Question

why the hot food smell coming fast and cold food very slow

Answer 1

this is coz hot air expands on heating and hence able to reach faster whereas cold air cannot do the same.

Answer 2

as the hot air has less density(food heats the air in its surrounding), it can raise up quickly and reach different parts but cold food with presence of dense air above it cannot travel fast (hot air has less density and cold air has more Density)