25 free Science MCQs written in the Olympiad exam pattern, each with a step-by-step solution. Tap an option for instant feedback — no sign-up, no ads.
Revise with smart repetition →✍️ These are original practice questions written in the Olympiad pattern for school Olympiad exams — not questions from any official past paper.
Q1. Which planet is known as the 'Red Planet'?
B. Mars — Mars is called the Red Planet because iron-oxide (rust) on its surface gives it a reddish colour.
Q2. The number of bones in the adult human body is:
B. 206 — An adult human has 206 bones. A newborn baby has around 300, some of which fuse together during growth.
Q3. The hardest naturally occurring substance is:
C. Diamond — Diamond, a form of carbon, is the hardest naturally occurring substance (10 on the Mohs scale).
Q4. The 'powerhouse of the cell', where energy is produced, is the:
C. Mitochondrion — The mitochondrion is called the powerhouse of the cell because it produces most of the cell's energy (ATP) through respiration.
Q5. At sea level, pure water boils at a temperature of:
C. 100 °C — At sea level (1 atmosphere pressure), pure water boils at 100 °C and freezes at 0 °C.
Q6. The gas essential for human respiration, taken in when we breathe, is:
C. Oxygen — We breathe in oxygen, which cells use in respiration to release energy, and breathe out carbon dioxide as a waste product.
Q7. The Sun rises in the:
C. East — Because the Earth rotates from west to east, the Sun appears to rise in the east and set in the west.
Q8. Which organ pumps blood around the human body?
B. Heart — The heart is a muscular pump that circulates blood through the body. The lungs add oxygen to the blood, but the heart does the pumping.
Q9. The largest planet in our solar system is:
C. Jupiter — Jupiter is the largest planet — more than 1,300 Earths could fit inside it. Saturn is the second largest.
Q10. Which of these materials is attracted by a magnet?
C. Iron — Iron is a magnetic material and is strongly attracted by magnets. Wood, plastic and glass are non-magnetic.
Q11. Green plants prepare their own food using sunlight, water and carbon dioxide. What is this process called?
D. Photosynthesis — Photosynthesis is the process by which green plants use sunlight, water and carbon dioxide to make food (glucose) and release oxygen.
Q12. Which gas is present in the largest amount in the air around us?
A. Nitrogen — Nitrogen makes up about 78% of the atmosphere, far more than oxygen (about 21%), making it the most abundant gas in air.
Q13. A see-saw in a park is a common example of which simple machine?
B. Lever — A see-saw turns about a fixed point (the pivot or fulcrum), which is the defining feature of a lever.
Q14. Astronauts on the Moon cannot hear each other directly even when standing close. This is because sound cannot travel through a:
D. Vacuum — Sound needs a material medium (solid, liquid or gas) to travel. The Moon has almost no air, so in this near-vacuum sound cannot travel.
Q15. A person whose diet lacks vitamin C is most likely to suffer from which disease?
B. Scurvy — Scurvy, marked by bleeding gums and weakness, is caused by a lack of vitamin C, which is found in citrus fruits and amla.
Q16. A solid object placed in water will sink if its density is:
C. Greater than that of water — An object sinks when it is denser than water; if its density is less than water it floats, and if equal it stays suspended.
Q17. Blue litmus paper turns red when it is dipped into which of the following?
B. Lemon juice — Lemon juice is acidic (it contains citric acid), and acids turn blue litmus red. Soap is basic, while sugar and salt solutions are roughly neutral.
Q18. Which type of blood cell mainly protects the body by fighting germs and infections?
C. White blood cells — White blood cells (WBCs) defend the body against disease-causing germs. Red blood cells carry oxygen and platelets help in clotting.
Q19. Which of the following is a renewable source of energy?
D. Solar energy — Solar energy is renewable because sunlight is naturally replenished, whereas coal, petroleum and natural gas are fossil fuels that will run out.
Q20. You want a mug that keeps hot milk warm for the longest time. Which mug should you choose?
C. A plastic mug — Plastic is a poor conductor of heat (an insulator), so it lets heat escape slowly and keeps the milk warm longer than metal mugs, which conduct heat away quickly.
Q21. A small body that moves around a planet in a fixed path is called a:
B. Satellite — A satellite revolves around a planet; for example, the Moon is a natural satellite that revolves around Earth.
Q22. Which part of a plant is mainly responsible for absorbing water and minerals from the soil?
A. Root — Roots have tiny root hairs that absorb water and dissolved minerals from the soil and anchor the plant.
Q23. Why do we feel cool when sweat evaporates from our skin on a hot day?
C. Evaporation absorbs heat from the body — To change from liquid to vapour, sweat takes heat energy from the skin. This removal of heat lowers the skin's temperature, so we feel cool.
Q24. Which of these animals is a mammal that lays eggs instead of giving birth to young ones?
D. Platypus — The platypus is an egg-laying mammal (a monotreme). Kangaroos, whales and bats are all mammals that give birth to live young.
Q25. During the water cycle, water vapour in the air cools and changes into tiny water droplets that form clouds. This change of state is called:
B. Condensation — Condensation is the change from gas (water vapour) to liquid (water droplets) as it cools, which is how clouds form.
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