General Science — Past Papers — Part 2 MCQs with Explanations

O₃ is the chemical formula of ozone gas . Ozone is an allotrope of oxygen containing three oxygen atoms. It is mainly found in the stratosphere , where it forms the ozone layer . The ozone layer protects Earth from harmful ultraviolet (UV) radiation.

The Sun is the ultimate and main source of energy on Earth. It provides energy through solar radiation (light and heat). All forms of energy on Earth directly or indirectly come from the Sun . It supports life, climate, and ecosystems on Earth. This energy is then converted into various forms, such as : Thermal energy (heat) Kinetic energy (wind, water currents) Electrical energy (generated from solar panels) Chemical energy (fossil fuels, biomass) Biological energy (food chains, ecosystems)

A rectifier is an electrical device that converts Alternating Current (AC) into Direct Current (DC). It allows current to flow in only one direction . It is commonly used in power supplies and chargers . Rectifiers use components like diodes for conversion.

Neptune is the farthest planet. It was visited by the spacecraft Voyager 2 . It's is a very windy place. It has six rings . It has 14 moons .

The audible range of a normal human ear is 20 Hz to 20,000 Hz (20 kHz). Sounds below this range are called infrasound , Sounds above it are called ultrasound . Lower limit: 20 Hz (deep rumbles) Upper limit: 20,000 Hz (high-pitched squeaks) Additional information Adult change: The upper limit often drops to 15,000–17,000 Hz as people get older. Unit of frequency: Hertz (Hz) Last updated 27-07-2026 by NA

The density of gases increases when pressure is increased because gas molecules come closer together . Density is the mass per unit volume of a substance. When pressure increases, the volume of gas decreases (at constant temperature), causing density to increase . This relationship follows Boyle’s Law.

The movement of water from higher water potential to lower water potential is called osmosis . It occurs through a semi-permeable membrane. Only water molecules move in osmosis. It is a passive process (no energy required).

The retina is the light-sensitive layer located at the back of the human eye . It contains special cells called rods and cones that detect light and color. These cells convert light into electrical signals. The signals are then sent to the brain through the optic nerve to produce vision .

The SI unit of electrical resistance is Ohm (Ω). It measures how much a material opposes the flow of electric current. Higher resistance means less current flows. It is defined by V = IR (Ohm’s Law). 1 Ohm = 1 Volt per Ampere.

When white light passes through a prism , it splits into 7 colors , forming a spectrum known as a rainbow : Red Orange Yellow Green Blue Indigo Violet The separation of visible light into its different colours is known as dispersion.

Sublimation is the direct transition of a solid into a gas without passing through the liquid phase. Additional information : Some common sublimating substances: Dry ice (CO₂) – solid → gas Iodine crystals – solid → violet gas Camphor – solid → vapor Naphthalene (mothballs) – solid → gas Ammonium chloride – solid → gas

Mitochondria are called the powerhouse of the cell . Because they produce Adenosine Triphosphate (ATP). ATP is the energy currency of the cell. ATP provides energy for different cellular activities such as movement, growth, and transport. Energy is produced through aerobic cellular respiration using oxygen and الغذائی molecules. They are found in the cytoplasm of most eukaryotic cells. Richard Altmann first described mitochondria in 1890 . Main Parts of a Cell: Cell membrane → Outer protective layer Nucleus → Controls cell activities Cytoplasm → Jelly-like material between membrane and nucleus

Pressure in gases is due to the collision of gas molecules with the walls of the container . Gas molecules are in constant random motion. They continuously strike the container walls. These collisions create force per unit area (pressure). More collisions mean higher pressure.

Photosynthesis produces glucose and oxygen . Green plants use sunlight, water, and carbon dioxide. This process occurs in chloroplasts using chlorophyll . Glucose is used as food for energy and growth . Oxygen is released as a byproduct into the atmosphere.

Short-sightedness is called Myopia . It is corrected by a concave lens . This lens is thin in the center and thick at edges . It helps light focus on the retina correctly. Without correction , distant objects look blurred. Additional information : Long-sightedness is called Hypermetropia . It is corrected by a convex lens . This lens is thick in the center and thin at edges . It helps light focus on the retina properly. Without correction , near objects look blurred.

The largest planet in our solar system is Jupiter. 5th planet 79 known moons (Maximum number of moons) The Great Red Spot is a prominent feature Giant planet and the fastest-rotating planet Rotates approximately once every 10 hours. Age is about 4.603 billion years. Additional information Mercury is the smallest planet of the solar system. ***** Last updated 07-09-2026 by NA

Proteins are called body-building foods. They help in growth, repair of tissues, and muscle development. They are essential for maintaining and rebuilding body cells . They are made of amino acids , the building blocks of the body . Deficiency of protein can lead to weak muscles and poor growth .

Vitamin D is essential for healthy bones . Its deficiency leads to Rickets in children and Osteomalacia in adults . Sunlight is the best natural source of Vitamin D . Additional information : Deficiency effects : Bone pain Weak bones Skeletal deformities Other Vitamin Deficiencies : Vitamin A: Night blindness Vitamin C: Scurvy Vitamin B7 (Biotin): Hair fall

Planet: Uranus Type: Ice Giant Temperature: Around − 224°C ( coldest recorded ) Position from Sun: 7th planet Composition: Hydrogen, helium, methane Discovered: William Herschel in 1781

Carbohydrates are the fastest and main source of energy . They are quickly converted into glucose in the body. Glucose is used immediately for energy production. They provide instant fuel for brain and muscles .

