TOASTER BALLOONS
Get your head around the thermal
expansion of air and you'll have no
problem flying bin bag balloons with
a toaster.
These notes accompany the hands-on video guide and detailed explanation and safety tips
at: bbc.co.uk/bang/handson
Safety: Adult supervision required. Toaster will become hot – please do not touch toaster or
allow the plastic bag to touch it. Allow toaster to cool down between each balloon.
WHAT:
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HOW:
Put toaster on heatproof surface.
Turn on toaster for approx 1 minute.
Open top and bottom of box and place over toaster.
Open bin bag and place over top of box and lightly hold in place.
Wait 15–20 seconds and the bag will start to inflate and lift.
WHY:
The toaster warms up the air that's in the bag. Most things expand when they get
warmer, including the air inside the bag. The trapped air wants to fill a larger
volume and the bag puffs up. Once the bag can't puff up any more, expanding
air is instead forced out of the bag's open end. The bag now has the same volume
of air in it, but that air weighs less than when it was colder (its density is
reduced). So a litre of warm air inside the bag weighs less than a litre of room air
outside the bag. A pocket of air surrounded by something more dense has
buoyancy and will rise, just like an air bubble underwater. The buoyancy of the
warm air is enough to lift a very light plastic bag.
TIP:
Try different types of bag to see which one flies the highest.
Electric toaster
Cardboard box – at least 50cm tall and big enough to go over the toaster
Small, cheap bin bag to fit over box
Heatproof surface