Heating and cooling of the atmosphere

The correct answer is A. During the night, Earth’s surface loses energy by emitting longwave, or terrestrial infrared, radiation. Water vapour is a greenhouse gas that absorbs part of this outgoing radiation and re-emits energy in several directions. Some of the re-emitted energy travels downward toward the surface, so the surface loses heat more slowly than it would under a very dry sky. Consequently, when other conditions are similar, a humid or moist night can remain relatively warmer than a dry night. Option B is wrong because high humidity may reduce evaporation, but it does not completely stop it. Option C is wrong because water vapour does not create or increase sunlight at night. Option D is wrong because adding water vapour does not increase atmospheric oxygen. This effect is about the rate of radiative cooling, not about producing heat from nowhere. Memory cue: humid skies act like a partial blanket against night-time heat loss.

Earth’s surface emits energy mainly as longwave, or infrared, radiation. Water vapour and carbon dioxide absorb parts of this outgoing radiation and re-emit energy in different directions, including back toward the surface. This greenhouse action influences the balance between incoming solar energy and outgoing terrestrial energy. Thus option A is correct; the other choices misidentify their nature or effect.

Direct answer: Option A is correct. Methane is a trace gas, meaning it occurs in much smaller concentration than nitrogen and oxygen. Nevertheless, its molecules absorb outgoing infrared radiation, so methane is an important greenhouse gas. An increase in atmospheric methane can contribute to warming and changes in Earth’s heat balance. B is wrong because methane is not a principal gas used in respiration by humans or most animals. C is wrong because methane is not chemically inert; it can participate in chemical reactions and can burn. D is wrong because methane is a gas, not merely a solid or liquid condensation nucleus. The word “only” also makes those alternatives too narrow. The key idea is that atmospheric importance depends not only on quantity but also on the radiative properties of a gas. Memory cue: trace amount, strong heat-trapping role.

The governing concept is the greenhouse effect and the interaction of gases with terrestrial longwave radiation. Water vapour absorbs some outgoing infrared radiation and re-emits energy in different directions, including back toward the surface, which can retain heat. Thus option A is correct. It does not make all radiation disappear, convert nitrogen into rock, or remove atmospheric oxygen, so B, C, and D are incorrect.

Option A is correct because water vapour absorbs some of the outgoing longwave infrared radiation released by Earth’s surface at night. The absorbed energy is re-emitted in several directions, including downward, so radiative cooling is reduced and the night may remain relatively warmer. Option B reverses this process. Option C incorrectly focuses on reflected sunlight, which is absent at night, and option D invents a change in nitrogen concentration. Clouds can strengthen a similar night-warming effect, although actual temperature also depends on wind, humidity, and surface conditions.

The correct answer is A. Aerosols are tiny particles or droplets suspended in air. Depending on their size and composition, they can scatter or reflect incoming radiation, changing visibility and affecting how much solar energy reaches the surface. They may also absorb radiation, so their effects are not all the same.

Direct answer: D is correct. The percentage of a gas tells us how much of it is present, but its chemical and physical properties tell us what it does. Nitrogen and oxygen are abundant, yet gases present in smaller amounts can be extremely important. Carbon dioxide and water vapour absorb outgoing heat and influence temperature, clouds and climate. Ozone absorbs much harmful ultraviolet radiation even though it forms only a very small part of the atmosphere. Therefore, quantity alone cannot explain atmospheric behaviour. A is wrong because percentage is meaningful for measuring abundance. B is wrong because gases have different properties. C is wrong because colour does not explain climate. D correctly connects a gas's amount with its function. Memory cue: “Amount tells how much; properties tell what it does.”

Direct answer: C is correct. The diurnal temperature range is the difference between the maximum temperature during the day and the minimum temperature at night. Water vapour is a greenhouse gas: it absorbs part of the long-wave radiation emitted by Earth’s surface. At night this slows surface cooling, so the minimum temperature may remain higher. Water vapour can also help form clouds; clouds may reduce daytime solar heating and nighttime heat loss. Both effects often narrow the day–night difference, although the exact result varies with cloud cover, wind and other conditions. A is impossible because no ordinary atmospheric process makes the range infinite. B ignores water vapour’s radiative role. D is unrelated to temperature range. C gives the correct general effect.

