What does it mean when substance are move against a concentration gradient?

It means they are diffusing or going from an area with a higher concentration to an area of a lower concentration of that same substance. 

Ans. : frostbite is when exposure to cold temperatures causes freezing to the skin or other tissues. it most commonly affects the hands, feet, and face. the longer areas are exposed to cold, typically the worse the frostbite. the water temperature used for rewarming a frostbitten part should be : (102 -105) f degrees.

As cooking food that has to go in the oven