Heat Transfer: Conduction, Convection, and Radiation PDF

HEAT TRANSFER: CONDUCTION, CONVECTION AND RADIATION ❏ Temperature: average kinetic energy of a group of atoms in a sample of matter ❏ Measures the “hotness” or “coldness” of an object ❏ Can use the Celsius, Fahrenheit or Kelvin scale ❏ Commonly use a thermometer; works by thermal e...

HEAT TRANSFER: CONDUCTION, CONVECTION AND RADIATION ❏ Temperature: average kinetic energy of a group of atoms in a sample of matter ❏ Measures the “hotness” or “coldness” of an object ❏ Can use the Celsius, Fahrenheit or Kelvin scale ❏ Commonly use a thermometer; works by thermal expansion VOCABULARY  Heat: transfer of energy from one object to another based on differences in temperature ○ Use a calorimeter ○ SI unit is the Joule Specific Heat (Heat Capacity); amount of energy required to raise the temp. of a sample of matter 1 degree ○ each substance has its own specific heat value Vocabulary  Thermal Energy: energy within a system that is created by the random motion of atoms and molecules. ○ As motion increases, more energy is produced ○ This energy is transferred in the form of heat ○ based on size and temperature Which has more thermal energy? A glass of water at 60 degrees Fahrenheit or a pond at the same temp.? Conductor: material that readily transfers heat ex. metals, especially copper and aluminum Insulator: Material that does not readily transfer heat ex. fiberglass, foam Thermal Energy Transfer ◻ Thermal energy transfer is heat moving from a warmer object to a cooler object. This is known as thermal energy transfer. 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 = CONTACT 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. EXAMPLE OF CONDUCTION ◻ A piece of cheese melts as heat is transferred from the meat to the cheese (Contact) CONVECTION Convection is the movement that transfers heat within fluids and air (gas) Heat is transferred by currents within the fluid or gas Convection = VENTS (through air and liquid particles) Convection moves in a circular pattern 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. 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 1. Fire 2. Heat Lamps 3. Sun Uses of the Principle of Heat Transfer HVAC systems refrigerators cooking weather patterns regulation of body temp. thermal sleeping bags and coats