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A hot object has fast molecules, i.e. molecules with high kinetic energy. When it touches a cool object (which has slow molecules), its fast molecules randomly whack into the slow ones and make them move faster, increasing their kinetic energy.

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Heat is the kinetic energy of particles. The more they move, they more they bump into other particles and knock them around as well, "heating," them up.

i could be wrong but i think the ops question is something like this....

if you put a flame under a piece of steel, the particles in the steel move around faster, which we feel as heat.....but why does the flame make them move faster?

Mostly conduction, meaning the particles of the hot gases of the flame are moving very fast and keep bumping into the steel particles.

The vibrations, rotations and general movement of particles will always contain some kinetic energy. We can measure this general vibration as a temperature of the particle system.

When you heating something, say water on a stove, the energy from the stove is being conducted through a vessel into the water, adding energy into it. The particles in the metal then vibrate faster and faster, and those metal particles in contact with the water will then impart energy to the water particles, heating the water.

Heat is the transfer of energy from a hot object to another. The temperature of an object is a measure of the typical kinetic energy of the particles.

One big issue, is that energy is an abstraction

It tells you a lot of useful things, with very simple math, but you can't ever measure energy directly. So you should give up the idea the energy is a actual "thing" but more of a "label".

So heat, is just the label that we give to a body whose particles move in a disorderly fashion. The more they move the more heat they have. (Actually to be precise heat is how much of the movement of the particles is/can be transferred to another body, but the point stands)

If you consider one single particle, it can't move disorderly, because relative to itself it always moves straight, so for a single particle we prefer to use the label kinetic energy, because a body whose particles move in an orderly fashion is simply a moving body and not an hot one.

Once again, heat and kinetic energy, are functionally the same thing, just two different names for two facets of the same phenomenon.

Heat is just another word for transferring kinetic energy. Temperature above absolute zero is just the random, kinetic energy of atoms. Heat is the process by which the kinetic energy of one thing is transferred to another. How the heat (energy) is transferred depends on circumstances. Radiation, convection, conduction are some ways, but in every case kinetic energy is transferred from one thing to another.