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Flashcards by Kirk Johnson, updated more than 1 year ago
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| Question | Answer |
| Types of Heat Transfer | Thermal (heat) energy can be transferred in three different ways: conduction, convection, and radiation. |
| Conduction | Occurs in solids where heat is transferred from the hot to the cold end. The particles can pass the thermal energy to each other; electrons can leave their atoms and move freely. The particles vibrate continuously and when they are heated they vibrate more therefore giving off more kinetic energy. The electrons transfer this and collide with other particles consequently spreading the heat across the solid. Metals especially are very good conductors, however gases and non-metals are not (but are good insulators as they prevent heat from leaving.) |
| Convection | Occurs in fluids (i.e: liquids and gases. Fluids are states of matter that can flow and their particles can move around.) When the particles are heated, they expand. Expansion is when the particles are heated and they vibrate quicker, so although the particles don't change in size the gaps in between them do, thus making the substance larger. This means the particles get less dense and rise up into the air, taking the place of the colder particles. These in turn get heated and once the above particles cool down and are heated once more, this becomes a convection current. |
| Radiation | Radiation doesn't require particles to transfer heat and is how the Sun gives the Earth heat energy, as the electromagnetic waves in radiation can travel through the vacuum of space (and any vacuum. For example, in a vacuum flask, only radiation can heat the flask; conduction and convection cannot.) Matt black objects are good absorbers and emitters of radiation; silvery shiny surfaces aren't (because they are good reflectors of radiation.) |
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