant element in the crust, and together, oxygen and silicon combine to form
silicate minerals, which make up the majority of rocks found on Earth's
surface. It's worth distinguishing this from atmospheric composition, where
nitrogen, not oxygen, is the most abundant gas.
Quick Fact: While oxygen dominates the Earth's crust, iron is the most
abundant element in the Earth as a whole, largely due to the massive
iron-nickel core at the planet's center.
Q.No.14 — Which
is the most abundant element in the universe?
Answer: Hydrogen.
Explanation: Hydrogen accounts for roughly 75 percent of the universe's
elemental mass, making it by far the most abundant element in existence. It
formed in enormous quantities during the early moments after the Big Bang and
serves as the primary fuel for stars, which convert hydrogen into helium
through nuclear fusion, a process that generates the immense energy stars
radiate as light and heat. Helium, formed both during the Big Bang and through
stellar fusion, ranks as the second most abundant element in the universe.
Did You Know? Our own Sun is composed of roughly 70 percent hydrogen and 28
percent helium, with trace amounts of heavier elements making up the remainder.
Q.No.17 — What
is the Sun?
Answer: A star.
Explanation: The Sun is a massive, glowing sphere of hot plasma held together
by its own gravity, classified specifically as a G-type main-sequence star,
sometimes informally called a yellow dwarf. It generates energy through nuclear
fusion in its core, where hydrogen atoms combine under extreme pressure and
temperature to form helium, releasing enormous amounts of energy in the
process. This energy travels outward and eventually reaches Earth as sunlight,
providing the heat and light necessary to sustain nearly all life on our
planet.
Quick Fact: The Sun accounts for approximately 99.8 percent of the total mass
within our entire solar system.
Q.No.19 — Who
discovered radioactivity?
Answer: Henri Becquerel.
Explanation: French physicist Henri Becquerel discovered radioactivity in 1896
while investigating the properties of uranium salts, accidentally finding that
they emitted energy capable of exposing photographic plates even without
exposure to sunlight. This groundbreaking discovery opened the door for further
research by scientists Marie and Pierre Curie, who expanded on Becquerel's work
and coined the term "radioactivity" itself. In recognition of their
combined contributions, Becquerel, Marie Curie, and Pierre Curie jointly
received the Nobel Prize in Physics in 1903.
Did You Know? The SI unit for radioactivity, the becquerel (Bq), is named
directly in his honor.
Q.No.33 — What
does GPS stand for?
Answer: Global Positioning System.
Explanation: GPS is a satellite-based navigation system originally developed by
the United States Department of Defense, now widely used worldwide for civilian
purposes such as vehicle navigation, mapping, and location tracking. It works
by using a network of orbiting satellites that continuously transmit signals to
GPS receivers on Earth, which calculate precise location, speed, and time by
measuring the time delay of signals received from multiple satellites
simultaneously. A minimum of four satellites is typically needed to determine
an accurate three-dimensional position.
Exam Tip: Other countries operate their own similar satellite navigation
systems, including Russia's GLONASS, the European Union's Galileo, and China's
BeiDou, which are sometimes confused with GPS in exam questions.
Q.No.34 — What
kind of orbits do comets generally have?
Answer: Highly elliptical orbits.
Explanation: Unlike planets, which follow relatively circular orbits around the
Sun, comets typically travel in highly elongated, elliptical paths that take
them extremely close to the Sun at one extreme and far out into the outer solar
system at the other. This is why many comets are only visible from Earth once
every several years, decades, or even centuries, depending on the length of
their specific orbital period. As a comet approaches the Sun, solar radiation
causes its icy surface to vaporize, creating the glowing tail that makes comets
so visually striking.
Interesting
Fact: Halley's Comet, one of the most
famous comets, has an orbital period of approximately 76 years and was last
visible from Earth in 1986, with its next appearance expected around 2061.
Q.No.35 — Which
planet moves around the Sun at the highest speed?
Answer: Mercury.
Explanation: Mercury travels around the Sun at an average orbital speed of
about 47 kilometers per second, making it the fastest-moving planet in our
solar system. This high speed is a direct consequence of its proximity to the
Sun, since the Sun's gravitational pull is significantly stronger at shorter
distances, requiring closer planets to orbit faster to maintain a stable path.
As a general rule, planets located farther from the Sun move progressively
slower in their orbits.
Quick Fact: Neptune, the outermost planet, orbits at a comparatively sluggish
speed of about 5.4 kilometers per second.
Q.No.36 — Which
planet is nearest to the Earth?
Answer: Venus, on average.
