Heat Transfer: Conduction,Convection, and Radiation

Why do metals make the best conductors?

Thermal energy transfers more rapidly in metals than in other materials. Because: 1. electrons are not bound to individual atoms 2. electrons are "free" moving 3. there are more collisions between the electrons and other particles in the metal

Which is the ONLY METHOD of energy transfer than can occur through a VACUUM? (and I don't mean "vacuum cleaner")

Radiation

What is not sent along with the energy?

matter

Examples of POOR thermal insulators

Remember..."good conductors are poor insulators AND poor conductors are good insulators" METALS are POOR INSULATORS

conduction

the transfer of thermal energy by collisions between particles that make up matter. The direct transfer of heat from one substance to another substance that it is touching

convection

the transfer of thermal energy by the circulation or movement of a liquid or gas.

Radiation

The transfer of energy by electromagnetic waves. This type of energy transfer does not require the presence of molecules

Briefly describe how conduction transfers energy from one point to another.

transfers thermal energy through direct contact. A burner on the stove transfers heat to a pan on the burner as particles with more kinetic energy transfer kinetic energy to particles with less kinetic energy.

Why are gases the best at transmitting radiation?

Because gas particles are further apart, the radiation energy travels through the space between the particles. Radiation travels MORE RAPIDLY and EFFICIENTLY through GASES.

What is the direction of energy flow?

Conduction, convection and radiation spread thermal energy from warmer areas to cooler areas.

Three methods of heat transfer?

Conduction, convection, and radiation are three ways to transfer energy.

4 Examples of GOOD thermal insulators

1. Wood 2. Styrofoam 3. Fiberglass 4. Air

Describe how a THERMOS works as an INSULATOR

A thermos is constructed to reduce energy transfers between the bottle's contents and its surroundings. There is a small amount of air between the two surfaces of the bottle. This minimizes transfers of thermal energy by conduction and convection.

Which method of energy transfer can ONLY OCCUR in FLUIDS?

Convection can only occur in liquids or gases

Why are gases worse at conduction than solids or liquids?

In gases, particles are farther apart. Therefore, collision among particles occur less frequently in gases.

Thermal Insulators

Materials that are poor conductors of heat. Material through which thermal energy moves SLOWLY

Example of CONDUCTION

Picking up a hot cup of coffee A mother bird transferring body heat by sitting on her eggs. A spoon being heated while sitting in a hot bowl of soup

Describe how a JACKET works as an INSULATOR

The fibers in fleece trap the air and hold it next to you. The air slows the transfer of your body's thermal energy into its surroundings.

Describe how convection currents form. THINK ABOUT A LAVA LAMP

Warmer, less dense fluids (gas or liquid) rise and more dense fluids (gas or liquid) sink. As the less dense (or warmer) fluids rise they COOL. Convection currents TRANSFER THERMAL ENERGY from warmer to cooler parts of the fluid. In a convection current BOTH CONDUCTION and CONVECTION transfer thermal energy.

Can radiation travel through solids, liquids and gases? How does radiation travel through solids, liquids, gases?

Yes Radiation waves strike a material. Some of the energy can be 1. absorbed 2. reflected 3. or transmitted