a bottle of water thrown overboard...
Discussion
My father-in-law and i were having a conversation yesterday regarding relative buoyancy.
The experiment is "you fill a plastic bottle to the brim with fresh water, seal it and throw it into the ocean" what would happen???
it threw up a number of questions (neither of us is in any way scientific, so please go easy on me)
that it sinks has been observed ;-) this is presumably due to salt water having more buoyancy than fresh water and plastic.
how fast would it sink?
is there a depth that it would reach and then stay put? or would it just keep going until it hit the bottom regardless
what depth would it need to reach in order to never rot or degrade (no sunlight)?
would it ever pop due to depth?
other than the questions above, does anyone have any other observations i hadn't thought of?
The experiment is "you fill a plastic bottle to the brim with fresh water, seal it and throw it into the ocean" what would happen???
it threw up a number of questions (neither of us is in any way scientific, so please go easy on me)
that it sinks has been observed ;-) this is presumably due to salt water having more buoyancy than fresh water and plastic.
how fast would it sink?
is there a depth that it would reach and then stay put? or would it just keep going until it hit the bottom regardless
what depth would it need to reach in order to never rot or degrade (no sunlight)?
would it ever pop due to depth?
other than the questions above, does anyone have any other observations i hadn't thought of?
Greg_D said:
My father-in-law and i were having a conversation yesterday regarding relative buoyancy.
The experiment is "you fill a plastic bottle to the brim with fresh water, seal it and throw it into the ocean" what would happen???
is there a depth that it would reach and then stay put? or would it just keep going until it hit the bottom regardless
All the way to the bottom.The experiment is "you fill a plastic bottle to the brim with fresh water, seal it and throw it into the ocean" what would happen???
is there a depth that it would reach and then stay put? or would it just keep going until it hit the bottom regardless
It will only sink if its density is greater than sea water. The salt in sea water increases the water's density so things float more readily.
I would expect the bottle to float just on the surface but if it has been observed to sink then this will be due to the density of the plastic bottle itself, or the temperature difference between the waters.
As to the rate of fall and whether it continues to sink depends on the temperature profile of the sea. The bottle will sink as long as its density is higher, but the rate will change depending on the sea water's density. Stokes Law predicts the rate of sinking for spherical objects (bottles).
Mike...
I would expect the bottle to float just on the surface but if it has been observed to sink then this will be due to the density of the plastic bottle itself, or the temperature difference between the waters.
As to the rate of fall and whether it continues to sink depends on the temperature profile of the sea. The bottle will sink as long as its density is higher, but the rate will change depending on the sea water's density. Stokes Law predicts the rate of sinking for spherical objects (bottles).
Mike...
This is a very interesting experiment.
My theory is that it will float. The salt water being denser than the fresh water inside, also i recon the plastic will give buoyancy and keep it afloat.
If i wanted to test this at home, whats the best way to replicate salt water? literally chuck some salt in some water and swish it around?
My theory is that it will float. The salt water being denser than the fresh water inside, also i recon the plastic will give buoyancy and keep it afloat.
If i wanted to test this at home, whats the best way to replicate salt water? literally chuck some salt in some water and swish it around?
...will float.
At least a bottle of fresh water thrown into sea water will float. In fact it is a pretty standard abandon ship drill to throw any bottles of drinking water over the side (assuming you don't have time to stow them properly) so you can collect them once in your raft/boat.
1 litre fresh water weighs 1kg, 1 litre sea water weighs 1.025kg. Most disposable plastic bottles weigh less than 25g so the total is less dense than the sea water it displaces.
At least a bottle of fresh water thrown into sea water will float. In fact it is a pretty standard abandon ship drill to throw any bottles of drinking water over the side (assuming you don't have time to stow them properly) so you can collect them once in your raft/boat.
1 litre fresh water weighs 1kg, 1 litre sea water weighs 1.025kg. Most disposable plastic bottles weigh less than 25g so the total is less dense than the sea water it displaces.
LimaDelta said:
...will float.
At least a bottle of fresh water thrown into sea water will float. In fact it is a pretty standard abandon ship drill to throw any bottles of drinking water over the side (assuming you don't have time to stow them properly) so you can collect them once in your raft/boat.
1 litre fresh water weighs 1kg, 1 litre sea water weighs 1.025kg. Most disposable plastic bottles weigh less than 25g so the total is less dense than the sea water it displaces.
perfect answer, thanks very much, i love this place sometimes..At least a bottle of fresh water thrown into sea water will float. In fact it is a pretty standard abandon ship drill to throw any bottles of drinking water over the side (assuming you don't have time to stow them properly) so you can collect them once in your raft/boat.
1 litre fresh water weighs 1kg, 1 litre sea water weighs 1.025kg. Most disposable plastic bottles weigh less than 25g so the total is less dense than the sea water it displaces.
I shall enjoy telling him he is full of s**t...
ps, it was him who said that he had seen it sink, he had obviously seen it go under, it probably reappeared a minute or 2 later.
A bottle of water you buy usually has a small air gap as well, which will help it float. If it's completely full it'll have a better chance of sinking, but as said that depends on the density of the plastic.
Salinity increases with depth (makes sense as the saltier it is the heavier it is) so potentially there will be a point where the density of the seawater matches the density of the water bottle and it will stop sinking. It will never get crushed as the water in the bottle isn't compressible assuming there's no air gap. If there is an air gap that will get compressed and the density of the bottle will increase.
Salinity increases with depth (makes sense as the saltier it is the heavier it is) so potentially there will be a point where the density of the seawater matches the density of the water bottle and it will stop sinking. It will never get crushed as the water in the bottle isn't compressible assuming there's no air gap. If there is an air gap that will get compressed and the density of the bottle will increase.
RizzoTheRat said:
Salinity increases with depth (makes sense as the saltier it is the heavier it is) so potentially there will be a point where the density of the seawater matches the density of the water bottle and it will stop sinking.
i agree with the logic, but this diagram from wiki seems to contradict what you are sayinghttps://en.wikipedia.org/wiki/Seawater#/media/File...
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