General Science — Past Papers — Part 5 MCQs with Explanations

According to the Kinetic Molecular Theory , faster gas particles hit container walls more often. More frequent and stronger collisions increase the pressure. Higher temperature → higher particle speed → higher pressure. Pressure depends on number of collisions of gas molecules with container walls. Unit of gas pressure: Pascal (Pa) .

Freezing is the process by which a liquid changes to a solid . It is the reverse of melting , which is the process by which a solid changes to a liquid .

Respiration (breathing) is mainly controlled automatically by the brain’s respiratory center in the medulla oblongata . Normally, breathing occurs without conscious control, so it is an involuntary process . When a person cannot control breathing voluntarily (e.g., during sleep or unconsciousness), the body automatically continues respiration .

Enamel is the hard , mineralized outer layer of teeth . It protects the inner parts of the tooth from damage and decay. Enamel is the hardest substance in the human body. It is mainly made of calcium phosphate . Additional information : Incisors (8) – used for cutting food Canines (4) – used for tearing food Premolars (8) – help crush and grind food Molars (12) – grind food during chewing Total adult teeth = 32

Digestion specifically means the mechanical and chemical breakdown of food into simpler substances. Mechanical digestion includes chewing and churning, while chemical digestion involves enzymes and acids. Additional information : Main 5 processes of the digestive system: Ingestion – taking food into the body Digestion – mechanical and chemical breakdown of food Absorption – nutrients enter blood through the intestine Assimilation – cells use absorbed nutrients Egestion – removal of undigested waste

The alimentary canal wall is made of four main tissue layers that help in digestion and movement of food. These layers include mucosa, submucosa, muscular layer, and serosa . Secretin is not a tissue layer; it is a digestive hormone released by the small intestine .

The centrosome is a small non-membranous organelle found mainly in animal cells . It plays a key role in cell division (mitosis and meiosis) by organizing the spindle fibers . It contains two centrioles arranged at right angles. The centrosome ensures proper separation of chromosomes during cell division.

The first compound microscope is believed to have been invented around 1590 . It was developed by the Dutch spectacle makers Hans Janssen and his son Zacharias Janssen . Their invention used two lenses to magnify tiny objects . Additional information : Galileo Galilei – 1609 improved the microscope design Robert Hooke – 1665 observed cork cells and wrote Micrographia Antonie van Leeuwenhoek – 1674 discovered microorganisms Joseph Jackson Lister – 1830 improved modern compound microscope

The invention of the Lever is attributed to Archimedes . The lever was first described in 260 B.C.E . by Archimedes .

1 kilogram (Kg) = 1000 grams (g) So, 0.2 Kg = 0.2 × 1000 g = 200 g Mass is a measure of matter in an object.

Acceleration is not a base quantity. The base quantities are : Length (L) Mass (M) Time (T)

Thermodynamics studies the relationship between heat, temperature, energy, and work . Additional information : First law : Energy cannot be created or destroyed (Law of energy conservation) Second law : Heat flows from hot to cold spontaneously Third law : Absolute zero cannot be reached Zeroth law : Establishes temperature measurement Applications : Engines, refrigerators, heat pumps, and power plants

The ozone layer protects the Earth from the sun. It is a part of the atmosphere that absorbs most of the harmful ultraviolet light from the sun. It sits in the stratosphere . It is abou t 9 to 18 miles above the Earth. It stops dangerous UV rays from hurting living things. Last updated by NS on 14-8-2026

Conduction is the process of heat transfer through direct contact of molecules . In solids, especially metals, molecules vibrate and pass energy to neighboring molecules. No movement of the substance itself is required ; only energy is transferred.

A thermal conductor is a material that allows heat to pass through it easily. Metals like copper, aluminum, and iron are good thermal conductors. Thermal conduction occurs mainly in solids where particles are closely packed. In contrast, thermal insulators (like wood, plastic, and rubber) resist heat flow.

Green plants use carbon dioxide (CO₂) from the atmosphere to make food via photosynthesis . In photosynthesis, CO₂ + H₂O → Glucose + O₂ (with sunlight and chlorophyll).

The symbol ⁴₂He indicates helium has 2 protons (atomic number = 2) and mass number = 4 . In a neutral atom, the number of electrons = protons , so helium has 2 electrons.

Isotopes are atoms of the same element that have: The same atomic number (Z) → same number of protons Different mass numbers → different number of neutrons This means they behave chemically the same but differ in mass.

The freezing point of water is 0°C ( 32°F ), where water changes from liquid to solid . The melting point is also 0°C , where ice changes from solid to liquid . Freezing and melting are opposite processes occurring at the same temperature.

