Of course the difference is quite miniscule but I became curious while standing on my scale exhaling to look leaner than I was. Unfortunately my scale isn’t precise enough to be able to test this so here I am. Any explanation would be greatly appreciated 🙂
In: Physics
Exhale into a large empty graduated cylinder that has a piston in the interior (like blowing into an empty syringe to fill it with air.) They make things like this for measuring lung capacity. Measure.your lung capacity. Then multiply your lung capacity by the mass of air at your altitude and temperature. That will tell you exactly how much mass you gain by inhaling.
It shouldn’t matter assuming your air ways are open. The reason is that the air inside your lungs would displace their own weight of air outside your body giving a buoyant force to perfectly cancel our the added mass. That said if you close your air ways and pressurize your lungs you will gain weight as the air will not displace as much and you won’t have as much botany force as before.
You will gain mass by inhaling, but the reading on the scale won’t show any difference. That’s because the scale never actually measures your weight. It measures your weight plus the weight of the air above the scale. It’s just calibrated to show zero if there is nothing but air on top of it. (I.e. you are not standing on it).
Now when you stand on it, you are replacing some of the air with your body (which is heavier than air).
When you inhale, you are replacing some more of the ambient air, but this time only with air (which weighs the same).
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