14.3 – NOTES Thermal Properties

B.2 Earth’s Energy Balance Average temperature is 15 C/ 59 F   Properties determine how much thermal energy our planet can hold near its surface 30% of radiation never reaches the surface, but is reflected back to space 70% of radiation reaches the surface 2/3 is absorbed, warming the atmosphere, oceans and continents 1/3 powers hydrologic (water) cycle

Greenhouse gases   Any gas that absorbs infrared radiation CO2, H2O, CH4, N2O, halogenated hydrocarbons, CFCs Greenhouse effect Trapping and returning of IR by carbon dioxide, water, and other atmospheric molecules

The balance of water and CO2 keep our temperature above the estimated -18 C (0F)   Venus has greenhouse to the extreme Venus is 96% CO2 in its atmosphere, so it absorbs a lot more IR, which raises the temperature to 450 C

Climate connections   Interaction of solar radiation and atmosphere also create weather Warm air expands, decreasing density and causing warm air to rise Weather is causes by movement of warm and cold air mass Weather is what is happening at a specific time and location Climate- average weather conditions in an area

Answer the following questions: B.3 Solar Radiation - Why is human exposure to UV radiation potentially more harmful than exposure to IR radiation? 1. UV has a shorter wavelength and more energy than IR. 2. UV has enough energy to break chemical bonds and harm living things. - Describe two essential roles played by visible solar radiation. 1. Visible light activates photoreceptors in eyes allowing us to see 2. Provides energy for photosynthesis - Explain why dry, arid regions in the US such as New Mexico or Arizona experience wider air-temperature fluctuations from night to day than do states with more humid conditions, such as Florida. 1. Water molecules in air trap and reradiate IR even at night, keeping air temperatures about the same. Humid climates have more H2O in the air.

B.4 Thermal Properties at Earth’s Surface Reflectivity The proportion of radiation that is reflected does not raise the object’s temperatures   Light colors stay cooler Snow reflects 95% of light Lawns reflect 15-30%, asphalt none

Specific heat capacity See page 249 Quantity of thermal energy needed to raise 1 g by 1C   Also storage capacity for heat Higher specific heat capacity = store more heat

Metals have low specific heats   Water is unique Very high specific heat (4.18 j/g°C) Can absorb a lot of heat without changing the temperature

Every material has a characteristics reflectivity and heat capacity, which together   Determine how much and how fast the material warms