It stays constant, because it's using that energy to change state
A gentle slope requires less force over a longer distance as compared to steep slope.
Explanation:
Mechanical advantage of a slope is equal to the ratio of length of slope and the height. A steep slope has shorter length as compared to a gentle slope for the same height. Therefore, mechanical advantage of a gentle slope is more than that of a steep slope. Hence, a gentle slope requires less force over a long distance than a steep slope.
This is true due to the reaction that happens from water evaporating and leaving the sugar crystals behind to form.