Science Olympiad : General Science MCQ practice with Answers set
Q. Earth & Environment : Weather Instruments : Physics : Chemistry : : Space Science : Biology : Scientists : Materials : Gases
Q. What layer of Earth protects us from ultraviolet radiation and harmful solar rays ?
Ans: Ozone layer
Explanation: The ozone layer is found in the stratosphere. It absorbs almost all harmful ultraviolet (UV) rays from the Sun. Without this protective layer, UV radiation would damage human skin, plants, animals, and disrupt life on Earth.
Q. What device is used to measure atmospheric pressure ?
Ans: Barometer
Explanation: A barometer records atmospheric pressure, helping predict weather changes. High pressure means clear weather, while low pressure indicates rain or storms. It is an essential instrument for meteorologists.
Q. Which gas is commonly used in fluorescent lamps for lighting ?
Ans: Mercury vapor
Explanation: Fluorescent lamps contain mercury vapor. When electricity passes through it, the vapor produces ultraviolet light, which then strikes the phosphor coating inside the tube to create bright visible light.
Q. What is the chemical formula for baking soda ?
Ans: Sodium bicarbonate (NaHCO₃)
Explanation: Baking soda is sodium bicarbonate. It produces carbon dioxide gas when heated or mixed with acids like vinegar, which makes dough rise and become fluffy.
Q. Which moon is Earth's only natural satellite ?
Ans: The Moon
Explanation: The Moon orbits Earth and is its only natural satellite. It affects ocean tides, stabilizes Earth’s rotation, and reflects sunlight, making it shine at night.
Q. Which process converts nitrogen gas into a form usable by plants ?
Ans: Nitrogen fixation
Explanation: Nitrogen fixation changes atmospheric nitrogen (N₂) into nitrates or ammonia. Soil bacteria, lightning, and some plants perform this process, making nitrogen available for plant growth.
Q. At approximately what speed does sound travel in air at sea level ?
Ans: 343 m/s
Explanation:
Sound travels around 343 meters per second in air at room temperature. Its speed changes with temperature, humidity, and pressure—faster in warm air, slower in cold air.
Q. Which vitamin is synthesized in the skin when exposed to sunlight ?
Ans: Vitamin D
Explanation: Sunlight triggers the skin to produce Vitamin D. This vitamin helps absorb calcium, strengthens bones, and supports the immune system. Lack of sunlight can cause deficiency.
39. What phenomenon makes the sky appear blue ?
Ans: Rayleigh scattering
Explanation: Rayleigh scattering happens when sunlight hits tiny air molecules. Blue light scatters more than red light because it has a shorter wavelength, making the sky look blue during daytime.
Q. What gas is used to fill balloons to make them float ?
Ans: Helium
Explanation: Helium is lighter than air and non-flammable. Balloons filled with helium float because the gas is less dense than the surrounding atmosphere, lifting the balloon.
Q. What is the term for a substance changing directly from a solid to a gas ?
Ans: Sublimation
Explanation: Sublimation is the direct change of a solid into a gas without passing through the liquid state. Dry ice (solid CO₂) is a common example—it turns straight into gas.
Q. Which instrument is used to measure blood pressure ?
Ans: Sphygmomanometer
Explanation: A sphygmomanometer measures systolic and diastolic blood pressure using an inflatable cuff and gauge. Doctors use it to check heart health and diagnose hypertension.
Q. Who is considered the father of genetics ?
Ans: Gregor Mendel
Explanation: Gregor Mendel studied pea plants and discovered how traits pass from parents to offspring. His work laid the foundation of genetics, involving dominant and recessive genes.
Q. What is the liquid part of human blood called ?
Ans: Plasma
Explanation: Plasma is the straw-colored liquid portion of blood. It transports nutrients, hormones, gases, and waste. It also maintains pH balance and helps in clotting.
Q. What is the hardest natural substance on Earth ?
Ans: Diamond
Explanation: Diamond is extremely hard because its carbon atoms are tightly bonded in a strong crystal structure. It is used in jewelry and for cutting tough materials.
Q. What do plants release during photosynthesis ?
Ans: Oxygen
Explanation: In photosynthesis, plants use sunlight to make food from carbon dioxide and water. Oxygen is released as a by-product, essential for the survival of most living beings.
Q. Which part of the brain controls basic bodily functions like breathing and heartbeat ?
Ans: Medulla oblongata
Explanation: The medulla oblongata controls involuntary functions such as breathing, heartbeat, swallowing, and blood pressure. It is essential for survival and works automatically.
Q. Which organ filters and purifies blood ?
Ans: Kidneys
Explanation: Kidneys remove waste, regulate water and mineral balance, and produce urine. They help maintain blood pressure and keep the body’s internal environment stable.
Q. What type of energy is stored in a stretched rubber band ?
Ans: Potential energy
Explanation: A stretched rubber band stores elastic potential energy. When released, this energy converts into kinetic energy, causing the band to snap back quickly.
Q. What unit is used to measure frequency in physics ?
Ans: Hertz (Hz)
Explanation: Frequency is measured in Hertz, meaning cycles per second. It tells how many times a wave—like sound or electromagnetic waves—repeats in one second.