In the U.S. the Memorial Day weekend marks the unofficial start of summer--and the beginning of barbeque season. As you sear the meat and toast the buns, have you ever wondered why grilling beats boiling? Or why ketchup and mustard tend to separate, but mayonnaise does not? Or why a pickle lasts so long? 

Our friends at NBC Learn are producing an ongoing set of videos explaining the basic chemistry behind everyday items as part of its  Chemistry Now effort. (Check out the chemistry of chocolate .) The videos include a series on the hamburger and its symbiotic accompaniments--all part of the celebration of the International Year of Chemistry 2011 .