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photochemical a chemical reaction caused by light

precipitation water released from clouds as rain, snow, hail, or sleet

radiate to emit energy in the form of rays, heat, and waves

reservoir a large quantity of something that can be used anytime

sedative a medicinal drug that makes one fall asleep

semiconductor a solid substance that allows electricity to pass through it when its temperature increases

smog a mixture of smoke and fog in the atmosphere

solvent a substance which is capable of dissolving a solid substance

stratosphere a part of Earth’s atmosphere that is 10–50 km above the surface

sublimation the process in which a solid substance changes into gas or vice versa without becoming liquid

topography the physical features of the earth such as hills, mountains, rivers, etc.

transpiration the process in which water from leaves passes into the atmosphere as water vapor

volatile any liquid or substance that can quickly change into gas

wetland an area of land fully or partially submerged in water

The Danger of Greenhouse Gases

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