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Heat Energy

Page history last edited by PBworks 17 years, 5 months ago

Heat Energy


What is Heat?


Heat is a flow of energy from an object at a higher temperature to an object at a lower temperature.  Heat is different from temperature.  For instance an iceberg has more heat then a boiling pot of water.  That is because heat measures the total amount of energy in all the molecules in something. Since an iceberg is bigger it has more molecules and more total energy.


What is Temperature?


Temperature measures how fast the molecules are moving. So if the temperature is high then the molecules are moving really quickly, if the temperature is low then the molecules are moving slowly. In this case a boiling pot of water has faster moving molecules than an iceberg.  This is because the molecules in an iceberg are moving much slower then the pot of water.


How does Heat Energy Move?


Heat is always trying to even itself out.  If there is two different items of different temperatures, they will eventually have the same temperature. This happens because the two items are constantly bumping into each other. For an example, if you had a very cold cup and you poured warm water into it, then the cup will eventually be the same temperature as the water. The molecules in the water are bumping into the cup's molecules. In the end the warm water's temperature will be lower than before and the cups' temperature will be higher than before.


What is Conduction?

Conduction takes place when energy is passed directly from one object to another. If you stirred a pan of soup on the stove with a metal spoon, you can feel the heat in the spoon. This is because heat is being conducted from a hot area of the soup to the colder area of the spoon.                                                                                                                                                                      


What is Convection?

Convection is the transfer of heat energy in a gas or liquid by movement of currents. The movement of gases or liquids from a cooler area to a warmer area is called convection. One can see convection taking place when we heat up soup in a pan. The warmer soup moves up from the heated area at the bottom of the pan towards the top where it is cooler. Then, the cooler soup moves to take the place of the warmer soup. This movement is in a circular pattern within the pan. Another example is the wind we feel outside. This wind is the result of convection currents. This example is best illustrated when you feel the winds near an ocean. Warm air rises because it is lighter than cold air. At daytime, cool air above the water moves to replace the air rising up as the land warms the air above it. The reverse takes place during night. The surface of the water is sometimes feels warmer and the land, cooler.


An animation depicting convection currents
An animation depicting convection currents


What is Radiation?


Radiation is another way in which energy can be transferred from one place to another. Radiation is energy that travels as electromagnetic waves. The sun is the best source of radiation.  You can feel radiation as heat when it touches your skin.  Radiation can transfer energy from warmer objects to cooler objects. Radiation can travel through empty space.


How do you measure heat?


The main two units are calories and joules. One calorie is equal to 4.18 joules.



Demonstration Explanations

In class, we've done several different heat demonstrations.  In the space below, explain what you think happened in each of them.



 We did a demonstration where we put a cold can of Coke on to a guy's face. After a few minutes we touched the person's face and it was as cool as the can. Then we noticed that the can of Coke wasn't as cold as before. The reason why this happened is because of Conduction. The heat from the person's face transfered into the can of Coke when they touched. That was why the can wasn't as cool as before. The reason why the guy's face was cooler than before was because of themolecules in the can and the face. When the molecules in the cold can touched the face's molecules, they started bumping into each other evening the temperature. So the person's face was cooler than before. That is a demonstration of Conduction and the Movement of Heat Energy.



Burning Dixie Cup







The Water Ferris Wheel

This demonstration was when our class poured cold green colored water into boiling water to see how the green water moved. The green water actually moved in circles going up and down. This was an example of Convention. Convention occurs when when cold liquid or gas pushes the warm liquid or gas upwards. So when the green water plunged down into where the heat was coming from, the green water got less dense and was pushed up by the cold water on top. That was why we saw the green water move in circles.





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