AMICI OVER THE OCEAN
 
 
     
Welcome!
Welcome to Amici Over the Ocean forum!

If this is your first visit, be sure to check out our Terms of Service and Advices
PLEASE NOTE: Some areas are not accessible or are hidden to guests.
Please log in or register to enjoy the entire site!
Registration is quick and easy!

CLICK HERE TO REGISTER - CLICK HERE TO LOG IN

Erupted Hot Water Phenomena in Microwave Ovens

 
Post new topic   Reply to topic    AMICI OVER THE OCEAN Forum Index -> Health and Home Safety - Salute e Sicurezza domestica
View previous topic :: View next topic  
Author Message
maria
Addicted to this place
Addicted to this place


Joined: 10 Aug 2006
Posts: 532
Location: Connecticut, USA

PostPosted: Thu Nov 30, 2006 5:56 am    Post subject: Erupted Hot Water Phenomena in Microwave Ovens Reply with quote

from
Only registered users can see links on this forum!
Register or Login on forum!



Erupted Hot Water Phenomena in Microwave Ovens


The FDA received reports in the past of serious skin burns or scalding injuries around people's hands and faces as a result of hot water erupting out of a cup after it had been over-heated in a microwave oven. Over-heating of water in a cup can result in superheated water (water heated past its boiling temperature), which does not appear to be boiling.

This type of phenomena occurs if water is heated in a clean cup. If foreign materials such as instant coffee or sugar are added before heating, the risk is greatly reduced. If superheating has occurred, a slight disturbance or movement such as picking up the cup, or pouring in a spoon full of instant coffee, may result in a violent eruption with the boiling water exploding out of the cup.


------------------------

My two cents here

Water needs 'nucleation sites' for boiling to take place and bubbles to form. These can be dust in the water, impurities or imperfections in wall boundaries, such as small crevices or bumps in cups or metal pots. If water were perfectly pure or the container were smooth then boiling would not occur even if the water were heated above 212 F. A bubble needs something to attach itself to in order to be born. This phenomenon occurs in all liquids, but it is more pronounced in water because of its high surface tension, i.e, water molecules love to stick to each other....

you see the result of surface tension with the naked eye in drops of water.......



Only registered users can see links on this forum!
Register or Login on forum!



...or the surface of water becoming convex in a container right after it becomes completely full and right before it starts to spill....

.....Ripples of water are due to surface tension...


Only registered users can see links on this forum!
Register or Login on forum!




This is how Mother Nature wants it. In the phenomenon described above of hot water erupting when heated in a microwave oven is that water does not appear to be boiling although water is very hot because boiling could not start and bubbles could be formed due to lack of 'nucleation sites' inside and around the water. It does not mean that the water is not sufficiently hot. Actually it could be above the boiling point temperature 100C (212F).

Then what happens is that the person inserts a spoon or puts a bag of tea or whatever into the cup, breaking up the surface tension and instantaneously 'nucleation sites' are introduced and since the water is above boiling temperature, bubbles are started instantaneously and the water erupts. Putting impurities into the water before heating it, like instant coffee or sugar ensures that boiling takes place at the normal boiling temperature.

It may be also a good idea while boiling water for pasta or other stuff on the range, to put the salt in the water at the beginning of the heating process, although since heating on a range is slower there is more time for bubbles to find a nucleation site and form before reaching superheated water temperatures as compared to heating water in a microwave oven.

Maria

_________________
We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.
T. S. Eliot
Back to top
View user's profile Send private message
Carole B
Contributor
Contributor


Joined: 27 Jun 2006
Posts: 1973
Location: Valtellina - Northern Italy

PostPosted: Thu Nov 30, 2006 10:46 am    Post subject: Reply with quote

Geez - thanks for that information Maria....
I do have a microwave, but don't use it a great deal - and not at all for actually 'cooking' something (previous attempts have always ended in disaster d'oh! ).

But I do use it to defrost things sometimes, for heating the milk every morning for my caffe latte - and for heating water on occasion!

So thanks to your warning I will be extra careful now...

Thank you.

_________________



Only registered users can see links on this forum!
Register or Login on forum!

