What is an acid and what is the difference between and strong and weak acid

An acid is a proton donor. The acid molecule may have one or more protons that it can lose depending on its structure, however generally the second proton is much less acidic (meaning that it is lost much less readily). An example of this is the strong acid H₂SO₄. When dissolved in water, this acid loses one proton to form HSO₄^- Acids can differ in strength, one factor affecting acidity is the polarity of the bond between the Hydrogen and the atom it is bonded to. A weak acid will partially dissociate in water whereas a strong acid will fully dissociate. An example of a weak acid is: ethanoic acid (also known as acetic acid) which has the formula: H₃CCOOH An example of a strong acid is: HCl HCl is a particularly strong acid because Chlorine, like all the halogen atoms, is very electronegative and as a result, the H-Cl bond is very polarised with a partial positive charge on the H and a partial negative charge on the Cl. In water, HCl forms entirely H⁺ and Cl^-.