Hydrological cycle

Correct answer: A, evaporation. At the ocean surface, solar energy warms liquid water. Some water molecules gain enough energy to leave the surface and enter the atmosphere as invisible water vapour. The change from liquid water to vapour is called evaporation. A is correct because the question describes water vapour forming from a liquid ocean surface. B, condensation, is the reverse change: water vapour cools and becomes liquid droplets, often forming clouds. C, precipitation, is water falling from clouds to Earth as rain, snow, or another form; it occurs after cloud development, not when vapour first forms at the ocean surface. D, runoff, is water flowing over land toward streams, lakes, or oceans, so it describes surface movement after water reaches land. The ocean is an important source of atmospheric moisture because it has a very large surface and water store. Memory cue: liquid to vapour is evaporation; vapour to liquid is condensation; cloud water falling is precipitation; water moving across land is runoff.

Condensation is the process in which water vapour cools and changes into very small liquid water droplets. It is an important step in the hydrological cycle. When moist air rises and becomes cooler, the vapour may condense around tiny particles in the atmosphere, helping clouds form. The same general change can also produce dew when vapour condenses on a cold surface. Thus, condensation changes gas into liquid water.

Option A is correct because it names the cooling of water vapour into droplets. Evaporation is the reverse process: liquid water changes into vapour, usually after gaining heat. Runoff is water flowing over land, while infiltration is water entering the soil. These processes belong to the water cycle but describe different movements or changes. Since the question specifically mentions vapour becoming tiny droplets, the correct term is condensation.

Clouds form mainly when moist air cools enough for water vapour to change into tiny liquid droplets or ice crystals. This change from gas to liquid or solid is called condensation. The particles remain suspended in the atmosphere and appear together as a cloud. Cooling may happen when air rises, expands, or meets other air masses, but the essential cloud-forming process is condensation, not weathering, seismic movement, or tides.

The correct answer is option A, condensation. Weathering breaks down rocks, a seismic wave is a movement caused by an earthquake, and a tide is the regular rise and fall of ocean water. None of these processes directly changes atmospheric water vapour into cloud particles. Evaporation supplies the vapour earlier in the water cycle, but the immediate process that produces clouds is condensation. Therefore, clouds can be understood as groups of condensed water droplets or ice crystals suspended in air.

Correct answer: A, precipitation. In the water cycle, water moves between the atmosphere, land, and water bodies. When water falls from clouds or the atmosphere to Earth’s surface, the process is called precipitation. Rain is liquid precipitation, snow is frozen precipitation, and hail consists of ice particles. A is correct because it includes all three forms. B, evaporation, is the opposite movement: liquid water changes into vapour and rises. C, infiltration, means water entering the soil, usually after reaching the ground. D, salinity, means the amount of dissolved salts in water; it is not a falling-water process. Memory cue: precipitation means water “precipitates” or falls down from the sky.

Correct answer: A, surface runoff. After rain, snowmelt, or another form of precipitation reaches the ground, some water flows across the land surface toward lower areas. This moving water is called surface runoff. It may collect in small channels, streams, and rivers and can ultimately reach lakes or oceans. A is correct because the question describes water flowing over, not into, the land. B, condensation, is the change of water vapour into liquid droplets or ice. C, transpiration, is the release of water vapour by plants, mainly through their leaves. D, salinization, is the accumulation of salts in soil or water. Memory cue: runoff “runs off” the surface.

Correct answer: A, infiltration. Infiltration is the process by which water at the land surface enters the soil through its pores and small openings. Some infiltrated water is held in the soil for plants, while some moves downward through the ground and may recharge groundwater. A is correct because the question specifically describes entry into soil. B, evaporation, changes liquid water into water vapour at the surface. C, condensation, changes vapour into liquid droplets or ice in the atmosphere or on a cool surface. D, precipitation is water falling from the atmosphere; it happens before the water enters the soil. Memory cue: infiltration means water filters in.

