Convection, Conduction, and Radiation Heat Transfer

Review of Density  Warmer temperatures = less density  Cooler temperatures = higher density

Density and Motion How does this happen? Look at the example: If these 2 arrows come together, will they move? Why or why not? 10 No movement!

Density and Motion Now look at this example. If these 2 arrows came together, what would happen? 105 Movement! The values are not equal & the movement will be in the direction of the bigger force

Density Poem “Motion will go from high to low” Meaning: the molecules will go from where there are a lot to an area where there are few Equilibrium: when molecules are equal on both sides (no movement!)

Don’t forget!  High amount of molecules = cooler temperatures  Low amount of molecules = warmer temperatures

Motion and atmosphere  Cool air sinks (more dense)  Warm air rises (less dense) Motion: Creates a circular motion: heats up goes up, cools off comes down, heats up goes up, cools off comes down

Motion in water  Cool water sinks (more dense)  Warm water rises (less dense) Motion: Creates a circular motion: heats up goes up, cools off goes down, heats up goes up, cools off goes down

Motion under the Crust  Cool magma sinks (more dense)  Warm magma rises (less dense) Motion: Creates a circular motion: heats up goes up, cools off comes down, heats up goes up, cools off comes down

What causes those fluids to heat up? Radiation (aka a heat source) Natural Radiation: The Sun, the center of the earth, fire Artificial Radiation: hot plate, burner on stove, candle

Conduction  When the radiation gets transferred to an object, that is called conduction  2 objects must be in contact with each other  Objects can be as small as electrons Examples: touching a hot spoon, sitting on leather seats in the summer, feeling the counter when the sun is out

Convection Currents  This is the circular movement of the heat transfer  This is an action, a verb, a “doing”  Molecules will flow to different levels of concentrations: from high to low

Which temperature has more molecules in a given space?  Cooler/Cold  Cooler temperatures = increased density  Think about the molecules packed together in ice  What type of temperature outside will have greater density: hot weather or cold weather?

Which temperature has less molecules in a given space?  Warmer/hot  Increased temperatures = decreased amount of molecules in the same area  Think about how the molecules would look like in a gas  all spread out  What type of temperature outside would have lower density: hot weather or cold weather?

Summary of CCR:  Radiation: EM radiation from the Sun heats up the ground or water  Conduction: transfer of heat to touching molecules  Convection: the different densities of temperature create a circular movement: from high to low