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II. Heat Energy

II. Heat Energy. A. Temperature is a measure of how fast the molecules hitting the thermometer are. Units are Fahrenheit , Celsius and Kelvin. It is a direct measurement. B. Heat is a measure of the energy of an entire SYSTEM. Units are calories and joules.

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II. Heat Energy

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  1. II. Heat Energy • A. Temperature is a measure of how fastthe molecules hitting the thermometer are. Units are Fahrenheit, Celsius and Kelvin. It is a direct measurement. • B. Heatis a measure of the energyof an entire SYSTEM. Units are calories and joules. • Heat is calculated and depends on mass,specific heat and temperature. Weather unit

  2. C. Heat Capacity Page 1 ESRT: specific heats of common materials • 1. Specific heat is the energy (joules) that you must add to increase the temperature of 1 gram of a substance 1 degree Celsius. • 2. Water has a high specific heat. It takes more than 5 times as much energy to change the temperature of a gram of water as to change the temperature of a gram of granite. Weather unit

  3. D. Comparing land and water Water tends to: • Heat slowly (absorption) and cool slowly (reradiation). • Water moderatesthe temperatures around it. • Water absorbsa lot of heat because it: • is transparent, • has a high specific heat, • moves and • evaporates. Land tends to: • Heat quicklyand cool quickly. • Dry areas have huge changes in temperatures. • Land is opaque; only the top layers are directly heated. • It has a low specific heat. Weather unit

  4. E. Heat Transfer Energy is exchanged when a sourceof energy transfersthat energy to a substance. • Conduction: molecule to molecule through vibration(solids and surfaces) • Convection: in fluids, due to densitydifferences • Radiation: electromagnetic energy travels in waves, through space or materials. Weather unit http://www.spectrose.com/modes-of-heat-transfer-conduction-convection-radiation.html

  5. III. Energy and Phase Changes A. To change iceto water at 0 degrees C, 334joules/gram must be added. • To change liquid to ice, 334joules/gram must be removed. How do you remove heat? it must be ‘lost’ or ‘given’ to the environment. uwsp.edu Weather unit

  6. B. Phases of water: p. 1 ESRT properties of water • Phase describes the motionof the molecules: • Gases are independentand move apart • Liquids flow, but stay together • Solids are lockedin place. • Since movement takes energy, solids are the ‘coldest’ Weather unit

  7. C. Water phase change diagram • Phase change diagram of water can be viewed ‘forward’ (adding heat) or ‘backward’ (removing heat). • Flat lines indicate phase changes. • Sloped lines indicate temperature change. • Condensation warmsthe air around it • Evaporation cools the air around it. Kentchemistry.com Weather unit

  8. D. Water is Weird: density michitravel.com • Density of water: at 3.98 degrees C, water is its mostDENSE!!! the density is 1.0 g/ml • At 0 degrees C, the density of water is less and ice floats!!!!! • Water vapor: the hotter it is, the lighter it is. so, hot airrises…. Weather unit

  9. E. Hot air: expands(takes up more room) and is lighter (rises) and water evaporates (vapor is light) • Cold air: condenses(molecules close together) and water vapor changes phase into water drops. http://science-mattersblog.blogspot.com/2010/08/air-pressure-balloon-in-flask.html Weather unit

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