Why do blown bubbles last longer with soapy water than with plain water?

Answer: Soap changes surface tension and helps stabilize the thin water film

Soap changes surface tension and helps stabilize the thin water film ✓ — Soap lowers water’s surface tension and helps a thin liquid film resist breaking. Its molecules gather at the film’s two surfaces, with their water-loving ends in the water. Plain water can form fleeting bubbles, but the films usually break much more quickly.

Soap produces gas that keeps inflating the bubbles — Soap does not generate the gas inside these bubbles. The air comes from blowing or mixing; soap helps the surrounding liquid film last longer.

Soap makes water lighter so the film stops falling under gravity — Soap does not make water weightless or remove gravity’s effect on the film. A soap bubble still contains liquid with weight; making that liquid a thin, stable film is different from making it lighter.