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When we supply heat, molecules move away from each other. When I searched on google for why this happens

(https://byjus.com/question-answer/how-does-heat-energy-help-particles-overcome-forces-of-attraction/ )

-I found that on supplying heat, heat energy is converted into kinetic energy which is stronger than the force which binds molecules, and hence molecules start moving. But why heat energy converted into kinetic energy ? Heat is also a kind of energy, then instead of making molecules move away from each other, why isn't this energy used to make bonds between molecules even stronger ?

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  • $\begingroup$ Your first statement (“When we supply heat, molecules move away from each other.”) isn’t always true; it holds only for materials that (1) expand with heating and are (2) allowed to expand. Can you clarify whether you’re asking about a temperature increase or a phase change such as boiling? Both can occur from heating, and the associated details are very different. $\endgroup$
    – Chemomechanics
    Commented Aug 3, 2022 at 17:28
  • $\begingroup$ I am asking about temperature increase $\endgroup$
    – apk
    Commented Aug 3, 2022 at 17:40
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    $\begingroup$ The misconception may be that bonds store energy (and therefore that adding energy strengthens them). They do not. Bond release energy when they form; they represent a (preferred) state of low energy—indeed, that’s why they form. Adding energy tends to break them. $\endgroup$
    – Chemomechanics
    Commented Aug 3, 2022 at 18:02

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Heat energy is kinetic energy. We take gas molecules as an example: Adding heat energy to a gas causes the gas molecules to speed up and hence collide with each other with greater force. This causes the molecules to (on average) move farther away from one other between collisions as the temperature of the collection of molecules is increased.

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  • $\begingroup$ Thanks but I haven't yet clearly understood why heat energy is kinetic energy. Let me try to explain my doubt as clearly as possible. Heat is also called thermal energy. Heat is the form of energy that is transferred due to the difference in temperature of two bodies. As temperature increases, molecules start moving, and that is why we say heat is a measure of kinetic energy, right ? But then the question arises, why do molecules start moving at increasing temperature? Maybe it's a very basic level but still, It will be very helpful if someone could provide a detailed insight into this! $\endgroup$
    – apk
    Commented Aug 4, 2022 at 7:09
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    $\begingroup$ if we look at a sample of say hot gas with a magic microscope, we see that each gas molecule is zooming around at high speed and bouncing off the walls of its container and off of other molecules. we assign a temperature to the hot gas based on the average kinetic energy of the molecules in it. in this sense, temperature means molecular movement, and the only time a molecule is not moving is at a temperature of absolute zero, at which all molecular motion stops. $\endgroup$
    – niels nielsen
    Commented Aug 4, 2022 at 22:55

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