Explanation: While Mars is often assumed to be Earth's closest planetary
neighbor due to popular culture and space exploration coverage, Venus is
actually closer to Earth on average, with a typical distance of about 41
million kilometers compared to Mars's average distance of roughly 78 million
kilometers. Interestingly, a 2019 mathematical analysis using average orbital
positions over time suggested that Mercury may actually be, on average, the
closest planet to every other planet in the solar system, including Earth, due
to how orbital geometry works over long periods. For most standard exam
purposes, however, Venus remains the accepted answer as Earth's nearest
planetary neighbor.
Exam Tip: If a question specifies "closest at any given time"
versus "closest on average over time," the expected answer may
differ, so read the question phrasing carefully.
Q.No.37 — Which
planet has the shortest orbital period around the Sun?
Answer: Mercury.
Explanation: Mercury completes one full orbit around the Sun in just about 88
Earth days, the shortest orbital period of any planet in our solar system. This
short year is a direct result of Mercury's close distance to the Sun, since
orbital period depends on both distance and the Sun's gravitational influence,
meaning closer planets complete their orbits much faster than those farther
away. This relationship between distance and orbital period is described
mathematically by Kepler's Third Law of Planetary Motion.
Did You Know? Despite having the shortest year, Mercury has one of the longest
days relative to its year, since it rotates very slowly on its axis compared to
how quickly it orbits the Sun.
Q.No.42 — What
is the estimated age of the Universe?
Answer: Approximately 13.8 billion years old.
Explanation: Scientists estimate the age of the universe primarily by studying
the cosmic microwave background radiation, a faint afterglow of heat left over
from the Big Bang, combined with observations of the universe's current rate of
expansion. This estimate of 13.8 billion years comes from detailed data
collected by space missions such as the Planck satellite, which has
significantly refined earlier estimates made using less precise instruments.
The Big Bang theory remains the leading scientific explanation for the
universe's origin, supported by multiple independent lines of evidence.
Quick Fact: By comparison, our own solar system is estimated to be about 4.6
billion years old, meaning the universe existed for roughly 9 billion years
before our Sun and planets even formed.
Q.No.43 — How
many planets are visible to the naked eye without a telescope?
Answer: Five.
Explanation: Mercury, Venus, Mars, Jupiter, and Saturn are all visible to the
naked eye under suitable viewing conditions, a fact that has allowed humans to
observe and track these planets since ancient times, long before the invention
of telescopes. Uranus is technically visible under extremely dark skies with
excellent eyesight, but it is so faint that it is not typically considered
practically visible without optical aid, and Neptune is never visible without a
telescope. This is why ancient astronomers across many civilizations were aware
of these five planets thousands of years before modern astronomy developed.
Interesting
Fact: Venus is often called the
"Evening Star" or "Morning Star" because of its brilliant
brightness in the sky, even though it is a planet, not a star.
Q.No.44 — Which
planet is called the "bodyguard of the Earth"?
Answer: Jupiter.
Explanation: Jupiter's immense size and powerful gravitational field allow it
to attract and capture many comets and asteroids that might otherwise be on a
collision course with the inner solar system, including Earth. This protective
gravitational effect has led scientists to nickname Jupiter the
"bodyguard" or "shield" of the solar system's inner
planets, though the extent of this protective role has been debated and refined
in more recent astronomical research. Some studies suggest Jupiter's influence
is more complex than originally thought, occasionally redirecting objects
toward the inner solar system rather than only away from it.
Did You Know? One of the most dramatic demonstrations of Jupiter's gravitational
influence occurred in 1994, when the Shoemaker-Levy 9 comet collided directly
with Jupiter, an event closely observed by astronomers worldwide.
Q.No.46 — On
which planet is the Great Red Spot located?
Answer: Jupiter.
Explanation: The Great Red Spot is a massive, persistent storm system in
Jupiter's atmosphere, large enough that it could comfortably fit more than one
Earth within its boundaries, though recent observations show it has been
gradually shrinking over the past several decades. This storm has been
continuously observed for at least 150 years, and possibly much longer, making
it one of the most enduring weather phenomena known in the solar system. Its
reddish color is believed to result from complex chemical reactions involving
compounds exposed to sunlight in Jupiter's upper atmosphere, though the exact
chemistry is still studied by scientists today.
Quick Fact: Wind speeds within the Great Red Spot have been measured at over
400 kilometers per hour.
Q.No.47 — Which
planet is easily visible from the Earth?
Answer: Venus.
