Skip to content

A1.1 - Water (HL)

Paper 1A – Multiple Choice

Question 1

Answer: A


🧠 Big Brain Explanation:

This term links water’s properties to the possibility of life beyond Earth. For life as we know it, liquid water is essential, and the “Goldilocks zone” defines where this is possible.

✅ A | Defines where a planet could have liquid water. Where conditions are “just right”, not too much and not to little. Like with the Goldilocks story 🌍💧⭐

❌ B | This describes a local ocean environment, not an astronomical zone.

❌ C | Refers to star density in galaxies, not planetary habitability.

❌ D | Refers to impact zones, unrelated to life-supporting conditions.

Answer: D

🧠 Big Brain Explanation:

❌ A | While sunlight is important, the zone is about temperature, not light levels for photosynthesis.

❌ B | This is a benefit, but the defining feature is liquid water possibility.

❌ C | This is the role of a magnetic field or atmosphere, not the Goldilocks zone.

✅ D | The Goldilocks zone is defined by the distance from a star where temperatures allow liquid water to exist — the key requirement for life 💧🪐🔥

Answer: D

🧠 Big Brain Explanation:

✅ I | Essential for life. Water dissolves nutrients, helps with chemical reactions, and makes up living cells. 

✅ II | Also essential. Temperature keeps water liquid. Gravity holds the atmosphere so we can breathe and water doesn’t float away into space.

✅ III | Crucial for protection. A magnetic field acts like a shield against harmful radiation from the sun, which would otherwise strip away the atmosphere and damage living cells.

All three are scientifically considered necessary for a planet to support and sustain life  🌍🛡️💧

Answer: C

🧠 Big Brain Explanation:

❌ A | Early Earth was too hot for large underground water reservoirs at that time.

❌ B | There was likely no surface ice before water arrived.

✅ C | This theory suggests that icy asteroids from the outer solar system collided with Earth, delivering water ☄️💧🌎

❌ D | Volcanic outgassing contributed some water, but the asteroid theory specifically involves delivery from space.

Answer: B

🧠 Big Brain Explanation:

❌ A | Asteroids don’t have significant atmospheres; this detection is not feasible or relevant.

✅ B | Matching ratios of hydrogen (e.g., deuterium/hydrogen) and oxygen isotopes between Earth’s water and certain asteroids provide strong evidence they share a common origin 🔬💧☄️

❌ C | Some asteroids may outgas, but this isn’t direct evidence for past delivery to Earth.

❌ D | Simulations show it’s possible, but they don’t provide empirical evidence that it actually happened.

Paper 2 – Short & Long Answer

Question 1