Convection and the Mantle Notes

Types of Heat Transfer When an object heats up, particles in the object have more energy and move faster. The energy can travel, or transfer from a warmer object to a cooler object. Energy NEVER transfers from cooler to warmer.

Slower Faster

Types of Heat Transfer Radiation is the transfer of energy through space. For example, sunlight travels through space by radiation and warms Earth’s surface. Radiation also explains why your hands get warm when you hold them near a fire. Radiation DOES NOT require a medium to transfer its energy.

Types of Heat Transfer Conduction is the transfer of heat between objects that are touching. If you touch a hot pot, heat travels from the pot to your hand by conduction.

Types of Heat Transfer Convection is the transfer of heat by the circular motion of particles in a fluid (gas, liquid, plastic solid). Moving particles transfer heat throughout the fluid. This is where the phrase, “warm air rises,” is applicable. BUT it needs to be rephrased to state, “warmer air rises, cooler air sinks.”

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Convection Currents The movement of particles due to the transfer of energy by convection is known as a convection current. Multiple current can occur within a single fluid. ONE current is known as a convection cell.

Convection Currents A convection current starts when there are differences in temperature and density of a fluid. Density is the amount of mass in a given volume of a substance (how tightly packed the particles are). A high-density substance feels heavy for its size. soccer ball vs. bowling ball

Convection Currents Which is less dense: hot air or cold air? Which is less dense: hot air or warm air? Because particles move faster when they are warmed up, they also tend to spread out, therefore the warmer a fluid becomes, the less dense it will become as well.

Convection Currents Suppose you put a pot of soup on the stove. The soup at the bottom of the pot will get warm first. Because it is warmer, the soup at the bottom of the pot is less dense than the cooler soup above it. So the warmer soup rises. At the same time, the cooler, denser soup sinks to the bottom of the pot.

Convection Currents The cooler soup now at the bottom gets warmer, and the process repeats. A constant flow of particles begins. Warmer soup keeps rising, and cooler soup keeps sinking. This movement of particles transfers heat throughout the soup. This is the same process that occurs with cooling houses from the ceiling and heating them from the floor.

Convection Currents in Earth The heat inside Earth causes convection currents in the mantle and outer core. Convection currents inside Earth are like convection currents in a pot a soup. Hot materials rise to the top, and cooler materials sink to the bottom.

Convection Currents in Earth Convection currents in the mantle move very slowly. This is because the mantle is made of solid rock. Remember, Earth is like a giant magnet because of currents in the outer core. Those currents are convection currents.