Hydrogen, carbon, and gold are all examples of? chemical reactions elements molecules compounds

In a heat of an engine, if 700 j enters the system, and the piston does 400 j of work what is the final internal (thermal) energy of the system if the initial energy is 1,500 j

To calculate percent by mass, use the equation below: calculate the percent by mass of each element. %n = % %h = % %o = %

When a beta particle is emitted, the mass number of the nucleus a. decreases by one b. increases by one c. remains the same d. decreases by two