Energy Transfer in the Atmosphere

What you will learn Describe what happens to the energy Earth receives from the sun. Compare and contrast radiation, conduction, and convection.

Vocabulary Radiation Conduction Convection Hydrosphere Condensation

Energy from the Sun The Sun provides most of the energy on Earth. When Earth receives energy from the Sun the energy is reflected back into space by: Clouds Atmospheric particles Earth’s surface The rest is absorbed by land and water on Earth’s surface.

Heat Heat is energy that flows from one object with a higher temperature to an object with a lower temperature. Heat is then transferred through the atmosphere in three ways: Radiation Conduction Convection

Radiation RADIATION Earth radiates some of the energy it absorbs from the Sun back toward space. Radiant energy warms the surface. It even warms your face.

CONDUCTION If you walked barefoot on a hot beach, your feet heat up because of conduction. Radiation from the sun heated the beach sand. Conduction is your feet and the direct contact with the sand.

Conduction Returning to the example of a camp fire. What happens if we use an old metal hanger to roast marshmallows? As the marshmallows cooks, the fire heats the end of the hanger. If we leave the hanger in the fire long enough, eventually the end we are holding will become too hot for us to handle. This happens despite the fact that this end was never placed into the flames. Heat was transferred from the flames to the metal, and then from molecule to molecule in the hanger via conduction until it reached your sensitive fingers.

Question? What would happen if you had chosen a stick to roast your marshmallows on, instead of a metal hanger?

Conduction Not all objects are good conductors of heat. Though the stick may have caught fire, it would not have conducted the heat to your hand. This is because wood is a very poor heat conductor.

Convection After the atmosphere is warmed by radiation or conduction, the heat is transferred by a third process called convection. Convection is the flow of heat throughout the atmosphere. How does this happens?

Radiation What happens in space? There are no solids touching the sun for conduction to occur There are no fluids in space for convection to occur Therefore, heat travels by radiation

Conduction, Convection, and Radiation together distribute the Sun’s heat throughout the Earth

Lesson Essential Question: How is energy transferred as heat? Summarizing Strategy: On the following slides, identify whether the statement describes cooking popcorn using conduction, convection, or radiation.

Put oil in the bottom of a pan Put oil in the bottom of a pan. Cover the bottom of the pan with popcorn kernels. Place the pan on the stove and turn on the burner to medium heat. Cover the pan with a lid. Periodically shake the pan so the kernels move around in the oil.

And the answer is… Conduction The heat is transferred by direct contact from the pan, to the oil, to the kernels of popcorn.

Microwave a bag of popcorn.

And the answer is… Radiation The kernels are heated by the radiation in the microwave.

Cooking popcorn in a popcorn popper.

And the answer is… Convection The hot air transfers the heat to the cooler kernels, and when enough hot air heats the kernels they pop.