Heat Transfer Conduction, Convection and Radiation

Question If a cup of coffee and a red popsickle were left on the table in this room what would happen to them? Why? The cup of coffee will cool until it reaches room temperature. The popsickle will melt and then the liquid will warm to room temperature.

To Make Foldable: Conduction Convection Radiation Heat Transfer 1. On the short side of the paper, fold it down an inch. 2. Now fold it in half, hamburger style. 3. Now fold it in 1/3. Outside of Foldable Inside of Foldable Conduction Convection Radiation Examples Definition Heat Transfer

Thermal Energy Transfer Thermal energy transfer is heat moving from a warmer object to a cooler object. This is known as thermal energy transfer.

Heat Transfer Heat always moves from a warmer place to a cooler place. Hot objects in a cooler room will cool to room temperature. Cold objects in a warmer room will heat up to room temperature.

How is Heat Transferred? There are THREE ways heat can move. Conduction Convection Radiation

CONDUCTION Heat is transferred from one particle of matter to another in an object without the movement of the object. Conduction = Heat transfer by CONTACT/TOUCH

Have you ever… Touched a metal spoon sitting in a pan of boiling water only to be surprised by HOW hot it is?? Think back to what you know about metals and nonmetals. What conducts heat better, metal or nonmetal? Why?

Example of Conduction Think of a metal spoon in a pot of water being heated. The fast-moving particles of the fire collide with the slow-moving particles of the cool pot. Because of these collisions, the slower particles move faster and heat is transferred. Then the particles of the pot collide with the particles in the water, which collide with the particles at one end of the spoon. As the particles move faster, the metal spoon gets hotter. This process of conduction is repeated all along the metal until the entire spoon is hot. Have an example sitting in front on the lab table (doesn’t need to be on); a visual.

EXAMPLE OF CONDUCTION A piece of cheese melts as heat is transferred from the meat to the cheese (Contact)

Write down 3 examples of heat transfer by Conduction

Why does metal feel colder than wood, if they are both at the same temperature? Metal is a conductor, 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.

CONVECTION Convection is the movement that transfers heat within fluids and air (gas) Heat is transferred by currents within the fluid or gas Convection = heat transfer through air (gas) and liquid particles Convection moves in a circular pattern(warm rising and cold sinking)

Fluid movement Cooler, more d____, fluids sink through w_____, less dense fluids. ense armer In effect, warmer liquids and gases r___ up. ise Cooler liquids and gases s___. ink

Why is it windy at the seaside?

Examples of Convection: Have you ever noticed that the air near the ceiling is warmer than the air near the floor? Or that water in a pool is cooler at the deep end? Examples: air movement in a home, pot of heating water, wind. Pick one of these examples and draw the circular pattern in your notes. When the water at the bottom of a pot is heated, its particles move faster, and they also move farther apart. As a result, the heated water becomes less dense. A less dense fluid will float on top of a more dense one. Therefore, the heated water rises in the pot. The surrounding cooler water flows into its place. This flow creates the circular motion as seen on the next page, which is known as convection currents.

Explaining Convection Convection currents cause the cooler breezes you experience by a large body of water. These currents also cause the movement of magma within the earth.

Convection questions Why does hot air rise and cold air sink? Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air. Why are boilers placed beneath hot water tanks in people’s homes? Hot water rises. So when the boiler heats the water, and the hot water rises, the water tank is filled with hot water.

RADIATION Radiation is the transfer of energy by electromagnetic waves Radiation does NOT require matter to transfer thermal energy Radiation = Radiates (heat escaping the sun)

Radiation May Come From Other Sources Have you ever sat too close to a campfire while cooking marshmallows? You’re enjoying the warmth ….. only to notice that your skin is really warm?

Examples of RADIATION Fire Heat Lamps Sun