Back to top
View user's profile Send private message
marisa6
Site Regular
Site Regular


Joined: 30 Jun 2006
Posts: 437
Location: Scotland

PostPosted: Thu Nov 30, 2006 2:19 pm    Post subject: Reply with quote

Wow Maria

I'd heard of this problem with water and microwaves - but your explanation of why it happens is fascinating. Thanks for explaining it so clearly. That was an amazing lesson in physics! Absolutely fascinating. This will come up at coffee with the girls tomorrow!!!

Marisa Applause
Back to top
View user's profile Send private message
maria
Addicted to this place
Addicted to this place


Joined: 10 Aug 2006
Posts: 532
Location: Connecticut, USA

PostPosted: Thu Nov 30, 2006 2:19 pm    Post subject: Reply with quote

My parents bought a microwave oven when they lived in St. Louis back in the 70s, so i learned to use it long long ago. In my experience, the only thing that comes Ok cooked in microwave ovens is vegetables, specially the frozen types. Actually I think my mother put it to use more than me. In my opinion meat in general does not taste well when cooked in a micro. Oh, poached fish also comes good in a microwave oven , but its smell stays in there forever, so I avoid it. As I said, i mainly use it for frozen veggies. I also lightly microwave veggies for a couple of minutes when cooking chinese stir fry. My 30 year chinese cookbook recommends that I parboil vegetables like broccoli or peppers for 2 minutes before adding them to the wok. Instead I put them in a glass bowl, add few drops of water and zap it for a couple of minutes.

It is also great for softening butter when baking. Other than that and the uses you cite, I don't use my microwave, but these few things I do greatly speed up my cooking time.

My husband uses it for warming leftover meals. Since nowdays I am busy with studying, we have leftovers more often than I rather admit. I do not like the way microwave alters the taste of meat unless it is heated very lightly, specially roasted or fried meat. It does not bother my husband. I rather eat it cold.

Sorry for the rambling this morning.

Maria

_________________
We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.
T. S. Eliot
Back to top
View user's profile Send private message
marisa6
Site Regular
Site Regular


Joined: 30 Jun 2006
Posts: 437
Location: Scotland

PostPosted: Thu Nov 30, 2006 2:35 pm    Post subject: Reply with quote

I love science. The problem is that I'm really not any good at it! I love it when someone gives a clear and concise explanation of why something that makes me curious happens.

We have a TV program over here called 'Brainiac - Science Abuse', which would probably do an experiment with the boiling water described above. My brother-in-law got the kids into watching it. He is a bit of a brainiac too. My sister and brother-in-law both have PhDs in engineering. His is in nanotechnology, and hers in renewable energy sources. A few years back my younger son came thoughtfully out of the bathroom one morning and asked why little poos splash more than big poos Brick wall I just cast my eyes heavenwards and told him to email his Uncle Chris. About half-an-hour later back came this very detailed explanation about height of the drop, weight and density of the poo, surface tension of the water and gravity etc. Who says scientists don't have a sense of humour....

Marisa xx
Back to top
View user's profile Send private message
maria
Addicted to this place
Addicted to this place


Joined: 10 Aug 2006
Posts: 532
Location: Connecticut, USA

PostPosted: Thu Nov 30, 2006 2:43 pm    Post subject: Reply with quote

marisa6 wrote:
Wow Maria

I'd heard of this problem with water and microwaves - but your explanation of why it happens is fascinating. Thanks for explaining it so clearly. That was an amazing lesson in physics! Absolutely fascinating. This will come up at coffee with the girls tomorrow!!!

Marisa Applause


Thanks Marisa. I think i have observed the behavior of water as long as I remember. Actually it is one of those epiphanies that happens to many during their life, at least the lucky ones like me. They enjoy something as children and then they go to school, go to work and then one day, during a moment of relaxation and day dream, perhaps while watching rain form rivulets on the window panes they realize that they have been in love all along with whatever it is. For me it was watching brooks outdoors or dripping faucets and boiling pots indoors and never been bored by it.

Another thing that happened to me was one day a friend who is very much into astrology asking me my astrological sign and I answer that I am pisces... a sign of water... and then she answers... but I sense fire in you....and then she asks for the exact date and hour and does an astrological chart (it is a snap nowdays with computer) to come up that I am double pisces (now the languange of astrology is foreign to me), in that both my sun and my moon is in pisces, but I have strong mars influence, and mars gives me fire influence... and then I muse amused about this... and then I smack my forehead laughing.... what is my field of expertize at work? Thermo-hydraulics... the study of heat and water! Funny indeed.