Liquids have no fixed shape but have a fixed volume . Particles are close together but can slide past each other, allowing the liquid to flow. Additional information : Solid : Are tightly packed and stay in a fixed position Gas : Are widely spaced and move freely in any direction

Glucose is a simple sugar (monosaccharide) and a primary source of energy for cells. Its chemical formula is C6H12O6 . Additional information : Fructose : C6H12O6 (same formula as glucose, different structure) Galactose : C6H12O6 Ribose : C5H10O5 Deoxyribose : C5H10O4 Sucrose ( disaccharide ): C12H22O11

The spleen is not part of the digestive tract ; it is part of the lymphatic system and helps in blood filtration and immune response . Additional information: Main components of human digestive tract : Mouth – ingestion and initial digestion Oesophagus – food passage Stomach – protein digestion Small intestine – nutrient absorption Large intestine / Colon – water absorption and feces formation

Hydrochloric acid (HCl) is produced in the stomach, not the liver. The Right lobe, Hepatocyte, Common bile duct are directly associated with the liver. The liver is involved in bile production, metabolism, and detoxification .

Mitochondria are known as the powerhouse of the cell . They are the site of cellular respiration , where glucose is converted into ATP (energy). Mitochondria have a double membrane and their own DNA and ribosomes . They provide energy for all cell activities.

Filtration is not part of digestion ; it occurs mainly in the kidneys for removing waste from blood. Additional information : Main functions of the digestive system: Ingestion – taking in food Propulsion – swallowing and peristalsis Mechanical processing – chewing and churning Chemical digestion – breaking down molecules with enzymes Absorption – nutrients absorbed into blood or lymph

Chromosomes are thread-like structures inside the nucleus that carry genetic material (DNA). They determine an organism’s hereditary traits. Humans have 46 chromosomes arranged in 23 pairs .

The diaphragm of a microscope controls the amount of light passing through the specimen. In humans, the iris regulates the amount of light entering the eye through the pupil. Additional information: Eyepiece → Lens of eye (focuses image) Stage → Retina (holds specimen/image for observation) Light source → Pupil (allows light to enter) Objective lens → Cornea & Lens (magnifies object)

Remote Sensing is the science of collecting information about the Earth’s surface without direct contact. It is mainly done using satellites equipped with special sensors and cameras in space. These satellites capture images and data used for mapping, weather forecasting, and environmental monitoring .

Wind energy is a form of kinetic energy produced by the movement of air. This moving air rotates the blades of wind turbines or fans to generate electricity. Wind power is an important renewable and clean energy source .

Meteorologists are scientists who study the atmosphere and weather conditions. They forecast tornadoes, hurricanes, floods, and other weather events using satellites, radar, and computer models . Their work helps in early warning systems and disaster management .

Wavelength is the distance between two successive crests or two successive troughs in a transverse wave. It represents one complete cycle of a wave. Additional information : Symbol used: λ (Lambda) SI unit: meter (m) Wave formula: v = fλ Example wavelength values: 1 m, 0.5 m, 10 cm, 500 nm, 700 nm Visible light wavelength range: ~ 400 nm – 700 nm

Meiosis is a special type of cell division that produces four daughter cells from one parent cell. These cells are haploid (n), meaning they contain half the number of chromosomes . Meiosis is essential for sexual reproduction and genetic variation .

Venera-9 was the first spacecraft to land on the surface of Venus . Launched by the Soviet Union in 1975. It was designed to study the Venusian atmosphere and surface. It successfully transmitted data from the planet's surface for 53 minutes before its batteries failed.

An Addition Reaction is a chemical reaction in which two or more substances combine to form a single compound. It is also called a Combination Reaction in basic chemistry. This reaction usually releases heat or energy .

An optical instrument used to measure the properties of visible light is called a Spectroscope. It analyzes the composition and properties of materials based on the light they emit or absorb. It helping us understand the physical and chemical properties of objects in the universe.

Global Positioning System (GPS) is a satellite-based navigation system used to monitor the location and movement of vehicles, ships, and aircraft . Developed by the United States , it provides accurate position, navigation, and timing information worldwide . Widely used in transportation, mapping, military operations, and smartphones .

The telescope was first used for astronomical observations in the early 17th century. Galileo Galilei first used an improved telescope in 1609 to observe planets like Jupiter, Saturn, and Venus . He discovered four large moons of Jupiter (Io, Europa, Ganymede, and Callisto).

Solar panels convert sunlight into electrical energy using special cells . Solar energy is a renewable and clean source of energy . These cells are called photovoltaic (PV) cells because they generate electricity when exposed to light . The technology is based on the photovoltaic effect, discovered in 1839.

Bacteria are prokaryotic organisms, meaning they do not have a true nucleus . Their genetic material (DNA) is not enclosed in a membrane-bound nucleus. Instead, the DNA is present in a region called the nucleoid within the cytoplasm . Therefore, bacterial DNA is found floating in the cytoplasm of the cell. Additional information : In contrast, eukaryotic cells (plants, animals, fungi) have DNA enclosed inside a nucleus .

The molecular structure (double-helix model) of DNA was proposed in 1953 . This model explained how DNA replicates and carries genetic information in living organisms. The discovery was made by James Watson and Francis Crick , two molecular biologists.