Why is energy needed to change the state of matter of a substance even though temperature doesn't change?

Because without energy the cells are not able to complete their job correctly. :)  Hope that helped.

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.