Unit: Weather I. Heat energy, temperature and the Water Cycle

Why does water change phase Why does water change phase? The water cycle (hydrologic cycle) occurs because water absorbs and releases heat energy. The water cycle moves energy around the world. The water cycle: http://earthguide.ucsd.edu/earthguide/diagrams/watercycle/watercy cleq.html

February 16, 2015 From http://www.hpc.ncep.noaa.gov/images/wwd/radnat/natrad.html

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. Heat is calculated and depends on mass, specific heat and temperature. Weather unit

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. It is also the heat released when an object cools. 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

D. Comparing land and water Weather unit

Heat slowly (absorption) and cool slowly (reradiation). Water tends to: Heat slowly (absorption) and cool slowly (reradiation). Water moderates the temperatures around it. Water absorbs a lot of heat because it: is transparent, has a high specific heat, moves and evaporates. Weather unit

Heat quickly and cool quickly. Land tends to: Heat quickly and 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

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

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

B. Phases of water: p. 1 ESRT properties of water Phase describes the motion of the molecules: Gases are independent and move apart Liquids flow, but stay together Solids are locked in place. Since movement takes energy, solids are the ‘coldest’ Weather unit

C. Water phase change diagram Condensation warms the air around it Evaporation cools the air around it. 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. Weather unit Kentchemistry.com

D. Water is Weird: density michitravel.com Density of water: at 3.98 degrees C, water is its most DENSE!!! 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 air rises…. Weather unit

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

Check understanding and vocabulary Energy is removed from the surface during _____________ and is returned to the air during ________________ Water vapor is a _________ Which changes temperature faster, air or land? Give 2 reasons. The most dense air will be ___________ Not only does water move in the water cycle, but so does _______

Energy from the sun travels to earth through ___________ The heat from hot sand warms the air in contact with it through ____________ Once air is warmed, it rises through the process of _________ In a convection cell, hot fluids ________ and cool fluids _______ Ice floats because it is ________________ than cold water. Specific heat refers to a substances ability to ………….. As winter begins, water loses energy _________ than land does.

What has more heat, the North Atlantic Ocean in February, or a pot of boiling water? _______ Why? ____ What does it meant that water is a ‘moderator’ of heat?