Pure Substances vs Mixtures (Middle School Science)

From a channel Lumen includes in full: Every sampled title is a plainly descriptive curriculum topic, and every transcript opens with stated learning objectives and then teaches the material directly, including definitions, equations and worked examples, with no hooks, hype or entertainment framing. The About text points to a companion practice website, but none of the sampled lessons is promotional; they are complete standalone lessons whose primary aim is understanding. Any stray promo, channel-update or Shorts uploads can be caught by title patterns.