How do we know that a chemical reaction occured

Which is a difference between molecular compounds and ionic compounds? select the correct answer below: question 5 options: molecular compounds typically form between a metal and a nonmetal, while ionic compounds typically form between nonmetals. molecular compounds result from the transfer of electrons between atoms to form ions, while ionic compounds result from the sharing of electrons between neutral atoms. molecular compounds are formed of discrete, neutral molecules, while ionic compounds are formed of large repeating arrays of opposite charges. molecular compounds have high melting points and high boiling points, while ionic

What substance has a mass of 9.5g and volume of 2.1cm^3

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