20 Science Quiz Questions With Answers

Science trivia spans everything from distant galaxies to the cells in your body. These twenty questions cover space, biology, chemistry, physics, and Earth science — with answers included so you can learn as you go. For interactive rounds with picture clues and fill-in-the-blank challenges, try the Science quiz on PlayTrivia.

Space & Astronomy

1. What is the closest star to Earth?

Answer: The Sun. Its light takes about eight minutes to reach us.

2. Which planet is known as the Red Planet?

Answer: Mars. Iron oxide on its surface gives it a reddish appearance.

3. What are the four inner planets of the Solar System?

Answer: Mercury, Venus, Earth, and Mars. They are rocky planets closer to the Sun.

4. Which planet has the most moons in our Solar System?

Answer: Saturn. It has more than 140 confirmed moons, including Titan.

5. What force keeps planets in orbit around the Sun?

Answer: Gravity. Massive objects attract each other across space.

Biology

6. What is the powerhouse of the cell?

Answer: The mitochondrion. It produces ATP, the cell's main energy molecule.

7. What gas do plants absorb from the atmosphere during photosynthesis?

Answer: Carbon dioxide. Plants use it with water and sunlight to produce glucose.

8. How many chambers does the human heart have?

Answer: Four — two atria and two ventricles.

9. What is the largest organ in the human body?

Answer: The skin. It protects the body and helps regulate temperature.

10. What molecule carries genetic information in most living organisms?

Answer: DNA (deoxyribonucleic acid). It stores the instructions for building and running an organism.

Chemistry

11. What is the chemical symbol for gold?

Answer: Au. It comes from the Latin word "aurum."

12. What are the three states of matter?

Answer: Solid, liquid, and gas. Plasma is sometimes considered a fourth state.

13. What is the most abundant gas in Earth's atmosphere?

Answer: Nitrogen. It makes up about 78% of the air we breathe.

14. What is the pH of pure water?

Answer: 7. It is neutral on the pH scale.

15. Which subatomic particle has a negative charge?

Answer: The electron. Protons are positive and neutrons are neutral.

Physics & Earth Science

16. What unit is used to measure force?

Answer: The newton. One newton is the force needed to accelerate one kilogram at one metre per second squared.

17. What type of rock is formed from cooled magma or lava?

Answer: Igneous rock. Examples include basalt and granite.

18. What scale measures the magnitude of earthquakes?

Answer: The Richter scale (or the moment magnitude scale used today). Both express earthquake strength logarithmically.

19. What layer of Earth's atmosphere contains the ozone layer?

Answer: The stratosphere. Ozone absorbs much of the Sun's harmful ultraviolet radiation.

20. What is the speed of light in a vacuum (approximately)?

Answer: About 299,792 kilometres per second (roughly 186,282 miles per second). It is a fundamental constant in physics.

Go deeper with science trivia

The best science quiz players connect facts across topics — linking chemistry to biology, or physics to astronomy. PlayTrivia's Science category mixes quick picks, open-ended lists, and picture rounds so you practise more than just multiple choice. You can also start a solo quiz and switch categories whenever you want a new challenge.

Ready to test yourself? Play a quiz on PlayTrivia.