I’d say that the density of the raspberry is so close to water that small changes in the pressure and their effect of the air bubbles trapped in the raspberry make it sink or float.
So for example: the density of water is 1g/ml and the density of the raspberry is 1.05 g/ml. When the air pressure drops, the bubbles on the raspberry enlarge and make the raspberry more buoyant. Or in other words, the effective density becomes less than 1g/ml and therefore it floats.
The raspberry that’s always floating may have lower density or more bubbles on it and therefore change in pressure doesn’t affect it.
Is this the same reason that a raisin ( or mistranslation for grape) is supposed to continue rising and falling in champagne? I’ve never had the funding to do that experiment!
It is. The raisin has a high surface area to collect bubbles, and they pull it to the surface. Once surfaced, the bubbles are released into the air and no longer support the raisin, so it sinks.
Try it with sparkling water or another fizzy drink.
Nice experiment! It reminds me of something:
If you put a dried slice of pineapple in a glass of water it will sink first, but will come up to the top in a couple of minutes.
I’d say that the density of the raspberry is so close to water that small changes in the pressure and their effect of the air bubbles trapped in the raspberry make it sink or float.
So for example: the density of water is 1g/ml and the density of the raspberry is 1.05 g/ml. When the air pressure drops, the bubbles on the raspberry enlarge and make the raspberry more buoyant. Or in other words, the effective density becomes less than 1g/ml and therefore it floats. The raspberry that’s always floating may have lower density or more bubbles on it and therefore change in pressure doesn’t affect it.
Is this the same reason that a raisin ( or mistranslation for grape) is supposed to continue rising and falling in champagne? I’ve never had the funding to do that experiment!
It is. The raisin has a high surface area to collect bubbles, and they pull it to the surface. Once surfaced, the bubbles are released into the air and no longer support the raisin, so it sinks.
Try it with sparkling water or another fizzy drink.
Nice experiment! It reminds me of something:
If you put a dried slice of pineapple in a glass of water it will sink first, but will come up to the top in a couple of minutes.