Explanation: Venus is the brightest planet visible from Earth, thanks to its
thick, highly reflective cloud cover that bounces sunlight back efficiently,
combined with its relatively close distance to Earth. It is often visible
shortly after sunset or before sunrise, earning it the popular nicknames
"Evening Star" and "Morning Star," even though it is a
planet rather than a star. Its brightness has made it one of the most
recognizable objects in the night sky throughout human history, referenced in
the mythology and astronomy of numerous ancient cultures.
Exam Tip: Don't confuse this with Sirius, which is the brightest star (not
planet) visible in Earth's night sky.
Section 4:
Chemistry, Earth Science, and Everyday Facts
Q.No.29 — Which
is the densest naturally occurring substance on Earth?
Answer: Osmium.
Explanation: Osmium is a hard, brittle, bluish-white metal belonging to the
platinum group of elements, and it holds the distinction of being the densest
naturally occurring element on Earth, with a density of approximately 22.6
grams per cubic centimeter. Due to its extreme hardness and density, osmium is
rarely used in pure form and is instead typically alloyed with other metals for
applications requiring exceptional durability, such as fountain pen tips,
electrical contacts, and certain specialized instruments. Iridium, another
platinum-group metal, has a very similar density and is sometimes cited as a
close second.
Quick Fact: Despite its impressive density, osmium is quite brittle and can
shatter under stress, making it unsuitable for many structural applications
despite its remarkable weight for its size.
Q.No.48 — What
is the approximate salinity percentage of ocean water?
Answer: Approximately 3.5 percent.
Explanation: Ocean salinity refers to the concentration of dissolved salts,
primarily sodium chloride, in seawater, and this concentration remains
relatively consistent across most of the world's oceans, though it can vary
slightly by region due to factors like evaporation rates, precipitation, and
freshwater river inflow. This salt content originates from the gradual
weathering of rocks on land, which releases minerals that rivers carry into the
ocean over millions of years, combined with mineral-rich discharge from underwater
volcanic activity. Areas near river mouths tend to have lower salinity due to
freshwater dilution, while enclosed seas with high evaporation rates, like the
Red Sea, tend to have higher salinity levels.
Did You Know? The Dead Sea, despite its name suggesting an ocean connection, is
actually a landlocked lake with a salinity level of roughly 34 percent, nearly
ten times saltier than typical ocean water, which is why objects float so
easily on its surface.
Q.No.49 — What
determines an element's position in the periodic table?
Answer: Its atomic number, which represents the number of protons in the
nucleus of an atom.
Explanation: This is an important correction to make clearly: elements are
arranged in the periodic table according to their atomic number, meaning the
number of protons found in the nucleus, not the number of electrons, as is
sometimes mistakenly stated. While a neutral atom does have an equal number of
protons and electrons, ions (charged atoms) have unequal numbers of electrons
relative to protons, yet their position on the periodic table remains fixed
based on the unchanging proton count. This modern arrangement, developed as an
evolution of Dmitri Mendeleev's original 19th-century periodic table, groups
elements with similar chemical properties into vertical columns called groups.
Exam Tip: Remember clearly: atomic number = number of protons, not
electrons. This distinction is commonly tested and easy to get wrong if rushed.
Q.No.50 — In
which direction does Earth rotate?
Answer: Counterclockwise when viewed from above the North Pole, resulting
in the Sun appearing to rise in the east and set in the west.
Explanation: Earth rotates on its axis from west to east, which is why the Sun,
Moon, and stars all appear to move across our sky from east to west, even
though it is actually the Earth turning beneath them, not the sky moving around
us. Viewed from a vantage point directly above the North Pole, this rotation
appears counterclockwise, while from above the South Pole, the same rotation
would appear clockwise, since perspective reverses the apparent direction. This
single rotation takes approximately 23 hours, 56 minutes, and 4 seconds to
complete, which is very slightly shorter than the 24-hour day we use in daily
life, a difference accounted for by the distinction between a solar day and a
sidereal day.
Interesting
Fact: Earth's rotation is gradually
slowing down over extremely long timescales due to tidal friction caused by the
Moon's gravitational pull, lengthening our days by a tiny fraction of a second
roughly every century.
Key Takeaways
- Everyday
science questions frequently tested in competitive exams span physics,
biology, chemistry, and astronomy, and understanding the reasoning behind
each answer builds long-term retention far better than memorization alone.
- Several
classic trivia answers require careful nuance, such as cameras using
convex lenses (not concave), and atomic number being determined by protons
(not electrons), both common points of confusion worth double-checking.
