# Moving in the right circles

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Moving in the right circles

Lava Lamp A lava lamp consists of an enclosed container with two substances of different densities. One substance is wax and the other is a less dense oil. Using heat from a light-bulb in the bottom of the lamp, the oil and wax are heated up.

Geologic Curiosities Can you explain the motion of the wax in the lava lamp over time in terms of energy? In terms of the lava lamp, where is an Endothermic action? Exothermic action?

Connection to Earth Science (Geology)
Energy moves through the earth Either its transported or transferred

Heat transfer Occurs when thermal energy is transferred from a warmer object to a cooler object

Types of heat transfer Radiation Conduction Convection.

Radiation The transfer of energy through empty space or a gas medium is called radiation. No direct contact between a heat source and an object is required.

Conduction Heat transfer by direct contact of particles of solid or liquid matter is called conduction. The energy moves but the medium does not An example is when a spoon heats up in a hot pot of soup.

Convection The transfer of heat by the movement of a heated fluid (liquid or gas) is called convection. The medium moves to transport the heat from one place to another

Does gas convect or radiate heat, energy?
Generally air convects , because it moves to transfer the heat Forms of energy like light and UV Radiate through air, because the energy does not create air currents

The oil and wax movement in a lava lamp is an example of convection

Convection Gain heat, Faster atoms, spread out
Greater volume for same mass = less dense Rise up, and lose heat to other objects Pushed to side by newer, hotter material Cools, loses heat, more dense, sinks

Other examples of convection

Hurricanes

Convection example An example of convection occurs in heating a pot of soup on a stove.

Convection Current Is the flow of less dense hot material upwards and more dense colder material outward and downward Convection cycle or cell is one loop of a convection current

Convection in the earth

Results of convection Heat added to lithosphere may melt the rock, forming magma that flows from volcanoes There is a current created in the Asthenosphere causing rotation in the mat . The crust and lithosphere also undergo pressure to move

Upwelling Region of Astenosphere that the hottest material moves to the top of the layer

Convection Cycle One complete rotation of material that moves from heat source to top of layer and back to source For water, cycle can take seconds For the Earth, cycle can take millions of years

Convection is the engine of the Earth
Heat from deep inside the Earth rises through conduction to the top of the mantle. The material at the bottom of the Astenosphere begins to move upward as it becomes less dense this creates an area of upwelling

Convection cycle continued
3. As the heated material rises to the top of the layer it transfers its heat to the lithosphere/crust and begins to cool, and becomes denser again 4. The cooler material is pushed to the side by hotter material beneath 5. The cooler material sinks towards the bottom of the layer over time 6. Cycle repeated

Final Questions Name at least 3 examples of convection cycles that can happen on earth. How does heat effect density?

Difference in motion Astenosphere bends and slides
Crust/lithosphere breaks and is carried along

Steps to convection in a pot
As soup at the bottom of the pot gets hot, it expands and becomes less dense. The warm, less dense soup moves upward, floating over cooler, denser soup. At the surface, the warm soup spreads out and cools, becoming denser. Then gravity pulls this cooler, denser soup down to the bottom, where it is heated again and begins to rise.

Heated lava lamp When the lamp is turned on, both the wax and the oil absorb energy. This causes the individual molecules of both substances to spread farther apart. But the molecules of wax spread apart much more than the molecules of oil do

Density and heat In eighth grade, you learned that the density of a substance changes when it absorbs energy. As the molecules get more energy, they vibrate faster and farther, decreasing the density. We imagined the molecules to be connected by little springs. When the substance absorbs energy, the “springs” stretch a little farther, increasing the volume of the material. It has no effect on the mass of the material or the size of the individual molecules, only on the size of the sample. If the volume of the sample increases and the mass does not, the density will decrease.

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