Summarise the first form of Aquinas’ argument for the existence of God

Things don’t change themselves, they are always changed by something, for example; a marble block into a statue. In order for change to occur, the mover must be in the new state in order to change the object - this mover is called the efficient cause. An infinite regress of movers is impossible, therefore there must have been a first efficient cause to start the chain of movers. In conclusion, God is the unmoved mover which started off the chain of movement.