KS3 Bitesize – Elements, Compounds & Mixtures & Separation Techniques (a 14m 21s video); Elements, Compounds & Mixtures (a video covering Elements, Compounds & Mixtures and the Periodic Table) and Chemical Reactions (a video covering Word Equations, Oxidation & Combustion Reactions, Decomposition Reactions & Helpful & Unhelpful Reactions).
Atoms, Molecules, Elements & Compounds (Wan2tlkScience?), a 9m 18s video; Scientific Eye – Atoms & Molecules (19m); Science in Action – Mixtures (19m).