Question

our nose can identify the aroma of food few meters itself when it is still hot but not the smell of cold ice cream. why?

Answer 1

It's all food hot or normal temperature emits some aroma in the air, the higher the temp the stonger the sent of smell for us. In the cold ice cream the tempteture is too low so aroma emissions are hardly noticeable for our smell sensors.

Answer 2

because diffusion takes place at high temperatures. gases work actively at high temperature rather than low temperature