Correct answer: A, transpiration. Plants absorb water from the soil through their roots. Water travels through the plant and a large part leaves as water vapour through tiny openings, mainly on the leaves, called stomata. This release is transpiration and it connects plant life with the water cycle. A is correct because it names water-vapour loss from plants. B, precipitation, is water falling from the atmosphere as rain, snow, or hail. C, runoff, is water flowing over the land surface. D, tide, is the regular rise and fall of sea level caused mainly by the gravitational effects of the Moon and Sun. Memory cue: transpiration is like plants “breathing out” water vapour.

Correct answer: A, water vapour. Heat from the Sun causes water from oceans, rivers, lakes, soil, and plants to enter the atmosphere mainly as invisible water vapour. When air rises and cools, some vapour condenses into tiny droplets or ice crystals, forming clouds. Thus vapour is the normal atmospheric form of water before cloud droplets or ice form. A is correct. B, solid rock, is not water and belongs to Earth’s crust. C, salt crystals are dissolved or deposited salts, not the main atmospheric form of water. D, lava is molten rock, not part of the water cycle. Memory cue: water enters the air as vapour; clouds form later by condensation.

Correct answer: A, the largest water reservoir. Oceans store the greatest share of Earth’s total water, so they are the major reservoir in the hydrological cycle. Solar heating causes ocean water to evaporate, and the vapour later returns through precipitation, runoff, and groundwater flow. A is correct because oceans contain far more water than the atmosphere, rivers, lakes, or glaciers considered individually. B is the opposite of the accepted fact. C is wrong because ocean water is saline, not only fresh. D is wrong because groundwater is stored below the land surface, whereas oceans are surface water bodies. Memory cue: oceans are the main store; evaporation is their major link to the atmosphere.

Correct answer: A, seas and oceans. Rain and melting snow provide water to the land. Some of this water flows downhill as surface runoff and gathers in streams and rivers. Because rivers generally follow the slope of the land, they carry water toward lakes, seas, and ultimately the oceans, although some water may infiltrate, evaporate, or be used before reaching them. A is correct as the usual final destination of river flow. B is not a general destination, and C is unrelated to ordinary drainage. D describes the atmosphere, not the normal path of river water. Memory cue: rivers are the land-to-ocean link.

Correct answer: A, solid ice. A glacier is a large, persistent mass of ice formed when snow accumulates and is compressed over a long period. Therefore, water in a glacier is stored mainly in the solid state. Glaciers are important freshwater stores, and melting can supply streams and rivers. A is correct because ice is the solid form of water. B, water vapour, is an invisible gas present in the atmosphere. C, hot steam, is also gaseous water and is not the normal condition of a glacier. D, salt solution, describes salty liquid water, whereas glacier ice is not a salt solution. Memory cue: glacier means stored snow and ice, not atmospheric vapour.

Correct answer: A, infiltration of water into soil. Rain or melting snow can enter the ground through soil pores. After infiltration, part of the water moves downward through permeable soil and rock; this downward movement is often called percolation. When water reaches and fills underground saturated layers, it becomes groundwater and may later feed wells, springs, streams, or rivers. A is correct because infiltration begins this recharge pathway. B, tides, are regular movements of sea level and do not directly form groundwater. C concerns volcanic rock, not water storage. D has no hydrological role. Memory cue: groundwater begins when surface water goes into the ground.

Correct answer: A, higher temperature. Evaporation is the change of liquid water into water vapour at a surface. When temperature is higher, water molecules gain more energy, so more of them can escape from the surface into the air. Strong sunlight commonly provides this energy, although wind and dry air can also affect the rate. A is correct because increased temperature generally increases evaporation. B, less sunlight, usually supplies less energy and therefore does not increase evaporation. C, still cold air normally reduces evaporation. D, more freezing changes liquid water to ice, not vapour. Memory cue: heat helps water escape into the air.

