The mathematics of weight loss | Ruben Meerman | TEDxQUT (edited version)

Mrs Heckman and I were having a discussion one time about what happens to the fat - or whatever else - you burn when you lose weight. My contention at the time was that the fat was turned into carbon dioxide and water vapor which was eventually exhaled from your body - mostly as carbon dioxide but less as water vapor.

I don't, honestly, remember what her contention was...because it was wrong.

I do love the explanation of what the arrow (at about 5:00) actually means.

In the long run, it's just conservation of mass, and when we're talking about 'invisible' gases, it's an incredibly slippery concept for being so simple.

In all honesty, if my students could successfully answer the question he asked of the sunbathers on Bondi Beach, I'd be pretty happy about their conceptual understanding of chemistry.

There's a flip side to all this, and I'll post about that next week.

How Not to Put Out a Metal Fire - with Steve Mould

I remember watching WGN a couple of decades ago about a fire at a metals recycling company in Chicago (maybe this one?) The thing that fascinated me at the time was watching the firefighters spray water on the fire, have it explode, and repeat the process a couple more times. The fire chief at the time - in my deep memory, at least - said something to the effect that they knew the explosion was likely but that they were trying to dump enough water on all at once to cool the fire enough to stop the burn. Not enough water = explosion, though.

In the above video - the Royal Institute - Steve Mould shows why magnesium fires are such a bear to put out. They don't - as the article linked above says - 'produce their own oxygen', but they do tear oxygen off of carbon dioxide and water. Once that happens, then, the fire allows the hydrogen and oxygen (from water - or oxygen and carbon (from carbon dioxide) to react with the magnesium or with each other producing an even hotter flame.

Hmmm...seems magnesium's active or something.

(And I don't think - at 2:55 - you 'can actually see [the beaker filling with carbon dioxide]', Steve. My understanding is that carbon dioxide is invisible. What I think you're seeing is fog, condensing water vapor due to the coldness of the dry ice.)

Bagged Water in Space Has Weird Bubbling Behavior

I'll admit to being a sucker for just about any 'in space' video.

Here we see - and the space.com article explains - air bubbles not separating from the water surrounding them in a plastic bag 'in space'.

It looks impossible but makes absolute sense because it's not the IMFs that separate water from air on Earth's surface but rather the pull of gravity. Gravity pulls more strongly on the more dense water, so the water goes down and pulls together to 'push' the air upward.

No gravity, no pull...no buoyancy...no separation.

How cool is that?