One of the key things I learned when first teaching this subject is the annoying tendency of children to say “but why should I use an equation if I can just solve the problem in my head?”
To combat this, I have created several sequences of lessons in which the focus is solely on forming an equation, without solving it. Most of the problems do not even have a unique solution, which removes all temptation to solve them. I also take the opportunity to distinguish clearly between expressions and equations to help embed this vocabulary.