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An Eggy Experiment

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Tetenterre
Posts: 3244
Joined: March 13th, 2011, 11:36 am

An Eggy Experiment

#1 Post by Tetenterre » August 7th, 2015, 12:45 pm

Caveat: Sample size = 6

Preamble: Some old friends were in the area a couple of weeks ago and dropped in to visit. They were house-sitting for someone else who keeps ducks, and brought us a dozen duck eggs of unknown vintage.

This morning, there were half a dozen left, so I decided they should become egg sarnies, salad Nicoise, etc. Being slightly concerned that some may be "off", I did the traditional "float" test. Two floated. I hard-boiled the other four; no indication that the "sinkers" were off. I decided to see how badly "off" the floaters were, so I took them outside and cracked them into separate bowls. No unpleasant smell and no indication they were off. They made a rather nice omelette.

Conclusion: Whilst it may be true that rotten eggs float, it is not the case that if an egg floats it is necessarily rotten.
Steve

Quantum Theory: The branch of science with which people who know absolutely sod all about quantum theory can explain anything.

thundril
Posts: 3607
Joined: July 4th, 2008, 5:02 pm

Re: An Eggy Experiment

#2 Post by thundril » August 7th, 2015, 2:06 pm

Interesting Tet.
I've never quite understood how the condition of the contents changes the buoyancy of the egg.
For the buoyancy to change, either the total mass must decrease, or the volume of the shell must increase.
If the internal fluids merely undergo a phase change from liquid to gas, that wouldn't change the mass.
So is it that some of the internal fluids leak out through the shell when they turn to gas? Or is it that the gas pressure forces the shell to expand sufficiently to increase the volume without changing the mass?

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Tetenterre
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Re: An Eggy Experiment

#3 Post by Tetenterre » August 7th, 2015, 3:02 pm

Eggshells are permeable to gases; as the egg decays, some of the contents turn to gas, some of which escapes through the shell, reducing the mass, and hence the density, of the egg.

This sort of explanation, which infests the internet, is obviously incorrect:
The reason this method works is because the eggshells are porous, which means they allow some air to get through. Fresh eggs have less air in them, so they sink to the bottom. But older eggs have had more time for the air to penetrate the shells, so they're more buoyant and will float.
Steve

Quantum Theory: The branch of science with which people who know absolutely sod all about quantum theory can explain anything.

thundril
Posts: 3607
Joined: July 4th, 2008, 5:02 pm

Re: An Eggy Experiment

#4 Post by thundril » August 7th, 2015, 11:27 pm

thanhks, Tet. Yes, the idea that 'air' somehow has negative mass is widespread. Teach more basic science and less religion!

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Alan C.
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Re: An Eggy Experiment

#5 Post by Alan C. » August 9th, 2015, 5:50 pm

The float/sink thing works with seeds, floaters won't germinate.
Abstinence Makes the Church Grow Fondlers.

thundril
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Joined: July 4th, 2008, 5:02 pm

Re: An Eggy Experiment

#6 Post by thundril » August 10th, 2015, 1:14 pm

Alan C. wrote:The float/sink thing works with seeds, floaters won't germinate.
Coo! Any idea why? Too much water has evaporated away, or something more complex?

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