Class 9 practice
Class 9 science questions.
Science questions for Class 9, at the level of students aged 12–14, each with its answer and a short explanation. Try each one before opening the answer.
During an experiment, Priya observes a cell organelle containing powerful digestive enzymes capable of breaking down foreign materials and worn-out cell parts. Which organelle is Priya observing?
Level 4 of 5Show the answer
Answer: Lysosome
Lysosomes contain digestive enzymes that break down waste and cellular debris. Because they can digest damaged host cells, they are known as suicide bags.
In December, New Delhi experiences chilly winter weather while Melbourne experiences warm summer weather. What is the fundamental cause of this seasonal difference between the two hemispheres?
Level 4 of 5Show the answer
Answer: Earth's tilted axis of rotation
Earth's axis is tilted at 23.5 degrees. In December, the Southern Hemisphere tilts towards the Sun receiving direct sunlight, while the Northern Hemisphere tilts away.
A goldsmith in Jaipur uses a metallic blowpipe to direct a flame onto metal pieces to melt them. Which zone of the candle flame is the hottest and most suitable for this process?
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Answer: Outermost non-luminous zone
Complete combustion occurs in the outermost non-luminous zone where plenty of oxygen is available. This makes it the hottest part of the flame.
Rohan dips a clean iron nail into blue copper sulphate solution in a beaker. After thirty minutes, he observes a clear change in colour. What colour does the solution turn into, and which new compound forms?
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Answer: Pale green and iron sulphate
Iron is more reactive than copper and displaces it from copper sulphate. The solution turns pale green due to the formation of ferrous (iron) sulphate.
A rectangular block of wood floats in water with two-thirds of its volume submerged. What is the density of the wood in kilograms per cubic metre?
Level 4 of 5Show the answer
Answer: 667 kg/m³
A floating object displaces its own weight in fluid. Since two-thirds of its volume is submerged in water (density 1000 kg/m³), the wood's density is (2/3) × 1000 ≈ 667 kg/m³.
During hot summer days in Nagpur, water stored in porous earthen pots remains refreshingly cool. What scientific principle explains this cooling effect?
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Answer: Evaporation absorbs latent heat of vaporisation
Water seeps through pores and evaporates from the pot surface. It absorbs the latent heat of vaporisation from the remaining water, cooling it.
A stone weighs 18 newtons in air. When completely submerged in a beaker of water, it weighs 14 newtons. What is the buoyant force?
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Answer: 4 newtons
Buoyant force equals the apparent loss of weight in the fluid. Here, 18 newtons minus 14 newtons equals 4 newtons.
A candle is placed beyond the centre of curvature of a concave mirror. What kind of image forms on a screen placed in front of the mirror?
Level 4 of 5Show the answer
Answer: Real, inverted, and diminished
When an object is placed beyond the centre of curvature of a concave mirror, light rays converge between the focus and centre of curvature, creating a real, inverted, and diminished image.
During a total lunar eclipse, the Moon often appears dull reddish. Why does this reddish glow occur?
Level 4 of 5Show the answer
Answer: Earth's atmosphere scatters blue light and refracts red sunlight towards the Moon
Earth's atmosphere scatters shorter blue wavelengths of sunlight away, while longer red wavelengths bend through the atmosphere and reach the Moon's surface inside Earth's shadow.
- True or false?
Sound waves travel faster in humid air than in dry air at the same temperature and pressure.
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Answer: True
Water vapour has a lower molecular mass than oxygen and nitrogen molecules. Humid air is therefore less dense than dry air, which allows sound waves to travel faster through it.
- True or false?
Plant cells carry out cellular respiration continuously throughout both day and night.
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Answer: True
Cellular respiration occurs constantly in all living plant cells to produce energy. Photosynthesis occurs only during daytime in the presence of sunlight.
- Fill in the blank.
Thick-walled blood vessels that carry oxygenated blood away from the heart to body tissues are known as ___. (Clue: starts with 'a')
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Answer: arteries
Arteries transport blood under high pressure away from the heart to various organs, while veins return blood to the heart.
- Fill in the blank.
Sound waves that vibrate at frequencies higher than 20,000 hertz are referred to as ___ waves. (Clue: starts with 'u')
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Answer: ultrasonic
Human hearing spans roughly 20 to 20,000 hertz. Frequencies exceeding 20,000 hertz are termed ultrasonic.
- Fill in the blank.
In a banyan tree, specialized vascular tissue called ___ (clue: starts with 'x') transports water and dissolved minerals from the roots.
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Answer: xylem
Xylem transports water and dissolved minerals upward from roots to shoots, driven mainly by the pull of transpiration.
Which metal is the odd one out in its chemical reaction with dilute hydrochloric acid?
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Answer: Copper
Zinc, magnesium, and iron react with dilute hydrochloric acid to produce hydrogen gas. In contrast, copper is less reactive than hydrogen and does not react with dilute hydrochloric acid.
Which rock is the odd one out based on its geological formation?
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Answer: Limestone
Basalt, granite, and pumice are igneous rocks formed from cooling molten rock. Limestone is a sedimentary rock formed from mineral and organic deposits.
Aarav places thin peelings of red onion leaf in a concentrated sugar solution. Under a microscope, he observes the cell membrane shrinking away from the cell wall. What term describes this specific biological phenomenon?
Level 5 of 5Show the answer
Answer: Plasmolysis
When a plant cell is placed in a hypertonic solution, water leaves the cell via exosmosis. The living protoplast shrinks away from the rigid cell wall, a process called plasmolysis.
Ananya stands 1.5 metres in front of a flat plane mirror. She then walks 50 centimetres backwards, away from the mirror. What is the final distance between Ananya and her image?
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Answer: 4.0 metres
Ananya is now 2.0 metres from the mirror. In a plane mirror, the image forms at an equal distance behind the mirror, making the total distance between Ananya and her image 4.0 metres.
A tabla player tightens the skin of his drum. He then strikes it with greater force than before. How do the pitch and loudness of the sound change?
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Answer: Higher pitch and greater loudness
Tightening the membrane increases its vibrational frequency, raising the pitch. Striking with greater force increases the amplitude of vibration, which increases the sound's loudness.
- True or false?
Iron nails sealed in dry oxygen gas will readily form rust over time.
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Answer: False
Rusting requires both oxygen and moisture to occur. Without water vapor present, iron cannot undergo the chemical reaction that forms hydrated iron oxide.
These questions come from Ado’s question bank and are written with AI help. They are never used in ranked play, so practising them here can’t change anyone’s rank.
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