# Modeling Heat Movement

Heat is in constant motion. It flows from warmer areas to colder areas until an overall equal temperature is established. Heat moves from one place to another in three ways. The movement of heat from a warmer object to a cooler one is called heat transfer. There are three methods of heat transfer: conduction, convection, and radiation.

Conduction is the movement of heat energy through a substance or from one substance to another by direct contact of atoms and molecules. Heat moves directly from one molecule to another. The heat energy speeds up the movement of the atoms and they collide with other molecules setting them into faster motion. This goes on until all the molecules are moving around faster and the entire object becomes hot. What you feel is heat moving along the object from the source to the end. Have you made a cup of hot chocolate? As the hot chocolate sits in the mug, the mug begins to get hotter. If you leave a metal spoon in the cup, it will heat up also. Where will the spoon get hot first? Where will it be the coolest? What will happen to the spoon after some time if it is left in the cup? Can you think of other examples of conduction?

Convection is the transfer of heat in a liquid or gas as groups of molecules move in currents from one region to another. Warm air is less dense than cool air. Therefore, warm air rises and cool air sinks creating a convection current.

Hot air balloons use this principle to lift off the ground. The air in the balloon is less dense than the surrounding air and rises to lift the balloon off the ground.

Water is also heated by convection. When water is heated in a pan, the water near the burner is heated first. The heat causes the water to expand, it becomes lighter, and it rises to the top of the pan. The heavier, colder water near the top sinks down, pushing the hot water up. This continues until all the water is evenly heated. You can see the path of convection current if you watch spaghetti cooking in a pot of boiling water. The spaghetti will move in a circular path around the edge of the pot as the water boils.

Heat is what we have when molecules are in motion. The sun creates a lot of heat! As the heat travels through space, it is actually converted into electromagnetic energy or Radiation.These waves travel through space and the atmosphere of Earth. When these waves hit an object on Earth, the energy passes into the object, and it becomes heated.

Other familiar forms of heat transfer by radiation include: heat you can feel around an open fire or a candle flame, the heat near a hot stove, and the heat given off by an electric heater.

You can model the movement of molecules as heat energy moves in the following activities. The following activities require careful, unhurried observations.

Materials:

• Beaker
• Water
• Ice
• Cup
• Hot plate
• Wooden spoon
• Plastic spoon
• Metal spoon
• Small uncooked noodles
• Bunson burner

Safety concerns: Be sure to keep all eye and heat safety rules. As with all science lab activities, the most important safety rule is to follow all teacher directions.

Procedure:

Activity #1

1. Fill your beaker 3⁄4 full of water and place it on the hot plate.
2. Heat to boiling and add 10 to 15 noodles.
3. Wait two minutes and write your observations in your science journal.

Activity #2
1. Pick up the three spoons. Describe their temperature in your science journal.
2. Fill your cup 3⁄4 full of ice-water.
3. Place the spoons into the cup of ice-water and let them sit for 3 minutes.
4. Take the spoons out of the water and describe their temperature in your science journal.

Activity #3
1. Light a bunson burner.
3. Slowly bring your hand straight down toward the flame, stopping AS SOON as you feel heat transfer taking place

Analysis:

1. What kind of heat transfer did you demonstrate in each of the activities?
2. Describe the transfer of heat in activity #2. (Where did the heat come from and where did it go?)
3. Explain the movement of the macaroni.
4. Give an example of each type of heat transfer. (Come up with your own examples, not the ones used in the text)

Review Science safetey rules here.

Get the plug-ins: , and . (The QuickTime plug-in is needed to play sounds and movies correctly.)

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1. The title of the activity