When copper (Cu) combined with Tin(Sn) they make bronze. The product which these two elements form when combined with each other is called "Alloy" which is the Bronze that was mentioned in the question.
Why is this done?
This is done to produce an "Alloy" and alloy is usually used because it is stronger.
Industries prefer alloy in situation where they need strongness that they cannot find in a single element.
A physical change is basically a body change so like if a crayon is solid then sits in the sun for a long time it melts away that’s a physical change because it changes its physical appearance
