How does this happen?

[ryan]

I was boiling water in a pot and just about to put in the linguine when I decided to cook some sausage too. I just turned off the stove so that the noodles and the sausage would start at the same time as I prepared the sausage.

I turned back on the burner to start boiling the water again and threw the sausage in the pan. I still have not put the pasta in because I like to wait until the water is boiling.

Stay with me, it gets interesting.

So I am cooking the sausage and I keep looking at the pot of water, but there is no sign of boiling. I thought that was weird since I had water boiling just 5 minutes ago.

A few more minutes go by, and now it's starting to get frustrating because the sausage is almost done. I can see that the element under the pot is red hot, so the stove was working fine.

Then I walk over to the fridge and I jump as I hear an explosion coming from the stove behind me. I turn around and the water is bursting out of the pot. It shot so high It that it got the overhead fan wet.

It was quite scary, and probably would have melted my face off if I were standing over the pot.

The water somehow hit an extremely high state of instability without releasing its energy. There was nothing but water and whatever extras are put in at the treatment plant, but it's generaly good drinkable water.

What happened and how?

 

[ryan]

This also happened once when I boiled water in a mug. I boiled water in the microwave, but I was late getting to it to put in a tea bag, so I just hit another minute without disturbing the mug. The water hadn't boiled again, but I thought it was close enough and took it out. I disturbed the mug when I grabbed it, and it did made a similar but much smaller scale explosion.

 

[beero1000]

 Superheating

 

[ryan]

 Superheating

Hey thanks, I am surprised that H-bonding can be so strong collectively. But it couldn't have formed a lattice since the water was clearly still moving a little.

 

[bilby]

Superheating is common with new pans; in order to boil, the steam bubbles need nucleation sites, and a highly polished new pan filled with clean water doesn't provide any.

The trick is to add something that allows nucleation - you can add salt just before the water reaches boiling point, and that will work. The salt allows the dissolved air to nucleate (as it will be supersaturated in hot water) and then the air bubbles will work as nucleation sites for the steam; But if you add the salt too early, it dissolves, and the opportunity is missed. Salt added to cold water can also cause pitting of Stainless Steel pans.

A more certain method is to break up a strand of pasta, and add that to the pan - the rough surface of dried pasta will do the job, and one over cooked strand of spaghetti or linguini won't be noticed in the finished dish. Again it's best to add this after at least some of the heating has been done.

Superheated water can be a serious hazard in a kitchen, and can lead to severe burns. Another option (if you care more for safety than for appearances) is to use a scouring pad to scratch the bottom of your pan. Old pans generally have enough scratches to prevent superheating (even if the scratches are too small to be obvious to a visual inspection).

In lab glassware, a few 'bumping granules' - bits of ground up broken glass - are added to help liquids boil in clean, smooth containers; but obviously you don't want them in your dinner.

 

[Malintent]

It is odd for that to happen without using some extremely pure water... like distilled. your water superheated without entering the boiling state because there were very little minerals in the water, and the container was perfectly smooth.. like glass.

When heating up a mug of water in the microwave, there are warnings in the manual to be careful removing the item, as a sudden boil may erupt as soon as it is jiggled a bit.

Super cooling works similarly.. you can get water down below freezing without it actually changing state. Then, you can pour the water gently out of its container and it will pour normally.. until it hits a surface when it instantly transforms into a solid.

edited to add: You really should be putting a good amount of kosher or sea salt (not table salt - ever - for anything) in your water for pasta... it's the only way to season the inside of a noodle... more important for thicker pastas.

 

[beero1000]

It is odd for that to happen without using some extremely pure water... like distilled. your water superheated without entering the boiling state because there were very little minerals in the water, and the container was perfectly smooth.. like glass.

When heating up a mug of water in the microwave, there are warnings in the manual to be careful removing the item, as a sudden boil may erupt as soon as it is jiggled a bit.

