Why is that the concept of heat or temperature is only related to IR (Infrared Radiations), when the IR are also just like any other EM waves e.g. visible, UV, Radio etc. ?

 

What accounts for the enhanced movement of liquid molecules when they are heated. I can imagine electrons going to a higher energy orbit on being exposed to say IR, but am not able to figure out how the whole molecules can start scurrying around on being heated ?

heat at room temperature(around 293K) is mainly in the IR spectrum. that is why it is related to IR so much. though blackbody radiation is found in all frequencies and can be described as thermal radiation.if it is above 800K or so it will emit a significant abount of visible light and if it is at 6000K it's main emmission will be in the green part of the spectrum.

Why is that the concept of heat or temperature is only related to IR (Infrared Radiations), when the IR are also just like any other EM waves e.g. visible, UV, Radio etc. ?

 

It's not.

 

The misconception arises because a lot of the blackbody spectrum is in the IR for ~room-temperature items, as i_a notes.

 

What accounts for the enhanced movement of liquid molecules when they are heated. I can imagine electrons going to a higher energy orbit on being exposed to say IR, but am not able to figure out how the whole molecules can start scurrying around on being heated ?

 

 

Temperature is related to center-of-mass kinetic energy of atoms and molecules. That's how it is defined.