Is lifting gas? That’s pretty cool.

Technically yes, but practically no. Air is 78% nitrogen. Nitrogen is 3.3% lighter than air. Helium is 86.2% lighter than air. Hydrogen is 93% lighter than air.

How much does that matter for party balloons, though? It's still buoyant.

I feel like people really need to learn basic physics.

The gas inside a standard party balloon is generally compressed 3% to inflate the balloon. This wipes out even the theoretical buoyancy of nitrogen. And trust me, there was never any practical buoyancy to begin with. You’d need a ridiculously large balloon in a room with impossibly still air and impossibly null thermal gradients to even measure the buoyancy of nitrogen vs air. The buoyancy of nitrogen vs air would never be perceptible to human senses in any real-world setting.

It would be the same as just filling the balloon with air.

> I feel like people really need to learn basic physics.

I'm 20+ years out of college and I asked a question specifically because I was unsure. Give me a break. I'm sorry if "party balloon buoyancy physics" wasn't the part of my college classes that stuck with me.

A spherical balloon 20cm in radius is displacing 41g of air. Even ignoring compression (which I don’t know enough to quantify the effects of, except that it will make the numbers more unfavourable), nitrogen’s 3.3%-lighter gives you a budget of only 1.35g for the balloon. I believe balloons hare heavier than this, so the balloon will still sink (a little more slowly than an air-filled one, but I’m not sure how noticeable the difference will be).

> which I don’t know enough to quantify the effects of

You probably do, actually! People constantly underestimate the grand utility of their basic education.

At near-atmospheric pressure and typical ambient temperatures, the ideal gas equation (PV=nRT) from introductory physics works very well and indicates that a 3% overpressure would make gases 3% more dense (linear direct proportionality). At some threshold of high pressures/ low temperatures, you'd want to switch your equation of state (EOS) from ideal gas law to something else. Peng-Robinson would be a good choice for a non-polar gas like Nitrogen, if its >10-50 atm pressure and/or < -50C temperature.

At 20 degC, 1.00atm to 3kPa gauge pressure, ideal gas law predicts nitrogen would increase in density by 2.9608%. Whereas Peng-Robinson predicts it would increase in density by ever-so-slightly more, 2.9623%. This is truly negligible, so better to use the simples EOS for explainability (which would be the ideal gas law).

Yeah, I didn’t know enough to quantify those effects! :-)

No.

> balloon use ... helium became much, much more expensive

More than just from inflation? (sorry, not sorry!)

Nitrogen? That's basically just air, what good would a balloon be using nitrogen? Might as well just blow it up with your lungs. It's certainly not going to float in any case.

I think you're correct it's just air being mixed in not nitrogen, specifically. Stores like Party City started pushing things like arches and stems and other things that hold up balloons up rather than float. It is a lot cheaper to sell a larger quantity of balloons filled with air than a few helium-filled balloons. They also switched their floating gas mix to 60/40 to reduce costs (except for mylar balloons which are heavier and require 100 to float). That's how I remember it from buying balloons for birthday parties a few years ago.