Physical properties are those which can be observed without any change in composition of the substance. Hence, a is the answer.
This equation represents a single replacement reaction. Single replacement reactions consist of one element reacting with one compound on the reactant side (left side of the equation) and they form one new element and one new compound on the product side of the equation (right side).
I would say that you should wear a lab coat, safety goggles, and gloves
when the teacher says so - not everything in a lab is dangerous, so
there is no need to always wear these. But when the teacher says you
should - then you should.