Direct answer: D is correct. Carbon dioxide has both a useful biological role and a climate-related role. Green plants take in CO₂ during photosynthesis and use it, together with water and light energy, to make food; oxygen is released as a product. Without an adequate carbon dioxide supply, photosynthesis and plant growth could not proceed normally. At the same time, CO₂ absorbs some outgoing infrared radiation and is therefore a greenhouse gas. A is wrong because CO₂ can affect temperature through the greenhouse effect. B is wrong because CO₂ is not sea salt. C is wrong because it is a compound of carbon and oxygen, not solid oxygen. The key distinction is amount: necessary CO₂ is not the same as excessive CO₂. Memory cue: CO₂ feeds plants, but too much can disturb climate.

The correct answer is B: latent heat affects cloud systems and weather energy. During evaporation, water takes in energy and stores it as latent heat. When water vapour later condenses into liquid droplets, that stored energy is released into the surrounding air. The local warming can change buoyancy, convection, pressure patterns, and the development of clouds. In suitable conditions, this energy can help strengthen storms, although it does not automatically create severe weather. A is wrong because winds are not permanently stopped. C is wrong because nitrogen is not changed into dust. D is wrong because condensation cannot end solar energy. Memory cue: evaporation stores heat; condensation releases it.

A is correct. Water vapour can condense into cloud droplets or ice crystals as moist air cools. Condensation releases latent heat, which can strengthen rising air and convection. These processes help shape clouds and precipitation and can influence weather systems. Moisture alone does not determine the weather; temperature, winds, and atmospheric stability also matter.

Direct answer: A is correct. Ozone in the stratosphere absorbs a substantial part of incoming ultraviolet radiation from the Sun. The absorbed radiation transfers energy to the ozone and surrounding air, and that energy becomes thermal energy. This radiative heating helps create the stratosphere’s characteristic temperature pattern: through much of the layer, temperature generally increases with altitude because ozone absorption is important there. The exact temperature profile also depends on radiation, circulation, and chemistry, but ultraviolet absorption is the key idea tested here. B is wrong because ozone does not turn all atmospheric gases into liquids. C is wrong because Earth’s shadow is not removed by ozone. D is wrong because ozone does not stop ocean currents. Memory cue: “Ozone absorbs ultraviolet radiation, so the stratosphere is heated from within by absorption.”

Direct answer: A is correct. During the day, dry desert ground can receive strong sunlight and heat rapidly, especially when cloud cover is limited. After sunset, the surface loses energy by emitting infrared radiation. Water vapour is an important greenhouse gas that absorbs and re-emits some outgoing longwave radiation. A dry atmosphere contains less water vapour, so less of this radiation is returned downward and more heat escapes to space. The night therefore cools quickly, while daytime heating remains strong, producing a large day-night temperature range. A is correct, although wind, clouds, soil, and surface properties also affect the actual range. B is wrong because deserts receive sunlight. C is wrong because sand is not a major oxygen-producing organism. D is wrong because polar ice is not a normal feature of hot deserts. Memory cue: “Dry air lets daytime heat build and nighttime heat escape.”

Answer: A. Dust, soot and smoke are particulate pollutants, often called aerosols. They can scatter sunlight, absorb radiation and reduce visibility, producing haze. Because they change how much incoming solar energy reaches the ground and how much energy is absorbed or reflected, they can disturb the local radiation balance. Urban particles may also influence cloud formation and therefore local heating, cooling or rainfall, although the exact effect depends on particle type and weather conditions. A is correct because it combines the direct air-quality effect—pollution and haze—with the climatic effect on radiation. B is wrong because particles cannot remove Earth’s gravity. C is wrong because buildings cannot all become glaciers as a consequence of urban smoke. D is wrong because smoke and dust do not generally turn seawater into freshwater. A useful warning is that aerosols do not always produce the same amount or direction of warming; their effect depends on composition, size, altitude and surrounding conditions.

Answer: A. Temperature affects both evaporation and the amount of water vapour air can contain before reaching saturation. When a surface such as a lake, soil, or ocean becomes warmer, water molecules escape more readily into the air, so evaporation can increase. Warmer air can also hold more water vapour before condensation begins. If that moist air later cools, it may reach saturation and form clouds, fog, or precipitation. B is wrong because heating does not end gravity. C is wrong because heat does not turn nitrogen into the sea. D is wrong because warm air still contains gases, including nitrogen, oxygen, and water vapour. “Can hold more” is a capacity statement, not a guarantee that every warm place is more humid; actual humidity also depends on water supply and circulation.

Answer: A. Carbon dioxide is a greenhouse gas, so its increase can influence temperature, but its effects extend through several connected Earth systems. The carbon cycle changes because more carbon is present in the atmosphere and exchanges occur among air, vegetation, soil and oceans. Oceans absorb part of the additional CO₂; this changes seawater chemistry and can contribute to ocean acidification. Plants use CO₂ in photosynthesis, so increased concentration can affect plant growth, although the response depends on water, nutrients, temperature and species. B is wrong because CO₂ does not immediately reverse all river directions. C is wrong because it cannot stop Earth’s rotation. D is wrong because it does not remove all atmospheric nitrogen. Memory cue: CO₂ links air, oceans, plants and climate—not temperature alone.