Super cooling works similarly.. you can get water down below freezing without it actually changing state. Then, you can pour the water gently out of its container and it will pour normally.. until it hits a surface when it instantly transforms into a solid.

edited to add: You really should be putting a good amount of kosher or sea salt (not table salt - ever - for anything) in your water for pasta... it's the only way to season the inside of a noodle... more important for thicker pastas.

From the wiki page:

There is a common belief that superheating can occur only in pure substances. This is untrue, as superheating has been observed in coffee and other impure liquids. Impurities do prevent superheating if they introduce nucleation sites (rough areas where gas is trapped); for example, sand tends to suppress superheating in water. Dissolved gas can also provide nucleation sites when it comes out of solution and forms bubbles. However, an impurity such as salt or sugar, dissolved in water to form a homogeneous solution, does not prevent superheating. Other liquids are known to superheat including 2% milk and almond milk.

and from another source (emphasis mine):

Of course, impure water can "explode." That's why people get scalded; they re-heat their coffee in microwave ovens and then quickly add sugar. Coffee is extremely impure water! To cause "coffee explosions," you don't need special pure water. All you need is water that lacks micro-bubbles.

It seems that some recent TV show tries to prove that only pure water can superheat and "explode." This is wrong. Probably the creators of that show did not know an important fact: nucleation centers for boiling are actually tiny bubbles. While solid crystals will grow upon solid nucleation centers found in impure liquids, the gas bubbles in cola, and in boiling pots, grow upon microscopic seed-bubbles. You can't grow crystals unless you have a solid microscopic seed. And you can't boil water unless you have invisibly small seed-bubbles present. It doesn't matter how filthy your water is, or how many crystal nucleation centers it contains... if it lacks seed-bubbles then it will not boil normally, instead it will superheat.

Clearly this has nothing to do with distilled water. In fact it's very easy to boil ultra-pure distilled water normally, without explosions. First chill and shake up your bottle of distilled water thoroughly. This creates lots of nucleation centers for boiling. And it's easy to make "impure" water explode; impure water called coffee and soup. If tap water has had all the bubbles cleared out by earlier boiling or by simply sitting for days in an open container, then it will superheat, and when sugar is dumped in, it will go DOOSH and spray all over.

 

[Loren Pechtel]

This is the first time I've heard of it happening in a pot. It's more common in the microwave with the much more evenly applied heat.

 

[Kharakov]

At the opposite end of the temp spectrum:

You can do a neat trick with Gatorade / Powerade type drinks: put them in the freezer until they are about 27 f (-3 c) *. If you do not disturb them when you remove them from the freezer, you can pour them into a glass in liquid form, when they hit the bottom of the glass they form into a slushy that piles up. If you shake or jostle the Gatorade, it will turn into a slushy inside the bottle, so be careful if you want to see the liquid turning into a slushy.

* I am not sure of the exact temp, and do not have access to an accurate thermometer. If you get it too cold, it forms a solid.


It's good on a hot summer day.

 

[ryan]

Does anyone have any ideas on how this happens. I can't seem to find any good information on what exactly is happening molecularly.

Does the water still change to the gas state? I don't remember seeing any steam when I was waiting for the water to boil.

 

[Juma]

Does anyone have any ideas on how this happens. I can't seem to find any good information on what exactly is happening molecularly.

Does the water still change to the gas state? I don't remember seeing any steam when I was waiting for the water to boil.

not until it "exploded".

 

[Kharakov]

Does anyone have any ideas on how this happens. I can't seem to find any good information on what exactly is happening molecularly.

Bilby already said it. The answer was: steam bubbles need some sort of surface to nucleate (form!) upon (even if it's just another bubble).

If you have a clean SMOOTH surfaced pot
your water is relatively free of dust and doesn't have a bunch of ions (salt) in it (mehh. not positive about ions... anyone?)
you don't jostle the pot
the water in the pot does not have a huge amount of convection because it is pretty uniformly hot
the metal is not expanding and making microvibrations because it is uniformly hot, etc......

