Req 4b — See Tracks in a Cloud Chamber

A working cloud chamber feels like science fiction the first time you see it. Out of nowhere, thin white streaks appear and vanish in the chamber. Those streaks are evidence of ionizing particles moving through vapor and leaving a trail of ions behind them.

What is happening inside the chamber

A cloud chamber contains alcohol vapor cooled until it becomes supersaturated. That means the vapor is ready to condense but needs a trigger. When radiation passes through the chamber, it ionizes atoms along its path. The vapor condenses around those ions, making a tiny visible trail.

Different particles can leave different-looking tracks:

• short, thick tracks may suggest heavier particles
• longer, thinner tracks may suggest lighter or faster particles
• sudden bends or branching can hint at interactions along the way

You do not need to identify every track perfectly. What matters is explaining that radiation leaves behind ionization, and the vapor makes that invisible process visible.

If you want to model radioactive decay with data instead of vapor trails, the next experiment is a great fit.