Coach Book Lesson 13: Heat Transfer

Coach Book Lesson 13

Thermal Energy and Temperature

Temperature is a measure of the average kinetic energy of the particles in a substance

Temperature

Thermal Energy is the kinetic energy of the individual particles-the atoms or molecules-moving within a sample of matter.

Thermal Energy

Heat is the flow of thermal energy. Heat always flows from an area with a higher temperature to an area with a lower temperature. Heat will continue to flow in this way until all materials are at the same temperature.

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Heat

Heat Continued...

Heat can be transferred through all states of matter. If you have ever touched a hot stove, you know that heat can move through solids. You can feel the transfer of heat from a liquid when you take a hot shower. You can feel the transfer of heat from a gas when there is a warm breeze on a summer day.
Heat can also be transferred through a vacuum. A vacuum is an area that contains no matter, not even air.

Multiple Choice

In which direction does heat move?

• 
  from warmer areas to cooler areas

• 
  between areas of equal temperature

• 
  from cooler areas to warmer areas

Multiple Choice

Describe the heat transfer between your hands and a hot mug. In which direction does heat flow?

• The flow of energy is from your cool hands to the warm mug.

• The flow of energy is from the warm mug to your cool hands

• There is no flow of energy between your hands and the warm mug.

Multiple Choice

Heat cannot be transferred through solids.

• True

• False

Conduction

• Conduction is the transfer of heat by direct contact of particles. When you heat a pan on the stove to cook food, the pan is heated by conduction. The thermal energy moves from the stove burner to the pan. Additionally, the food in the pan is also heated by conduction because thermal energy flows from the pan to the food.

• Conduction occurs more readily in solids and liquids, where the particles are closer together than in gases, where particles are further apart.

Convection is the transfer of heat by the movement of currents that form in the fluids. Heat is transferred in fluids (liquids and gasses) by convection.

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Convection

​In the figure above, as the water at the bottom of the pot is heated, its particles are spread apart. As a result, the water at the bottom of the pot becomes less dense than the water at the top of the pot. The cooler, denser water at the top of the pot sinks down, causing the warmer, less dense water to rise. As the cooler water becomes heated, the cycle repeats, with cooler water replacing warmer water below. The rising and falling motion produces convection currents. These currents transfer heat by moving highly energized particles from one area to another.

Multiple Choice

How is convection different from conduction?

• Convection can transfer heat through a vacuum, but conduction cannot.

• 
  Conduction can transfer heat through a vacuum, but convection cannot.

• 
  Convection takes place only in fluids (liquids and gases), but conduction transfers heat in solids as well.

• 
  Convection takes place only in solids, but conduction transfers heat in fluids (liquids and gases) as well.

Multiple Choice

Transfers easily through solids and liquids

• Conduction

• Convection

• Radiation

Radiation

Radiation is the transfer of heat by the movement of radiant energy, such as light and other electromagnetic waves. Radiation DOES NOT require matter to transfer heat. Therefore, radiation can transfer heat through a vacuum.
Examples:
-The heat the Earth receives from the sun is due to radiation.
-Microwave ovens use radiation.

Multiple Choice

Transfers through a vacuum (empty space)

• Conduction

• Convection

• Radiation

Recap

• Heat flows from an area of high temperature to an area of lower temperature. This will continue until all materials are at the same temperature.

• Conduction is the transfer of heat by DIRECT CONTACT of particles.

• Convection is the transfer of heat by the movement of vurrents that form in the fluids.

• Radiation is the transfer of heat by movement of RADIANT energy, such as light and other electromagnetic waves.

Multiple Choice

Transfers most easily through liquids and gases

• Conduction

• Convection

• Radiation

Multiple Choice

The heat you feel from a fireplace moves as a current throughout the room

• Conduction

• Convection

• Radiation

Multiple Choice

Frying a pancake

• Conduction

• Convection

• Radiation

Multiple Choice

Sunrays reaching earth

• Conduction

• Convection

• Radiation

Multiple Choice

IF the image below represents a thermometer hanging inside a flask in which ALL of the air has been removed (a vacuum), which heat transfer method is the ONLY one that can reach the thermometer? 

• Conduction

• Convection

• Radiation

Multiple Choice

A metal spoon is placed in a pot of boiling water. Why does the spoon become hot over time?

• 
  Currents of hot matter travel up the spoon from the water.

• 
  Particles in the water collide with particles in the spoon, which then strike other particles in the spoon, transferring thermal energy.

• Light shining on the spoon causes it to become as hot as the water.

• Microwaves emitted by the hot water are absorbed by the spoon and transformed into thermal energy.