You might heat your water up an extra bit, which will allow it to do what you described.

Does the water still change to the gas state?

Yes. I doubt it's a plasma.

 

[ryan]

Does anyone have any ideas on how this happens. I can't seem to find any good information on what exactly is happening molecularly.

Does the water still change to the gas state? I don't remember seeing any steam when I was waiting for the water to boil.

not until it "exploded".

That's the answer I was afraid of because now I have even more questions.

What force is holding the molecules back from vaporizing that isn't there when water vaporizes at 100 C? Hydrogen bonding is the main attraction force that gives water its properties. No strong lattice structure forms to give it more strength because the molecules were definitely not still like with ice.

What is it about this nucleation that causes vapor.

 

[ryan]

Bilby already said it. The answer was: steam bubbles need some sort of surface to nucleate (form!) upon (even if it's just another bubble).

If you have a clean SMOOTH surfaced pot
your water is relatively free of dust and doesn't have a bunch of ions (salt) in it (mehh. not positive about ions... anyone?)
you don't jostle the pot
the water in the pot does not have a huge amount of convection because it is pretty uniformly hot
the metal is not expanding and making microvibrations because it is uniformly hot, etc......

You might heat your water up an extra bit, which will allow it to do what you described.

Does the water still change to the gas state?

Yes. I doubt it's a plasma.

I was always taught that water will change phase at 100 C under 101.325 kPa. I didn't know that there was this other extremely important variable that I have yet to understand. It's like finding an area with no gravity and people saying that it is simply because of the type of soil on the ground - what?

In other words I'm rattled kharakov, and I don't know what to believe anymore.

 

[bilby]

not until it "exploded".

That's the answer I was afraid of because now I have even more questions.

What force is holding the molecules back from vaporizing that isn't there when water vaporizes at 100 C? Hydrogen bonding is the main attraction force that gives water its properties. No strong lattice structure forms to give it more strength because the molecules were definitely not still like with ice.

What is it about this nucleation that causes vapor.

In order for a bubble to grow, you need to start with a smaller bubble.

If no bubbles are present, then how would any particular part of the water be the part that first forms a cavity? Why would the first steam bubble form here, and not there?

The force that holds the superheated water together is the same intermolecular force that produces surface tension. A bubble is a new surface.

A structure with no weakest point can only fail when it is subjected to sufficient stress to cause failure everywhere at once; and then it must fail spectacularly, everywhere at once.

Add a few 'weak spots' and the structure will fail at those points and relieve the stress, before it has built up to a sufficient level to cause a catastrophic failure.

I can thoroughly recommend the work of the excellent J E Gordon, whose masterwork "The New Science of Strong Materials (or Why You Don't Fall Through the Floor)", first published in 1968, and still in print, provides a superb starting point for understanding how materials fail under load (and why they often don't). The book doesn't discuss superheating, but when you consider that water is a structure of molecules held together by a network of hydrogen bonds, you will see how this is directly relevant to the phenomenon we are discussing.

https://www.amazon.com/Science-Materials-through-Princeton-Library/dp/0691125481

You should also read his companion work, "Structures (or Why Things Don't Fall Down)".

 

[beero1000]

Bilby already said it. The answer was: steam bubbles need some sort of surface to nucleate (form!) upon (even if it's just another bubble).

If you have a clean SMOOTH surfaced pot
your water is relatively free of dust and doesn't have a bunch of ions (salt) in it (mehh. not positive about ions... anyone?)
you don't jostle the pot
the water in the pot does not have a huge amount of convection because it is pretty uniformly hot
the metal is not expanding and making microvibrations because it is uniformly hot, etc......

You might heat your water up an extra bit, which will allow it to do what you described.




Yes. I doubt it's a plasma.

I was always taught that water will change phase at 100 C under 101.325 kPa. I didn't know that there was this other extremely important variable that I have yet to understand. It's like finding an area with no gravity and people saying that it is simply because of the type of soil on the ground - what?