B is correct. Aerosols are tiny particles or droplets suspended in air. They can scatter sunlight and some can absorb radiation, changing how much solar energy reaches the surface. The effect depends on the aerosols' properties and atmospheric conditions.

A is correct. At night, Earth's surface loses energy by emitting longwave infrared radiation. Water vapour can absorb some of this outgoing radiation and re-emit energy, including back toward the surface. This can reduce night-time cooling, so humid regions may have warmer nights than dry regions under comparable conditions.

Direct answer: A is correct. The biosphere includes living organisms, and life continuously exchanges gases with the atmosphere. Plants take in carbon dioxide for photosynthesis and release oxygen; animals and many microorganisms use oxygen in respiration and release carbon dioxide. At the same time, carbon dioxide, water vapour, methane, and other greenhouse gases absorb part of the outgoing infrared radiation from Earth and influence atmospheric temperature. Thus biological activity can alter atmospheric composition, while temperature and climate conditions affect ecosystems, habitats, and species. B is too narrow and incorrect because gases do much more than form rocks. C is false because the atmosphere is central to climate. D is false because the biosphere and atmosphere interact continuously. The statement concerns balance: both too little and too much of a gas can have important consequences. Memory cue: life changes the air, and the air helps shape life’s climate.

Correct answer: A. Earth’s surface absorbs solar energy and later releases energy mainly as longwave infrared radiation. Water vapour absorbs some wavelengths of this outgoing radiation and re-emits energy in several directions. Some energy is directed back toward the surface, while some moves upward, so water vapour affects the rate at which the atmosphere and surface lose heat. Water vapour also participates in clouds and transfers latent heat when water evaporates and condenses, but the radiative property stated in A is the direct basis asked in this question. Option B is wrong because water vapour does not colour all gases. Option C is wrong because gravity is not stopped by water vapour. Option D is wrong because atmospheric water vapour does not liquefy nitrogen as its main function. Memory cue: greenhouse gases regulate heat by absorbing and re-emitting outgoing infrared radiation.

Direct answer: A is correct. Stratospheric ozone has two connected roles. First, it absorbs much of the biologically harmful ultraviolet radiation that would otherwise reach Earth’s surface. This protective filtering reduces damage to living organisms. Second, the absorbed ultraviolet energy is converted into thermal energy within the stratosphere. Because ozone absorption adds heat at particular heights, it helps produce the stratosphere’s characteristic temperature pattern, including warming with height through much of that layer. B is wrong because ozone does not turn all gases into liquids. C is unrelated to ozone absorption, and D has no valid connection with ocean acidity. A useful warning is that ozone is beneficial in the stratosphere because it shields life, whereas ozone near the ground is a pollutant; the location matters. Memory cue: stratospheric ozone “absorbs UV and warms the layer.”

The correct answer is A. Water vapour is an important greenhouse gas because it absorbs part of the outgoing infrared radiation released by Earth’s warmed surface. By absorbing and re-emitting this energy, it helps influence the balance between incoming solar energy and outgoing terrestrial heat. Water vapour also changes phase: evaporation uses heat, while condensation releases latent heat. Clouds formed from condensed water can reflect some sunlight and also absorb outgoing infrared radiation, so their net effect depends on conditions. B is wrong because water vapour does not always make temperature zero. C is wrong because its effect is not limited to cooling nitrogen; it influences the whole atmospheric energy balance. D is wrong because water vapour and clouds do not completely block sunlight. Memory cue: “water vapour stores and moves heat.”

Correct answer: C. Earth’s surface emits energy mainly as longwave infrared radiation. Carbon dioxide absorbs some of this outgoing radiation and re-emits energy in different directions, including toward the surface. This greenhouse effect affects how quickly heat escapes to space, so carbon dioxide can influence climate even at a relatively low concentration.

Correct answer: A. The daily temperature range is the difference between the day’s maximum and the night’s minimum temperature. Water vapour absorbs and re-emits some outgoing infrared radiation. This can slow cooling at night, keeping the minimum temperature higher and reducing the day–night range. This is a general effect; clouds, wind, and local conditions also matter.

Correct answer: B. Strong solar heating near the equator warms the air, promoting vigorous convection and upward movement. This makes the troposphere extend higher there, so its upper boundary—the tropopause—is at a greater altitude than in polar regions.