- Basic
physical laws like Boyle's Law and Einstein's mass-energy equivalence
appear repeatedly across different exam formats, so understanding the
underlying principle allows you to answer varied phrasings of the same
core concept.
- Space and
astronomy questions often rely on comparative reasoning, such as
understanding why Mercury is both the fastest-orbiting and closest planet
to the Sun, rather than isolated memorized facts.
- Human
biology questions, including blood composition, vitamin deficiencies, and
organ functions, connect directly to practical health knowledge that
extends well beyond exam preparation.
Frequently
Asked Questions
1. Why is
everyday science given so much importance in competitive exams? Everyday science tests a candidate's practical understanding of
the world around them, rather than purely theoretical or specialized knowledge.
Since it draws from real, observable phenomena, it is considered a fair and
widely accessible section that rewards curiosity and logical reasoning
alongside memorization.
2. Is it better
to memorize these answers or understand the concepts? Understanding concepts is significantly more effective for
long-term exam success. Memorized facts can be forgotten or misapplied when
questions are rephrased, while a genuine understanding of underlying principles
allows you to confidently answer variations of the same question.
3. Which exams
commonly include these types of questions?
These questions frequently appear in UPSC civil services exams, SSC (Staff
Selection Commission) exams, banking sector recruitment tests, railway
recruitment exams, teaching eligibility tests, defense service exams, and
school-level science olympiads across many countries.
4. Are there
any commonly repeated errors in traditional GK question sets? Yes, a few recurring errors exist in older or less carefully
edited GK materials, such as incorrectly stating that cameras use concave
lenses (the correct answer is convex) or that atomic number is based on
electron count (the correct basis is proton count). Always cross-check facts
against updated, reliable scientific sources.
5. How often
should I revise these general science facts? Regularly
spaced revision, ideally reviewing material every few days initially and then
gradually extending the interval, has been shown to improve long-term retention
far more effectively than last-minute cramming before an exam.
6. Do
scientific facts like these ever change over time? Yes, scientific understanding evolves as new research and more
precise instruments become available. For example, Pluto's reclassification
from a planet to a dwarf planet in 2006 is a clear case of a fact changing due
to updated scientific criteria.
7. Why do some
sources give slightly different numerical answers for the same fact? Minor variations often occur due to rounding, measurement
precision, or differing scientific conventions, such as water's density being
cited as either 997 kg/m³ or 1000 kg/m³ depending on the specific temperature
referenced.
Conclusion
Building a
strong foundation in everyday science is not simply about passing an exam; it
is about developing a genuine, functional understanding of how the natural
world operates around you every single day. From the physics governing why ice
floats to the biology explaining how your blood carries oxygen, these fifty
concepts represent essential building blocks of scientific literacy that extend
well beyond any single test or certification.
As you continue
your preparation, focus on understanding the reasoning behind each answer
rather than treating this list as something to memorize and forget. Revisit
challenging concepts periodically, connect them to real-world observations
whenever possible, and don't hesitate to explore any topic in greater depth if
it sparks your curiosity. This approach will serve you well, not only in your
upcoming exams but throughout your broader academic and professional journey.
Trusted
References & Sources
- International
Astronomical Union (IAU), official planetary classification resolutions
(2006)
- NASA Solar
System Exploration educational resources
- National
Institutes of Health (NIH), human physiology and vitamin deficiency
resources
- Encyclopaedia
Britannica, physics and chemistry reference entries
- World
Meteorological Organization, atmospheric pressure and measurement
standards
This article has been prepared and reviewed for factual accuracy as an educational reference resource. Readers preparing for formal examinations are encouraged to cross-verify specific figures against their exam's official syllabus and current reference materials, as scientific consensus and measurement standards can be periodically updated.
Related Articles
Top 30 General Knowledge Questions
and Answers for All Exams (2026 Edition)
Top 30 General Knowledge Questions
and Answers for Competitive Exams (2026 Edition)
Top 30 General Knowledge Questions
with Expert Explanations
100 Years of Facts in 50 Questions:
The Ultimate General Knowledge Guide for Competitive Exams
50 Everyday Science Facts Every
Student Should Know: Earth, Biology & Rocks Explained
Everyday Science Made Simple: 50
Essential GK Questions on Rocks, Light & Human Digestion
50 Essential Human Body GK Questions
& Answers: Digestive and Circulatory Systems Explained
50 Must-Know GK Questions on the
Human Heart and Blood: Complete Guide with Explanations
Current Affairs Quiz – 21 April 2021
| 6 Important GK Questions with Answers
 |
| Author |
0 Comments