1. Introduction: One Acid, Five Different Partners
You already know how to spot an acid. It tastes sour, it turns blue litmus red, and you have met a few by name — HCl, H₂SO₄, HNO₃, and the citric acid inside a lemon.
Now the question changes. Not what is an acid, but what does an acid DO when you put something into it?
Drop a piece of zinc into dilute HCl and it fizzes. Drop a piece of chalk in and it also fizzes. Two fizzes that look identical to the eye — but the gas coming off is not the same gas. If you cannot tell those two apart, you will lose marks on a question you actually understood.
Here is the plan. An acid meets five kinds of partner: a metal, a metal carbonate, a metal hydrogencarbonate, a metal oxide, and a base. Each meeting has a fixed pattern. Learn the five patterns and you can write the products of any acid reaction in the syllabus without memorising a single extra equation.
Stop scrolling. Zinc in acid fizzes. Chalk in acid fizzes. Guess in your head: is the bubbling gas the same in both?