18. What do you call a change in state from a liquid to a gas?

What is the length x of the side of the triangle below? (hint: use the cosine function)

In a heat engine if 1000 j of heat enters the system the piston does 500 j of work, what is the final internal energy of the system if the initial energy was 2000 j? 1. write the equation 2.list out your known variables 3.plug the numbers into the equations 4.solve 5.write your solution statement that includes initial energy and final

I’ve been stuck on this for a while