Sorry if the question is poorly worded. I’m not even totally sure what I’m asking. If I put my warm hand on a cool counter top, the part under my hand slowly warms up. Is my hand pushing the heat out to make the two the same temperature or is the counter top pulling the heat out of my hand? Are both objects working together?
Heat can be transferred in any of four ways: convection, conduction, thermal radiation, and evaporative cooling. When you come into direct contact with the counter, or any object for that matter, conduction is the way it happens. Heat flows from a warmer object to the cooler object.
Ok so it’s my hand pushing out the heat, not the counter pulling heat from my hand?
It’s the wiggling of the molecules in your hand that give the feeling of heat. The more they wiggle, the hotter it feels. When you press your hand to the counter, the movement of the wiggling molecules of your hand get transferred to the molecules of the counter. Now the molecules in the counter under your hand are wiggling more, which means it has more heat. The molecules in your hand slow down a bit when their wiggles get transferred to the counter, which means your hand feels cooler.
Heat is always pushed, both ways. The hotter an object is, the more heat it pushes. Once two objects are the same temperature, there’s the same amount transferring both ways, for no net flow.
And the molecules in your hand have lost that energy, so they feel cold until something (your body’s processes) warms them back up again.
Energy always wants to equalize.
Stuff is made of particles. Be it atoms, molecules, or whatever (depends on the thing, metals versus other stuff mostly.) Particles vibrate - the energy embodied in these vibrations is what gives stuff heat. More heat, more vibrations.
Particles making up your hand are, on average, vibrating faster than particles making up the cup. The particles of your hand are bumping against the constituent particles of the cup, and they bang together and rebound, and behave, to a very good approximation like ideal billiard balls. On average, on any given banging together, the faster moving particles deposit more energy into the slower moving ones than goes the other way. So, on average, energy flows from the thing made of faster moving (hotter) particles, to the thing made of slower moving particles. Over time the exchange evens out, and both things reach an equilibrium.
The heat in your body is flowing to the counter via the molecular contact between your hand and the counter, so it is from you to the cooler counter.
Thank you for the replies. I was waiting for the kettle to boil, leaning on the counter and I just got to wondering how the heat goes from me to the counter. I tried googling it but wasn’t getting anywhere and I knew I’d get the answer here.
The phrase you were looking for is heat transfer.
In some sense, there is no such thing as cold, cold as just the absence of heat (particle motion). I also remember my high school chemistry teacher being fond of saying ‘there is no sucking in chemistry.’ Forces (like air pressure) are always pushing forces. There is no such thing as a sucking force*.
*Except for (insert your least favorite political figure here. Just kidding, don’t.)
It’s somewhat easy to understand wiggling atoms touching and transferring energy that way, but that’s not the only way heat can transfer. Something that’s not obvious is that wiggling atoms can throw off heat through light energy, called thermal radiation. You’ve probably heard terms like infrared heat, white hot, and red hot. These are all describing how hot objects can produce light, and that light can transfer heat from one object to another. It’s from the electrical forces of the wiggling atoms interacting with each other and feeling resistance. Sort of like if you wiggled two magnets with the same sides facing each other. You can feel the resistance as you move the two magnets close to each other. The same sort of resistance is felt by the electrical fields of the atoms, and that resistance produces photons.
If you put your hand near a hot object without touching it, like putting your hand near a hot kettle, you can feel the heat even though your hand isn’t touching it. Some of that is from hot air molecules, but some of it is from the light produced by the heat of the kettle being absorbed by your hand. If you put your hand near the counter without touching it, this light energy from your warm hand will transfer heat from your hand into the counter to warm it up. And since it’s light, it doesn’t even need air. It can transfer heat even through a vacuum. That’s why we can feel the heat of the sun. The light energy travels through space and is absorbed by matter here on Earth.
That’s crazy!
I’m currently down the worm hole of convection vs conduction.
There is another contributory factor: When the thermoreceptors in your skin sense a cold object, they trigger a reaction that attempts to warm the cold area.
The transfer of heat from the body to very cold metal can be rapid enough to cause burns.