How is the (Delta)Hfusion used to calculate volume of liquid frozen that produces 1 kJ of energy?

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.

What is the importance of interlocking the fingers and rubbing while washing hands? the palms are the dirtiest parts of the hands. the spaces between the fingers get washed. the backs of the hands get washed. the fingernails are the dirtiest parts of the hands

Which is an example of a highly unstable isotope that is often used in fission reactions?