Hard Science Quiz Questions for Kids (with Answers)
Use this printable quiz list for classroom warm-ups, car trips, or revision. Tap any question to reveal the answer and a short explanation — then play the full science quiz online with hints and stars.
Questions & answers
Tap a question to reveal the answer. 25 questions below.
1. About how fast does light travel?Show answer
- 300,000 km per second — correct
- 150,000 km per second
- 500,000 km per second
- 1,000,000 km per second
Light travels at about 300,000 km per second — the fastest speed possible!
💡 At light speed you could travel around Earth 7.5 times in one second!
2. What does Newton's first law say about moving objects?Show answer
- Things always stop immediately
- Things stay still or keep moving unless a force acts — correct
- Heavy things fall faster
- Every action has no reaction
Newton's first law: objects stay at rest or keep moving in a straight line unless a force changes them!
🚀 In space, astronauts float because there is almost no friction to slow them down!
3. What does DNA carry in every living cell?Show answer
- Water
- Genes — correct
- Sunlight
- Rocks
DNA carries genes — the instructions that tell your body how to grow and work!
🧬 If you stretched out all the DNA in your body, it would reach the Sun and back 600 times!
4. What element has the symbol H on the periodic table?Show answer
- Helium
- Hydrogen — correct
- Hafnium
- Holmium
H stands for hydrogen — the lightest and most common element in the universe!
💧 Hydrogen makes up about 75% of all normal matter in the universe!
5. What is a black hole?Show answer
- A dark planet
- A region where gravity is extremely strong — correct
- An empty hole in space
- A type of moon
A black hole has gravity so strong that not even light can escape from it!
🕳️ The first photo of a black hole was taken in 2019 — it was 55 million light-years away!
6. How do vaccines help protect you from disease?Show answer
- They kill all germs instantly
- They train your immune system — correct
- They replace your blood
- They stop you from eating germs
Vaccines safely teach your immune system to recognise and fight specific diseases!
💉 Vaccines have saved more lives than any other medical invention in history!
7. What is the greenhouse effect?Show answer
- Plants in greenhouses only
- Gases trapping heat in Earth's atmosphere — correct
- The Sun getting hotter every year
- Rain falling inside clouds
The greenhouse effect is when gases like carbon dioxide trap heat and warm the planet!
🌍 Without the natural greenhouse effect, Earth would be about 33°C colder — too cold for most life!
8. Why are mitochondria called the powerhouse of the cell?Show answer
- They store water
- They produce energy for the cell — correct
- They hold the cell's DNA
- They make the cell's walls
Mitochondria convert food into energy that cells need to work!
⚡ Muscle cells can have thousands of mitochondria because they need so much energy!
9. What is the Hubble Space Telescope used for?Show answer
- Measuring earthquakes
- Observing distant objects in space — correct
- Tracking weather on Earth
- Finding oil underground
The Hubble Telescope orbits Earth and captures stunning images of faraway galaxies and stars!
🔭 Hubble has made over 1.5 million observations since it launched in 1990!
10. Who discovered penicillin, the first antibiotic?Show answer
- Marie Curie
- Alexander Fleming — correct
- Louis Pasteur
- Charles Darwin
Alexander Fleming discovered penicillin in 1928 — it became the first antibiotic medicine!
🧫 Fleming's discovery was an accident — mould contaminated his bacteria experiment!
11. Light needs air to travel through space.Show answer
Answer: False
Light does not need air — it travels perfectly through the vacuum of space!
🌌 Light from the Sun crosses 150 million km of empty space to reach Earth!
12. What is the most abundant gas in Earth's atmosphere?Show answer
- Oxygen
- Carbon dioxide
- Nitrogen — correct
- Argon
Nitrogen makes up about 78% of Earth's atmosphere — oxygen is only about 21%!
💨 Although we breathe nitrogen constantly, our bodies cannot use it directly!