Correct answer: A, toward land areas. Solar heat changes some ocean water into water vapour. Because vapour is present in the moving atmosphere, winds can carry it away from the ocean and over nearby or distant land. When the moist air rises and cools, the vapour may condense into clouds and later produce precipitation, such as rain. Thus, movement of moisture from ocean to land is an important part of the hydrological cycle. A is correct because winds transport moisture to land. B is wrong because vapour moves through the atmosphere, not only into the ocean floor. C is wrong because ordinary atmospheric transport does not take vapour to Earth’s core. D is wrong because water is not permanently trapped inside rocks in this process. Memory cue: ocean water evaporates, winds transport the vapour, and rainfall may return it to land.

Correct answer: A, through rivers and runoff. After rain falls on land, some water flows over the surface into small channels, streams, and rivers. This movement is called surface runoff. Rivers generally carry the collected water downhill, eventually bringing much of it to lakes, estuaries, and oceans. Some rainwater also infiltrates the ground, moves as groundwater, and may later reach the sea, but the option that gives the main visible route is rivers and runoff. A is correct because flowing water connects land with the oceans. B is wrong because lightning is an electrical discharge and does not transport the collected water back to the sea. C is wrong because dust cannot carry the required volume of water. D is wrong because the Moon influences tides but does not carry rainwater through the drainage system. Memory cue: rainfall on land flows downhill; rivers complete the land-to-ocean route.

Correct answer: A, solar energy. The Sun supplies the heat that causes evaporation from oceans, lakes, rivers, soil, and vegetation. The water vapour rises, cools, condenses into clouds, and returns as precipitation. Solar heating also creates differences in temperature and pressure that help drive atmospheric circulation and wind, which transport moisture. Gravity is also important because it pulls precipitation downward and helps water flow downhill, but the main external energy source that starts and sustains the cycle is the Sun. A is correct for this reason. B is wrong because nuclear energy is not the ordinary driving source of atmospheric evaporation. C is wrong because earthquakes do not power the global water cycle. D is wrong because magnetism does not provide the heat needed for evaporation. Memory cue: the Sun lifts water as vapour; gravity brings it back down.

Correct answer: A, precipitation and runoff. Gravity attracts matter toward Earth. It helps water droplets and ice particles fall from clouds as precipitation. After reaching the ground, gravity makes water move from higher to lower places as surface runoff, streams, and rivers. It can also help water move downward into the soil. A is correct because both falling water and downhill flow show gravity directly. B is wrong because condensation is the change of vapour into liquid or ice and does not mean a colour change caused by gravity. C is wrong because salt formation is related to dissolved minerals and evaporation, not the clearest gravitational action. D is wrong because sunlight is energy from the Sun, not something formed by gravity in the water cycle. Memory cue: gravity makes water fall and flow downhill.

Condensation is the change in which water vapour becomes tiny liquid water droplets. Air can hold less water vapour when its temperature falls. If moist air cools to a suitable point, the vapour changes into droplets on particles in the atmosphere, and these droplets may help form clouds or fog. Thus, cooling is the important condition that encourages condensation in the hydrological cycle.

The correct answer is A, “cooling of air.” Drying of the ocean would reduce an important water source rather than directly provide the needed condition. Melting rock is unrelated to the atmospheric change of vapour into droplets, and a complete absence of air would not describe the usual process of cloud formation. In the water cycle, evaporation adds vapour to the atmosphere and cooling later supports condensation. Remembering this sequence makes the answer clear without confusing condensation with evaporation.

Correct answer: A, evaporation. Solar heating gives water molecules at the ocean surface enough energy to change from liquid water into water vapour. The vapour then enters the atmosphere and may be transported by winds. Later, cooling can cause condensation and cloud formation, but condensation is not the process that takes water from the ocean into the air. A is correct because it describes the ocean-to-atmosphere movement. B is wrong because runoff normally carries water across land toward lower areas and often toward the ocean. C is wrong because infiltration means water entering soil or rock, so it is a downward land process. D is wrong because contraction is not the standard hydrological-cycle term for this transfer. Memory cue: evaporation goes up from a wet surface; precipitation comes down from the atmosphere.

