A 19m 18s video on Chemical Reactions from Scientific Eye:
Science in Action – Chemical Reactions – a 19m video; Chemical Reactions (Wan2tlkScience?), a 4m video.
KS3 Bitesize foundation level – Chemical Reactions – a video covering Word Equations, Oxidation & Combustion Reactions, Decomposition Reactions & Helpful & Unhelpful Reactions.