13. Approximately how old is Earth?Show answer
- 1.5 billion years
- 2.5 billion years
- 4.5 billion years — correct
- 6.5 billion years
Earth is about 4.5 billion years old — scientists found this by dating ancient rocks!
🌍 If Earth's history were a 24-hour day, humans would appear in the last 2 seconds!
14. What is Marie Curie famous for discovering?Show answer
- Gravity
- Radioactivity — correct
- The telephone
- Penicillin
Marie Curie discovered radioactivity and the elements polonium and radium!
🏆 Marie Curie is the only person to win Nobel Prizes in two different sciences!
15. What do plants make during photosynthesis besides oxygen?Show answer
- Rocks
- Sugar (glucose) — correct
- Metal
- Salt
Photosynthesis makes sugar (glucose) for the plant and releases oxygen as a bonus!
🌱 Plants produce about 170 billion tonnes of sugar through photosynthesis every year!
16. Why do scientists put telescopes in space?Show answer
- Telescopes are too heavy for the ground
- To avoid atmospheric distortion and see clearer — correct
- Because stars only exist in space
- To get closer to the Sun
Space telescopes avoid Earth's blurry atmosphere and capture much clearer images!
🔭 The James Webb Space Telescope can see galaxies from 13 billion years ago!
17. Water is made of two hydrogen atoms and one oxygen atom.Show answer
Answer: True
Water is H2O — two hydrogen atoms bonded to one oxygen atom!
💧 Hot water molecules move faster than cold ones — that is why steam rises!
18. Why do astronauts weigh less on the Moon than on Earth?Show answer
- The Moon has no gravity
- The Moon's gravity is weaker than Earth's — correct
- Astronauts shrink in space
- Their spacesuits are lighter
The Moon is smaller so its gravity is weaker — you would weigh about one-sixth of your Earth weight!
🌙 You could jump six times higher on the Moon than on Earth!
19. What is it called when the Moon blocks the Sun?Show answer
- A lunar eclipse
- A solar eclipse — correct
- A meteor shower
- A comet
A solar eclipse happens when the Moon passes between Earth and the Sun!
🌑 Total solar eclipses last only a few minutes — the longest possible is about 7.5 minutes!
20. What did Galileo discover using his telescope?Show answer
- That Earth is flat
- Moons orbiting Jupiter — correct
- The periodic table
- Penicillin
Galileo discovered four moons of Jupiter — proving not everything orbits Earth!
🔭 Galileo also saw the phases of Venus, which helped prove Earth orbits the Sun!
21. What does the ozone layer protect us from?Show answer
- Rain
- Harmful ultraviolet (UV) rays — correct
- Wind
- Earthquakes
The ozone layer absorbs harmful UV radiation from the Sun that could damage our skin!
🛡️ A single chlorine atom from CFCs can destroy 100,000 ozone molecules!
22. What force did Isaac Newton describe with an apple story?Show answer
- Magnetism
- Gravity — correct
- Electricity
- Friction
Newton described gravity — the force that pulls objects with mass towards each other!
🍎 Newton also invented calculus and the reflecting telescope!
23. Stars twinkle because they are moving back and forth.Show answer
Answer: False
Stars twinkle because Earth's moving atmosphere bends their light — the stars themselves are steady!
✨ Planets do not twinkle much because they are close enough to appear as tiny discs, not points!
24. What material are computer chips mainly made from?Show answer
- Gold
- Silicon — correct
- Iron
- Copper
Computer chips are made from silicon — a element found in sand that can conduct electricity!
💻 A modern chip can contain over 50 billion tiny transistors on a piece smaller than your fingernail!
25. What does the law of conservation of energy state?Show answer
- Energy disappears when used
- Energy cannot be created or destroyed, only changed — correct
- Only plants make energy
- Energy comes only from the Sun
Energy is never lost — it transforms from one type to another, like light to heat!
⚡ When you clap your hands, the motion energy becomes sound and heat energy!
Hard Science Quiz Questions for Kids (with Answers)