Correct answer: A, precipitation. Water vapour in the atmosphere may condense into cloud droplets or ice particles. When these particles become large or heavy enough, they fall toward Earth’s surface as rain, snow, sleet, or hail. This downward delivery of water is collectively called precipitation. A is correct because it covers the atmosphere-to-surface movement. B is wrong because evaporation moves liquid water from a surface into the atmosphere, the opposite direction. C is wrong because transpiration is the release of water vapour from plant leaves into the atmosphere. D is wrong because ocean salinity describes the amount of dissolved salt in seawater, not falling water. Memory cue: precipitation comes down; evaporation and transpiration send water up.

Correct answer: A, runoff. Rain or melted snow that does not immediately infiltrate into the soil can flow across the land surface. It gathers in channels, streams, and rivers and is carried toward lower ground, often eventually reaching an ocean. This flowing water is called surface runoff. A is correct because it describes land-to-ocean movement through rivers. B is wrong because condensation changes water vapour into liquid droplets or ice, usually in the atmosphere. C is wrong because evaporation changes liquid water into vapour and moves it upward. D is wrong because snowfall is precipitation in the form of snow; it may later contribute to runoff after melting, but it is not the river flow itself. Memory cue: runoff runs over land, while rivers are its visible pathways to the sea.

Correct answer: A, lakes. A lake is a body of water that can hold freshwater on or near the land surface for a period of time. It is called a temporary store because water can enter through rainfall, streams, or groundwater and later leave through rivers, seepage, or evaporation. Lakes therefore act as reservoirs within the hydrological cycle, although their size and storage time vary. A is correct because lakes are important surface stores of freshwater. B is wrong because lava is molten rock, not a normal freshwater store. C is wrong because sea salt is a dissolved mineral and does not store freshwater. D is wrong because desert dust consists of dry particles and is not a major freshwater reservoir. Memory cue: lakes temporarily hold freshwater between rainfall, runoff, and evaporation.

Correct answer: A, rain. Rain is liquid water that falls from clouds as drops. It forms when water vapour condenses into cloud droplets and the droplets combine or grow enough for gravity to pull them downward. Rain is one common form of precipitation; other forms may include snow, sleet, or hail, depending on atmospheric temperature and conditions. A is correct because the question specifically says the water is liquid and falling from clouds. B is wrong because fog is a cloud near the ground, not falling liquid water. C is wrong because dew forms as water droplets on cool surfaces near the ground. D is wrong because mist is a very fine suspension of droplets near the surface, not cloud water falling as rain. Memory cue: rain falls from clouds; fog and mist stay near the ground, while dew forms on surfaces.

Correct answer: A, snowfall. Snowfall is precipitation that reaches the ground as snow, made of ice crystals or groups of ice crystals. It forms in cold clouds when water freezes or deposits as ice, and the crystals remain solid while falling through sufficiently cold air. A is correct because it names solid precipitation in the form of snow or ice crystals. B is wrong because evaporation is the change of liquid water into vapour and moves water upward. C is wrong because infiltration is the movement of water into soil or rock after it reaches the ground. D is wrong because runoff is water flowing over land toward lower areas. A useful caution is that all precipitation is not snowfall: rain is liquid, while snowfall is solid. Memory cue: snow falls as ice crystals; rain falls as liquid drops.

Correct answer: A, salts remain behind during evaporation. The Sun heats ocean water, and some of the water changes from liquid into water vapour. This vapour rises, while dissolved salts and most other impurities do not evaporate with it. Higher in the atmosphere, the vapour cools and condenses into tiny droplets or ice particles, forming clouds. When these particles become large enough, precipitation falls as mostly fresh rainwater. Option A is correct because evaporation separates water from dissolved salt. Option B is wrong because sea salt does not normally rise with the water vapour into clouds. Option C is wrong because the whole ocean does not become fresh; only some water evaporates. Option D is wrong because waves are movements of liquid water, not clouds. Memory cue: evaporation carries water upward but leaves salt behind—like natural distillation.