In this Prodigies Music Lesson, Mr. Rob takes intervals a bit further by talking about the quality of an interval--major or minor.
The quality of the interval changes the sound drastically, regardless of still being second intervals.
Mr. Rob discusses the Major seconds: C & D, D & E, F & G, G & A, A & B and the Minor seconds: E & F, B & C and helps students hear the difference between the major second and the minor second.