1, the components of oil are fatty glycerides, unsaturated fatty acids and saturated fatty acids. Among them, saturated fatty acids are not a big problem, while unsaturated fatty acids will polymerize when stored at high temperature for a long time, leading to oil denaturation. This is not a matter of whether nutrients have been destroyed, but a matter that is harmful to the human body.
2, cooking for a long time will definitely evaporate, not evaporate. When you smell oil, it means that oil molecules are evaporating. The higher the temperature, the faster the volatilization.