Atoms are made of subatomic particles: protons, neutrons, and electrons. Mass number represents the total number of heavy particles in nucleus. Only protons and neutrons contribute to atomic mass.

Almost all the mass of an atom is concentrated in its nucleus . The nucleus contains protons and neutrons , which are much heavier than electrons . Electrons revolve around the nucleus but contribute very little to atomic mass. The nucleus is located at the center of the atom . Ernest Rutherford discovered the nucleus through the gold foil experiment in 1911 .

Vitamin D is essential for strong bones and teeth . It helps the body absorb calcium and phosphorus . Its deficiency causes Rickets in children. Vitamin D = “ Sunshine vitamin ” Helps in bone mineralization Works with calcium to build strong skeleton

Solar and wind energy are renewable sources of energy, meaning they are sustainable and will not run out. Solar energy is generated from the sun's rays. Wind energy is generated from t he wind.

Our Solar System is located in the Orion Arm of the Milky Way galaxy . It including the Sun and eight planets . It consists of about 100–400 billion stars along with large amounts of gas and cosmic dust . Additional information : The Milky Way is a spiral galaxy with a diameter of about 100,000 light-years. The nearest large galaxy to the Milky Way is Andromeda , located about 2.5 million light-years away.

The Sun is a star at the center of our solar system with a surface temperature of about 6000 °C (Sun’s core is even hotter, ~ 15 million °C ). It provides light and heat , essential for life on Earth. The Sun’s energy drives weather, photosynthesis, and climate .

Sun mass → 1.989 × 10³⁰ kg Earth mass → 5.972 × 10²⁴ kg Sun ≈ 330,000 Earths Sun contains 99.8% of solar system mass Earth is only 0.2% of total system mass (approx.)

Digestion begins in the mouth , starting immediately when food is ingested. Both mechanical digestion (chewing) and chemical digestion (salivary amylase breaking down carbohydrates) Additional information: Mouth : Food is chewed and mixed with saliva that contains enzymes to break down carbohydrates. Esophagus : Food is swallowed and passes through the esophagus into the stomach. Stomach : Food is mixed with stomach acid and enzymes to break down proteins and fats. Small Intestine : Nutrients are absorbed into the bloodstream. Large Intestine : Water and electrolytes are absorbed, and waste is eliminated. **** Last updated by NS on 01 MAY 2026

Composition of Air : Nitrogen → 78% Oxygen → 20.95% Argon → 0.93% Carbon dioxide → 0.04% Other gases → very small traces

Vitamin A is essential for vision, skin health, and immune function . Its deficiency can lead to night blindness (poor ight vision) and other health problems . Additional information : Dry skin and eyes Impaired immune function Poor wound healing Increased risk of respiratory and urinary tract infections

A barometer measures atmospheric (air) pressure . It helps in weather forecasting, detecting storms, and studying climate changes. Two common types of barometers : mercury barometer and aneroid barometer.

Every element is identified by the number of protons in its nucleus. This number determines the identity of the element . It is written as Z in chemistry. It is always equal to the number of electrons in a neutral atom. This is called the atomic number .

Earth water coverage: 71% Land area: 29% Ocean water: 97% of total water Fresh water: 3% of total water Largest ocean: Pacific Ocean

Platelets, also called thrombocytes. They are blood cells that play a vital role in blood clotting. When a blood vessel is injured , platelets aggregate to form a plug that stops the bleeding.

Violet light has the smallest wavelength , approximately 380-450 nanometers (nm). While red light has the longest wavelength , approximately 620-750 nanometers (nm). The order of colors in the spectrum, from longest to shortest wavelength, is: Red, Orange, Yellow, Green, Blue, Indigo, Violet (ROYGBIV).

Conductors are materials that allow electricity to flow through them, such as copper, aluminum, and gold. They have a high concentration of free electrons, which are able to move freely within the material . Additional information: Materials that do not allow electricity to pass through them are called insulators .

The average adult has a blood volume of about 5 liters (5-6 litres) , though this can range from 4.5 to 5.5 liters . Male : About 5.5 liters . Female : About 4.5 liters . Proportion: Blood makes up roughly 7% of a person's total body weight.

Red stars ( Red Dwarfs ) are the coolest stars in the universe. Their surface temperature is around 3000°C ( 5400°F ). Red dwarfs burn their fuel very slowly, lasting trillions of years .

Galileo Galilei is credited with creating his own improved version of the telescope in 1609 . It based on the design of the " Dutch perspective glasses ". He was the first to observe moons of Jupiter, Saturn’s rings, and lunar craters through a telescope.

A black hole is a region of space where matter has collapsed in on itself. It creating an incredibly dense and gravitational field so strong that not even light can escape. Black holes are detected via gravitational effects on nearby stars or X-ray emissions. Famous example : Sagittarius A* at the center of the Milky Way.