The Water Cycle — Practice · Grade 9 Science

Chapter: Atmosphere & Weather

What this practice covers

By the end of The Water Cycle you should be able to:

10 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: evaporation, condensation, precipitation, transpiration.

Problem 1

Which process changes liquid water into water vapor, mostly from the surface of the ocean?
  1. Evaporation
  2. Condensation
  3. Precipitation
  4. Infiltration
Answer and explanation

Evaporation

The sun's energy heats liquid water until it evaporates into invisible water vapor.

Problem 2

What is it called when plants release water vapor through their leaves?
  1. Transpiration
  2. Respiration
  3. Condensation
  4. Sublimation
Answer and explanation

Transpiration

Transpiration is water vapor released through tiny openings in plant leaves; combined with evaporation, it's called evapotranspiration.

Problem 3

Rising air cools, and water vapor changes into the tiny liquid droplets that form clouds. What is this process called?
  1. Precipitation
  2. Condensation
  3. Runoff
  4. Evaporation
Answer and explanation

Condensation

Condensation happens when rising, cooling air causes water vapor to turn back into liquid droplets, forming clouds.

Problem 4

About what percent of all the water on Earth is salty ocean water?
Answer and explanation

97 %

Around 97% of Earth's water is salty ocean water; only about 3% is freshwater, and most of that is locked up as ice.

Problem 5

The water cycle is powered by two forces. Name both, and explain which part of the cycle each one drives.
Answer and explanation

The sun's energy drives evaporation and transpiration, lifting liquid water into the air as vapor. Gravity pulls condensed water back down as precipitation and pulls runoff downhill into rivers, lakes, and groundwater.

Problem 6

A covered cold glass collects water outside. Explain its likely source. Explain the reasoning in your own words.
Answer and explanation

The droplets can come from the air, rather than leaking through the glass.

Moist air contacts the colder surface and cools.

Some water vapor condenses into liquid on the outside.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 7

Name a water-cycle route from soil to atmosphere through plants. Show the reasoning, not just the conclusion.
Hints

Matter cycling does not mean energy follows the same closed loop.

Answer and explanation

Root uptake followed by transpiration releases water to the atmosphere.

Problem 8

Why can a local lake shrink even though global water is conserved?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Its local outflows can exceed inflows; global conservation does not require constant storage in each reservoir.

Problem 9

Equal rainfall can produce different surface pathwaysEqual rainfall can produce different surface pathwaysVolume in one supplied test (mL)Rain input100Runoff35Infiltration45Surface storage20100 = 35 + 45 + 20; equal rain can partition differently.
Original supplied short-test water partition. The 100 mL input is balanced by runoff, infiltration and temporary surface storage. Actual precipitation-to-runoff behavior also depends on conditions and additional terms; the diagram is not a universal landscape partition.
Interpret the supplied visual model. If runoff becomes 55 mL and surface storage stays 20 mL with the same 100 mL input, what infiltration remains under the stated model?
Answer and explanation

25 mL, because 100−55−20 = 25. The calculation assumes all relevant transfers and stores have been included over the matched interval.

Account for all the stated pathways over the same test interval. The bars are volumes rather than rates; the example neglects evaporation during the short test.

25 mL, because 100−55−20 = 25. The calculation assumes all relevant transfers and stores have been included over the matched interval.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 10

A lake starts at 250 m³. Daily input is 40 m³ and output 28 m³ for five days. Find final storage and explain why the height change cannot be determined from these data alone.
Answer and explanation

Net input is 12 m³/day, so storage gains 60 m³ and reaches 310 m³. Lake area/shape or a volume-level relationship is needed for height change.

Subtract 40−28 = 12 m³/day.

Multiply by five days to obtain 60 m³ and add to 250.

Distinguish volume from height and request geometry.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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