General Science — Past Papers — Part 7 MCQs with Explanations

Protons and neutrons form the nucleus of an atom. Together, they are called nucleons because they are nuclear particles. Additional information : Nucleons determine the mass of an atom. Isotopes are atoms of the same element with different number of neutrons.

In solids , particles are tightly packed and cannot move freely. Their motion is limited to vibrations around fixed positions. Solids retain definite shape and volume due to limited particle motion.

Sublimation is the process in which a solid directly changes into a gas without passing through a liquid phase. This endothermic phase transition Occurs when a substance absorbs enough energy to overcome intermolecular forces. Deposition : Gas to Solid (the reverse process). Examples: Dry ice, iodine, frost/snow. Last updated on 06-March-2026

Apples contain about 0.3 grams of protein medium-sized fruit. Watermelon : 0.6 grams of protein per cup. Mango : 1.4 grams of protein per cup. Peanuts : 20.5 grams of protein per 100 grams.

A deficiency of sodium can lead to imbalances in fluid volume in the vessels and tissues , resulting in conditions such as: Hyponatremia (low sodium levels in the blood) Fluid retention and swelling Edema (excess fluid in tissues)

An aqueous solution is one where water acts as the solvent, dissolving the solute. This type of solution is common in many chemical reactions and biological processes .

Sublimation is the process by which a solid substance transitions directly into a gas or vapour , without going through the liquid phase, and then condenses back into a solid. Examples include iodine, dry ice, and naphthalene.

Gases do not have a definite shape or volume . They take the shape and volume of the container they are in. Gases can be compressed because the particles are far apart.

Non-luminous objects do not produce their own light ; they are visible because they reflect light from other sources. The Moon is non-luminous ; it reflects sunlight. Luminous objects like the Sun, stars, and fireflies produce their own light.

A translucent object allows some light to travel through it, but scatters or absorbs some of the light, making it semi-transparent. Examples : Frosted glass, wax paper, and tissue paper. Additional information: Transparent : Allows all light to pass through, providing a clear view. Opaque : Does not allow any light to pass through.

When an opaque object moves closer to the light source, the shadow becomes larger . This is because the light rays spread out more , increasing the shadow’s size. Opposite effect: Moving the object away from the light source makes the shadow smaller .

A solar eclipse occurs when the Moon passes between the Sun and Earth , blocking sunlight . It can be total, partial, or annular , depending on the alignment. During a total solar eclipse , the day briefly becomes dark.

Pressure is a fundamental physical quantity that is defined as the force exerted per unit area. It is a measure of the strength of a force acting on a surface. It is typically measured in units such as Pascals (Pa) or pounds per square inch (PSI).

Xylem is the plant tissue responsible for transporting water and minerals from roots → stem → leaves . It consists of continuous tubes made of dead cells for easy water flow. Additional information : Phloem : Transports food (sugars) from leaves to other parts

Scalar quantities are physical quantities that have only magnitude (amount or size) but no direction. Examples of scalar quantities include : Mass Temperature Time Energy Distance

A nucleotide , the building block of DNA and RNA . It consists of three components: A phosphate group (phosphate) A sugar molecule (deoxyribose in DNA and ribose in RNA) One of four nitrogenous bases (Adenine, Guanine, Cytosine, and Thymine in DNA ; Adenine, Guanine, Cytosine, and Uracil in RNA )

Taxonomy is the science of classifying and naming organisms. Helps organize plants, animals, and microorganisms into groups. Based on shared characteristics, genetics, and evolutionary relationships. Developed initially by Carl Linnaeus in the 18th century.

Uracil (U) is not a base found in DNA . Instead, it is found in RNA (ribonucleic acid), where it replaces Thymine (T). The four organic bases found in DNA are: Adenine (A) Cytosine (C) Thymine (T) Guanine (G)

Chromosomes are made up of : Nucleic acid (DNA or RNA) Proteins (histones and non-histone proteins) A chromosome is made up of proteins and DNA organized into genes. Each cell normally contains 23 pairs of chromosomes.

Some organisms feed on dead and decaying organic matter instead of living organisms. These organisms are called saprotrophs . They play an important role in decomposition and nutrient recycling in ecosystems. Examples include fungi, bacteria, and some protists .

In maize (Zea mays), the first structure to emerge from the seed during germination is the radical root. It is also known as the primary root. This root grows downward into the soil, anchoring the seedling and absorbing water and nutrients .