In other words I'm rattled kharakov, and I don't know what to believe anymore.

I think it's safe to say that the universe is a complicated place and that exceptions exist for almost every rule.

Here is a good article: When water does not boil at the boiling point

 

[ryan]

That's the answer I was afraid of because now I have even more questions.

What force is holding the molecules back from vaporizing that isn't there when water vaporizes at 100 C? Hydrogen bonding is the main attraction force that gives water its properties. No strong lattice structure forms to give it more strength because the molecules were definitely not still like with ice.

What is it about this nucleation that causes vapor.

In order for a bubble to grow, you need to start with a smaller bubble.

If no bubbles are present, then how would any particular part of the water be the part that first forms a cavity? Why would the first steam bubble form here, and not there?

The force that holds the superheated water together is the same intermolecular force that produces surface tension. A bubble is a new surface.

A structure with no weakest point can only fail when it is subjected to sufficient stress to cause failure everywhere at once; and then it must fail spectacularly, everywhere at once.

Add a few 'weak spots' and the structure will fail at those points and relieve the stress, before it has built up to a sufficient level to cause a catastrophic failure.

I can thoroughly recommend the work of the excellent J E Gordon, whose masterwork "The New Science of Strong Materials (or Why You Don't Fall Through the Floor)", first published in 1968, and still in print, provides a superb starting point for understanding how materials fail under load (and why they often don't). The book doesn't discuss superheating, but when you consider that water is a structure of molecules held together by a network of hydrogen bonds, you will see how this is directly relevant to the phenomenon we are discussing.

https://www.amazon.com/Science-Materials-through-Princeton-Library/dp/0691125481

You should also read his companion work, "Structures (or Why Things Don't Fall Down)".

Yeah, the intermolecular forces that matter here are the hydrogen bonds. Each hydrogen bond will be at some average amount of bonding energy. They constantly break and reattach to other water molecules.

So don't you think it's strange that we give water a boiling point based on the accessibility of nucleation sites? It would just seem more precise to base water boiling/evaporation on the maximum amount of heat energy that a mol of water (take an average of each h-bond and multiply it by 1 mol) can absorb before "exploding" into pure vapor. It will have to give at some point no matter how perfect the conditions are, a maximum liquid water enthalpy boundary. I am calling it ryan's boundary.

And they must know about this. In first year chemistry and organic chemistry we learn so much about the molecular properties that account for the much more general observations. I can't even begin to imagine that they haven't thought about this.

 

[Elixir]

In order for a bubble to grow, you need to start with a smaller bubble.

If no bubbles are present, then how would any particular part of the water be the part that first forms a cavity? Why would the first steam bubble form here, and not there?

The force that holds the superheated water together is the same intermolecular force that produces surface tension. A bubble is a new surface.

A structure with no weakest point can only fail when it is subjected to sufficient stress to cause failure everywhere at once; and then it must fail spectacularly, everywhere at once.

Add a few 'weak spots' and the structure will fail at those points and relieve the stress, before it has built up to a sufficient level to cause a catastrophic failure.

I can thoroughly recommend the work of the excellent J E Gordon, whose masterwork "The New Science of Strong Materials (or Why You Don't Fall Through the Floor)", first published in 1968, and still in print, provides a superb starting point for understanding how materials fail under load (and why they often don't). The book doesn't discuss superheating, but when you consider that water is a structure of molecules held together by a network of hydrogen bonds, you will see how this is directly relevant to the phenomenon we are discussing.

https://www.amazon.com/Science-Materials-through-Princeton-Library/dp/0691125481

You should also read his companion work, "Structures (or Why Things Don't Fall Down)".

Yeah, the intermolecular forces that matter here are the hydrogen bonds. Each hydrogen bond will be at some average amount of bonding energy. They constantly break and reattach to other water molecules.

So don't you think it's strange that we give water a boiling point based on the accessibility of nucleation sites? It would just seem more precise to base water boiling on the maximum amount of heat energy that a mol of water (take an average of each h-bond and multiply it by 1 mol) can absorb before "exploding" into pure vapor.

