Water Cycle Quiz: Test Yourself

Try all ten questions before you look at the answers. Questions 1 to 7 are multiple choice; questions 8 to 10 need a short written answer, so write a sentence or two, not just one word. The answers are printed upside down at the foot of the infographic. The worked answers below explain why each answer is right, which is where most of the learning happens.

Answer: B, evaporation. Evaporation is the change from liquid water to water vapour, a gas. Heat gives water molecules enough energy to break away from the liquid. It happens fastest at boiling point but also at much lower temperatures, more slowly. Condensation is the opposite change, from vapour back to liquid.

Answer: A, transpiration. Plants take up water through their roots, move it through the plant, and release water vapour from their leaves through tiny pores called stomata. Scientists often add transpiration and evaporation from land together and call the total evapotranspiration. Percolation, by contrast, is water moving down through soil and rock.

Answer: D, about 96.5 per cent. The oceans hold about 96.5 per cent of all Earth's water, according to the USGS. Option C, about 71 per cent, is a trap: that is how much of Earth's surface is covered by water, not how much of the water is in the oceans. Option A, about 2.5 per cent, is roughly the share of Earth's water that is fresh.

Answer: B, about 9 days. Water passes through the atmosphere quickly: on average a molecule spends only about nine days there before falling as precipitation. Other stores keep water far longer. A drop can spend over 3,000 years in the ocean.

Answer: B, tiny particles such as dust, salt or smoke. As air rises it expands and cools. Once it cools to saturation, water vapour condenses, but water molecules on their own are too small to join up into droplets. They need a surface to condense on. Tiny particles called cloud condensation nuclei provide it. Lightning, wind and sunlight are not what makes the vapour condense.

Answer: C, hail. Hail forms in thunderstorms. A frozen raindrop or a small ball of soft ice called graupel is kept from falling by strong rising air, called an updraft. The longer it stays in the cloud, the more water droplets freeze onto it and the bigger it gets. Snow and drizzle do not need a thunderstorm, and dew is not precipitation at all: it forms on surfaces.

Answer: B, deposition. Deposition is water vapour changing straight into ice without becoming liquid first. It makes frost and snowflakes. Sublimation is the reverse: ice turning straight into vapour. It is easy to swap these two in an exam, so learn them as a pair.

Model answer: The white cloud is made of tiny droplets of liquid water. Water vapour is an invisible gas; when the hot vapour from the kettle meets the cooler air of the room it condenses into droplets, and those are what you see. A good answer names condensation and says that vapour is invisible.

Model answer: More water soaks in on the sandy field. Soaking into the ground is called infiltration. Sandy soil lets water in quickly, while the hard surface of a car park lets almost none in, so the rain there becomes surface runoff and flows into drains. A full answer names both processes.

Model answer: False. Small raindrops are nearly round, held together by surface tension. As drops of 2 to 3 mm fall, air pushes on their underside and flattens them, so they look like the top of a hamburger bun. Drops larger than about 4.5 mm become parachute-shaped and break up into smaller drops. None of them is a teardrop.