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What is Temperature?

What is Temperature?. A property of matter Matter : atoms and molecules Molecules : two or more atoms bound together Examples : H 2 O (water), N 2 (nitrogen), O 2 (oxygen), CO 2 (carbon dioxide) Atoms and molecules are in constant, random motion vibrating rotating

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What is Temperature?

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  1. What is Temperature? A property of matter Matter: atoms and molecules Molecules: two or more atoms bound together Examples: H2O (water), N2 (nitrogen), O2(oxygen), CO2 (carbon dioxide) Atoms and molecules are in constant, random motion vibrating rotating (in gases and liquids) moving from place A form of energy is associated with these random motions kinetic energy (energy of motion) Temperature: a measure of the average kinetic energy of random molecular motions in a substance

  2. What is Heat? Heat is a form of energy Also tied to matter Heat: the total energy of random molecular motions in a piece of matter For a given temperature, the more molecules there are in a piece of matter, the more heat that object has Example: a cup of water taken from the ocean has the same temperature as the water from which it was just taken, but the ocean has far more heat in it than the cup of water does because the ocean has far more molecules, and each molecule contributes a bit to the total heat content of the ocean For a given piece of matter, the higher its temperature, the more heat it has Heat is the form of energy that we can feel in our skin

  3. What Other Forms of EnergyAre There besides Heat? Electromagnetic radiation Emitted and absorbed by electrically charged atoms and molecules Exhibits wave-like behavior as it travels through space Characterized by wavelength Determines how radiation interacts with matter: absorbed, reflected, transmitted, etc. Groups of wavelengths get names: Ultraviolet (UV) visible near-infrared Longwave infrared (LWIR) Etc. Longer wavelengths

  4. What Other Forms of EnergyAre There? A number of others (some will be introduced later)

  5. Principle of Conservation of Energy • Energy cannot be created or destroyed • However, energy canbetransformed from one form to another • Example: (of radiative energy by an object, which gains heat this way) absorption radiative energy sensible heat (of radiative energy by an object, which loses heat this way emission

  6. Principle of Conservation of Energy • Can restate the principle in terms of theheat budget for an object: The ratesat whichthe object loses heatby various mechanisms,added together The ratesat whichthe object gains heat by various mechanisms,added together The rateat whichthe heat content of an object changeswith time = − Note: The faster the object’s heat content changes, the faster its temperature changes

  7. The Heat Budgetfor the Earth’s Surface • For the earth’s surface (water or rock/sand/soil), one way to gain heat is to absorb solar radiation • One way for it to lose heat is to emit radiative energy The ratesat whichthe surfaceloses heatby emitting radiation(plus other mechanisms, added together) The rateat whichthe surface gains heatby solar absorption(plus other mechanisms,added together) The rateat whichthe heat contentof a layer of theearth’s surfacechanges with time = − Note: The faster the heat content of the earth’s surface changes, the faster its temperature changes

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