The weird world of quantum physics and its conservation laws! Which interactions between particles are forbidden and which are possible? Welcome to the world of baryon number, lepton number and strangeness! Meet quarks, exotic baryons, cataclysmic colliders, marvelous mesons and brain twisting bosons. This DOUBLE SIDED worksheet is packed with questions to suit all abilities with plenty to extend more able students. It comes complete with a FULLY COMPREHENSIVE ANSWER SHEET. This is essential A level Physics. Many A level specifications have different requirements for this topic - this worksheets most of them and also allows students to stretch themselves with unfamiliar contexts that their specification may not specifically require but that may crop up in exams. Enjoy.