Investigation 9B  Key Question: How is convection responsible for the movement of air through the atmosphere?? Convection in Earth’s Atmosphere

9.2 Heat transfer  Thermal energy flows from higher temperature to lower temperature. This process is called heat transfer.  There are three ways heat flows:  heat conduction,  convection, and  thermal radiation.

9.2 Heat transfer  Heat conduction is the transfer of heat by the direct contact of particles of matter.  Conduction occurs between two materials at different temperatures when they are touching each other. Where is the heat energy conducted to and from in this system?

9.2 Thermal Equilibrium  When both materials are at the same temperature, they are in thermal equilibrium.  No heat flows when objects are in thermal equilibrium.

9.2 Thermal conductors and insulators  Materials that conduct heat easily are called thermal conductors and those that conduct heat poorly are called thermal insulators. Is a down coat a conductor or an insulator?

9.2 Convection  Convection is the transfer of heat through the motion of matter such as air and water.  The hot water at the bottom of the pot rises to the top and replaces the cold water.

9.2 Convection  Convection is mainly what distributes heat throughout a room.

9.2 Thermal radiation  Heat from the Sun is transferred to Earth by thermal radiation.  All the energy the Earth receives from the Sun comes from thermal radiation.  The higher the temperature of an object, the more thermal radiation it emits.

9.2 Thermal radiation  Thermal radiation is also absorbed by objects.  The amount of thermal radiation absorbed depends on the surface of a material.  Dark surfaces absorb most of the thermal radiation they receive.  Silver or mirrored surfaces reflect thermal radiation.

9.2 Heat transfer, winds, and currents  A thermal is a convection current in the atmosphere.  When a surface, like a road absorbs solar radiation, it emits energy as heat.  The warmed air molecules gain kinetic energy and rise.  Colder air is forced aside and sinks.

9.2 Thermal radiation  There are giant convection currents in Earth’s atmosphere.  The global wind patterns and Earth’s rotation also cause surface ocean currents to move in large circular patterns.

Needed: Efficient Buildings  “Green” building design is the term used to describe architecture that is energy- efficient and environmentally friendly.