And they must know about this. In first year chemistry and organic chemistry we learn so much about the molecular properties that account for the much more general observations. I can't even begin to imagine that they haven't thought about this.

I dunno... I was taught about superheated water waaaaay back when. Never experienced it until microwaves came around. Pretty easy to replicate if you have a very clean, smooth glass and some relatively pure (not tap) water. First time, it got me pretty good, but I immediately recognized what had occurred. Since then I'm literally once burned, twice shy of liquids that have been microwaved. They like to blow up when disturbed - hydrogen bonds be damned!

 

[bilby]

In order for a bubble to grow, you need to start with a smaller bubble.

If no bubbles are present, then how would any particular part of the water be the part that first forms a cavity? Why would the first steam bubble form here, and not there?

The force that holds the superheated water together is the same intermolecular force that produces surface tension. A bubble is a new surface.

A structure with no weakest point can only fail when it is subjected to sufficient stress to cause failure everywhere at once; and then it must fail spectacularly, everywhere at once.

Add a few 'weak spots' and the structure will fail at those points and relieve the stress, before it has built up to a sufficient level to cause a catastrophic failure.

I can thoroughly recommend the work of the excellent J E Gordon, whose masterwork "The New Science of Strong Materials (or Why You Don't Fall Through the Floor)", first published in 1968, and still in print, provides a superb starting point for understanding how materials fail under load (and why they often don't). The book doesn't discuss superheating, but when you consider that water is a structure of molecules held together by a network of hydrogen bonds, you will see how this is directly relevant to the phenomenon we are discussing.

https://www.amazon.com/Science-Materials-through-Princeton-Library/dp/0691125481

You should also read his companion work, "Structures (or Why Things Don't Fall Down)".

Yeah, the intermolecular forces that matter here are the hydrogen bonds. Each hydrogen bond will be at some average amount of bonding energy. They constantly break and reattach to other water molecules.

So don't you think it's strange that we give water a boiling point based on the accessibility of nucleation sites? It would just seem more precise to base water boiling/evaporation on the maximum amount of heat energy that a mol of water (take an average of each h-bond and multiply it by 1 mol) can absorb before "exploding" into pure vapor. It will have to give at some point no matter how perfect the conditions are, a maximum liquid water energy boundary. I am calling it ryan's boundary.

And they must know about this. In first year chemistry and organic chemistry we learn so much about the molecular properties that account for the much more general observations. I can't even begin to imagine that they haven't thought about this.

They have - and did almost from the outset of modern science.

Check out the article beero1000 linked to above - it's only a few pages, but it covers the history as well as the science, and is both informative and interesting.

 

[ryan]

https://www.amazon.com/Science-Materials-through-Princeton-Library/dp/0691125481

You should also read his companion work, "Structures (or Why Things Don't Fall Down)".

This reminds me that there was a breakthrough a few years ago understanding what a breaking point is. Maybe I am in way over my head here.

- - - Updated - - -

Yeah, the intermolecular forces that matter here are the hydrogen bonds. Each hydrogen bond will be at some average amount of bonding energy. They constantly break and reattach to other water molecules.

So don't you think it's strange that we give water a boiling point based on the accessibility of nucleation sites? It would just seem more precise to base water boiling/evaporation on the maximum amount of heat energy that a mol of water (take an average of each h-bond and multiply it by 1 mol) can absorb before "exploding" into pure vapor. It will have to give at some point no matter how perfect the conditions are, a maximum liquid water energy boundary. I am calling it ryan's boundary.

And they must know about this. In first year chemistry and organic chemistry we learn so much about the molecular properties that account for the much more general observations. I can't even begin to imagine that they haven't thought about this.

They have - and did almost from the outset of modern science.

Check out the article beero1000 linked to above - it's only a few pages, but it covers the history as well as the science, and is both informative and interesting.

The link doesn't work for me.