Fountain Experiment — Solubility of HCl (Explainer)

A guided, narrated version of the HCl fountain experiment that separates the two conclusions students routinely conflate. It runs the demonstration twice: first with plain colourless water — proving only that HCl gas is enormously soluble as the pressure collapses and the atmosphere drives the fountain up — then again with blue litmus, whose turn to red proves the dissolved gas is acidic. Step-by-step narration (multiple voices) walks through each stage so the 'solubility versus acidity' distinction lands before students experiment for themselves.