Brachot

Question

The Rav indicated we should should make a bracha on gum. 1) Can we assume that we should make a bracha (blessing) on any small item of food like mints or tic-tacs? 2) What about a bracha achronah (after blessing)? 3) Does it matter how much of the item we have eaten? If so, how much do we have to have eaten to warrant a bracha acronah? 4) What about gum which continues to give flavour which we swallow for quite a while? Thanx!