There are four fundamental states of matter: solid, liquid, gas and plasma Solid: Fixed shape and volume; particles tightly packed. Liquid: Fixed volume but takes container's shape; particles close but move . Gas: No fixed shape or volume; particles far apart and move freely. Plasma: Ionized gas, found in stars, lightning; electrically charged.

Transpiration is the process by which plants lose water in the form of vapor from leaves, stems, and flowers. It helps in cooling the plant, nutrient transport, and maintaining water balance. Additional information : Evaporation : Water loss from soil or water surfaces Respiration : Energy release by breaking down sugars Photosynthesis : Production of food using sunlight, CO₂, and water

Chlorophyll is a compound that is called a Chelate . Photosynthesis depends on the presence of chlorophyll for the absorption of light. Additional information : There are about six closely related chlorophylls: chlorophyll a chlorophyll b chlorophyll c chlorophyll d chlorophyll e chlorophyll f

The endosperm is the main storage tissue in maize seeds. It containing nutrients like starch, proteins, and oils. It support the growth of the embryo during germination.

Comets are small celestial bodies made of ice, dust, and rock. When they approach the Sun , they form bright tails of gas and dust . Additional information : Often called “ dirty snowballs ” due to icy composition . Comets follow highly elliptical orbits around the Sun.

Our solar system takes approximately 225 to 230 million Earth years to complete one full orbit around the center of the Milky Way galaxy, A period known as a galactic year or cosmic year. Traveling at about 514,000 mph (828,000 km/h) Given the Sun's age, it has circled the galacti c center about 20 times.

Minor objects with irregular shapes orbiting the Sun are called asteroids, It is also known as a minor planet They are found mainly in the asteroid belt between Mars and Jupiter.

Our Milky Way Galaxy is a barred spiral galaxy Looks like a rotating pinwheel from above or below, with a bright disk and spiral arms. Meaning it has a central bar-shaped structure, extending outwards like a giant pinwheel, with our solar system located on one of these arms

The study of relationships between organisms and their environment is called Ecology . It helps understand how living things interact with each other and with their surroundings. Additional information : Embryology studies development of embryos. Ethology studies animal behavior. Entomology studies insects.

Veins are the blood vessels that carry blood from other parts of the body back to the heart. They have one-way valves that prevent blood from flowing backwards and ensure it keeps moving towards the heart.

The main source of energy in stars is nuclear fusion. It is the process of combining atomic nuclei (usually hydrogen nuclei) to form a heavier nucleus, releasing vast amounts of energy in the process. This energy is what makes stars shine.

The ozone layer is a region within the stratosphere , extending from about 15 to 30 km (9 to 19 miles) above the Earth's surface. It contains a high concentration of ozone (O3) , a molecule made up of three oxygen atoms. The ozone layer plays a crucial role in protecting the Earth from harmful ultraviolet (UV) radiation from the sun, particularly UV-C and UV-B rays.

Studies show that it takes an average of 8 minutes and 20 seconds for sunlight to move from the sun to the earth. Sunlight moves at the speed of light. You can see that the distance of the sun from the earth = 149.6 x 106 km . Photons emitted from the surface of the sun need to traverse the vacuum of the universe to reach our eyes.

Homeostasis is the set of metabolic reactions that maintain the internal environment of an organism, regulating factors. Such as temperature, pH, blood sugar levels, and blood pressure.

The Pakistan Space and Upper Atmosphere Research Commission ( SUPARCO ) was established in 1961 . It was originally formed as a Committee in 1961 and gained Commission status in 1981. The SUPARCO is Pakistan's national space agency and is responsible for the development of space technology and its p eaceful applications in the country. It is headquartered in Islamabad and has technical facilities in Karachi, Lahore, Multan, Quetta, Peshawar and Gilgit.

Carbon dioxide (CO2) is a major greenhouse gas. It responsible for about 65% of the Earth's greenhouse effect.

Opaque objects form sharp and dark shadows because they block all light from passing through, creating a clear and defined shadow.

The telescope is undoubtedly the most important investigative tool in astronomy. A celestial body that revolves around a planet is known as a natural satellite .

Fission is the splitting of a nucleus that releases free neutrons and lighter nuclei. The fission of heavy elements is highly exothermic which releases about 200 million eV compared to burning coal which only gives a few eV.