Conduction, Convection, Radiation

Unit 9/Day 3

How does heat energy move?

• Heat always moves from a warmer place to a cooler place.

(Hot Cold)

• Heat transfers in three ways:

– Conduction

– Convection

– Radiation

What is Convection?

• Convection is the transfer of heat by the actual movement of the warmed matter.

• Heat leaves the coffee cup as the currents of steam and air rise. Convection is the transfer of heat energy in a gas or liquid by movement of currents. (It can also happen is some solids, like sand.)

• Consider this:Consider this: convection is responsible for making macaroni rise and fall in a pot of heated water. The warmer portions of the water are less dense and therefore, they rise. Meanwhile, the cooler portions of the water fall because they are denser.

So… then what is Conduction?• Conduction is the transfer of energy through matter from

particle to particle. Also can be referred to as the transfer and distribution of heat energy.

• For example, a spoon in a cup of hot soup becomes warmer because the heat from the soup is conducted along the spoon.

• Conduction is most effective in solids-but it can happen in fluids.

• Fun fact: Have you ever noticed that metals tend to feel cold? Believe it or not, they are not colder! They only feel colder because they conduct heat away from your hand. You perceive the heat that is leaving your hand as cold.

Why does metal feel colder than wood if they are in the same

room? Metal is a conductor and wood is an insulator.

• Metal conducts the heat away from your hands. Wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal.

…and what Radiation?

• Radiation: Electromagnetic waves that directly transport ENERGY through space. Sunlight is a form of radiation that is radiated through space to our planet.

Pop Quiz Question!

• If a cup of coffee and a red popsicle were left on the table in this room what would happen to them?

• Why?

Do colors matter?• Yes!

• Heat excites a black (dark) surface more than a white (light) surface. Black is a good absorber and a good radiator.

• Think of black as a large doorway that allows heat to pass through easily. In contrast, white is a poor absorber and a poor radiator of energy. White is like a small doorway and will not allow heat to pass easily.

Draw 2 examples of conduction.Draw 2 examples of convection.Draw 2 examples of radiation.

Once complete…compare with a partner.

1. Which of the following is not a method of heat transfer?

A. Radiation

B. Insulation

C. Conduction

D. Convection

In which of these are the particles closest together?

A. Solid

B. Liquid

C. Fluid

D. Gas

How does heat reach the Earth from the Sun?

A. Conduction B. Convection

C. InsulationD. Radiation