Conduction Convection Radiation Heat Energy Conduction Convection Radiation
Thermal Energy Thermal energy is the energy of the motion of particles. Remember that particles are small bits that are arranged to form the states of matter.
Heat Heat is the transfer of thermal energy from one piece of matter to another. Heat occurs when thermal energy moves from one object to another.
It takes at least two pieces of matter for heat to be involved. Only one piece of matter is needed for thermal energy.
Heat energy is transferred in three different ways. Conduction Convection Radiation
Conduction Conduction is the transfer of thermal energy by particles bumping into each other Conduction only occurs when particles are in contact with one another Particles bump into one another – when you bump into something you touch it The pot is touching the heating element on the stove which is heating the pot.
Convection Convection is the transfer of thermal energy by particles of a liquid or gas moving from one place to another Convection only occurs in liquids and gases Remember that the particles in a liquid and in a gas are moving.
As the water in the bottom of the pot becomes hot it begins to rise; the water on top which is cooler begins to be pushed down by the warmer water coming up This continues until the whole pot of water is hot
Which of the following could be heated by convection? Remember that convection only occurs in liquids and gases Pictures: fresh water, steel bar, air, glass, ocean water Answers: fresh water, air, ocean water
Radiation Radiation is the transfer of heat by waves that can go through empty space Waves of light coming from the sun
Insulators and Conductors An insulator is a material that doesn’t conduct thermal energy well A conductor is a material that allows thermal energy to pass through easily Insulator helps to keep from going through; Conductor helps it go through (like a conductor on a train...leads the train right through) Foam cup keeps the hot cocoa in our cups, not on our hands; insulated gloves keeps our thermal energy from our hands in our hands and not in the air A metal spoon is a conductor (explain how spoon will burn you if put in pan on stove)
Melting an ice cube Trying to melt the ice cube by warming it in your hands would be an example of conduction.
Trying to melt the ice cube by blowing on it would be an example of convection.
Trying to melt the ice cube by setting it on a warm windowsill would be an example of radiation.
Identify the following pictures as examples of conduction, convection, or radiation.
Conduction – butter melting on corn; ironing clothes; pot heating on stove; walking barefoot on warm sand Convection – water boiling; steam from an iron; heater warming the air; cake baking in an oven Radiation – getting a suntan; sunlight; turtle warming on a log; heated air filling a hot air balloon