Helppp me which one it is ??

Asample of radium-226 will decay 1/4 of its original amount after 3200years. what is the half-life of radium-226?

In a heat engine of 1000 j of heat enters the system and the piston does 500 j of work what is the final internal energy of the system if the inital energy was 2000 j we have to do all of these down here 1)write the equation 2)list out your know variables 3)plug the numbers into the equations 4)solve 5)write your solution statemtn that includes inital energuy and final energuy added

Which statement best describes what happens when molecular compounds melt