Say you bring in a sealed box full of ice into a warm room. Knowing, thermodynamically, that higher temperature means higher energy of air particles that transfer heat by bumping into one another (don’t kill me for this oversimplification!), how does heat transfer across the hard box sides into the inner space and melt the ice?
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Well the box still transmits energy. Energy tends to flow to any points with lower energy. Kinda like water flows to points with less water. It’s a very simple explanation. But yeah something like that.
Particles in solids also “bump into each other”. They are more tightly packed and interact with all of their neighbors constantly. Imagine a net consisting of small balls connected with springs. If you move one ball, the springs will transfer the movement to other balls. That’s how solids transfer energy within themselves.
Air particles bump into particles on the outer layer of the box, they bump into slightly deeper particles, they bump into even deeper particles and so on, the particles on the inner side of the box bump into the particles of ice / colder air inside the box.
The innermost particles start losing energy after collision with ice (and outermost particles of ice gain this energy). They, in turn, receive some of the energy back from collisions with other particles of the box and so on.
The sides aren’t thermodynamically “hard”; their atoms jiggle like any other atoms. Fast-moving air atoms smash into box atoms on the outside and make them jiggle more, the jiggle is gradually transmitted through the atoms making up the box, finally making the ice atoms jiggle apart and melt.
Heat transfers through the following methods:
1. Conduction — hot atoms vibrate more, bumping those next to them giving them a bit of energy and on down the line.
2. Convection — hot particles (fast moving ones) physically move from a hot area to a cooler area and transfer their energy.
3. Radiation — thermal body gives off electromagnetic energy (black body radiation) that is absorbed somewhere else.
Conduction is the primary heat transfer mechanism through hard (solid) surfaces.
Convection is common in both liquids and and gasses. Not so much in solids since the atoms are by definition not free to move around.
Radiation is the only means of heat transfer through a vacuum. Most of the Sun’s heat transfer reaches us through radiation (although there is a bit of convection via the solar wind).
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