Our life and why we do certain things and pursue certain interests is the greatest mystery of all. I just love it!

Maria

_________________
We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.
T. S. Eliot
Back to top
View user's profile Send private message
maria
Addicted to this place
Addicted to this place


Joined: 10 Aug 2006
Posts: 532
Location: Connecticut, USA

PostPosted: Thu Nov 30, 2006 3:01 pm    Post subject: Reply with quote

Quote:
Who says scientists don't have a sense of humour....


Once during a family gathering, my mother or my sister asked to check if it was time to drop the pasta in the pot and my husband who who was standing closest to the range and who is in exactly in the same field as me (from college classes to same department in same company from 1984 to 2005) with a gleam in his eyes called out: "It is in nucleate boiling!" Every one laughed.

...nucleate boiling is when you start seeing the bubbles forming in the bottom of the pot but they haven't started rising to the surface or break out, ... pool boiling... it is when they rise to the surface and vapor excapes to the atmosphere.... it is what cookbooks describe as 'water coming to full boil." Of course, you never drop pasta in the pot at nucleate boiling, but wait until pool boiling...

Maria


-----------------------------------------------------------------------------

Nucleate boiling


Only registered users can see links on this forum!
Register or Login on forum!


_________________
We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.
T. S. Eliot
Back to top
View user's profile Send private message
nuccia
Beautiful Moderator
Beautiful Moderator


Joined: 28 Jun 2006
Posts: 1743
Location: Canada

PostPosted: Fri Dec 01, 2006 12:19 am    Post subject: Reply with quote

I'm confused..and fascinated! all the daily things I have observed with water, you have explained but my favourite explanation is about the poo. What an awesome question and good for you Marisa to actually take the question seriously as he meant it and encourage him to get the answer! I think that is
so important to stimulate children..they are like sponges.

As for microwaves..they're great for Pogos (frozen corn dogs the kids like) or beef patties. I prefer to boil my water in a kettle and whenever I have put it in the microwave I have always added my coffee first...now I'm glad. I did have a little incident with nuking espresso coffee once...what a mess. But I think I just over boiled it.

_________________
---nuccia

Only registered users can see links on this forum!
Register or Login on forum!



Only registered users can see links on this forum!
Register or Login on forum!

Back to top
View user's profile Send private message
marisa6
Site Regular
Site Regular


Joined: 30 Jun 2006
Posts: 437
Location: Scotland

PostPosted: Wed Dec 06, 2006 12:35 am    Post subject: Reply with quote

Ok - along the same lines - but slightly different! Maria, perhaps you could explain why it is that when I open a bottle of soda water it fizzes all over me like a tidal wave, yet when my smug husband opens it it stays in the bottle! What am I doing wrong and why does it happen?

Marisa Eh? Think d'oh!
Back to top
View user's profile Send private message
nuccia
Beautiful Moderator
Beautiful Moderator


Joined: 28 Jun 2006
Posts: 1743
Location: Canada

PostPosted: Sun Dec 17, 2006 5:19 am    Post subject: Reply with quote

Marisa...

I'll tell you what you're doing wrong. You're not shaking the bottle (all the bottles) before he gets to them. I guarantee that will wipe the smile of his face. Very Happy

_________________
---nuccia

Only registered users can see links on this forum!
Register or Login on forum!



Only registered users can see links on this forum!
Register or Login on forum!

Back to top
View user's profile Send private message
maria
Addicted to this place
Addicted to this place


Joined: 10 Aug 2006
Posts: 532
Location: Connecticut, USA

PostPosted: Sun Dec 17, 2006 4:50 pm    Post subject: Reply with quote

Sorry Marisa, but somehow I did not see your post till now when I was flagged that Nuccia had replied to it.

Nuccia is right. You must shake the bottle more than your husband and force carbon dioxide (CO2) to be released out of solution. Then when you open the bottle the bubbles all come out into a tidal wave as you write.

Yes, go ahead and shake his bottle so he gets to experience the same thing, but if you do it too much in advance it will not work. In nature everything wants to be in equilibrium and the gas will again go back into solution with the liquid as before if it sits a while since it trapped inside the bottle and has nowhere else to go.

Pressure and temperature dictates how much gas stays in solution and how much stays out. At the pressure inside the bottle, and it is a bit higher than outside the bottle as dictated by the tightness of the cap, more gas stays in solution than out. When you remove the cap, the pressure becomes less and to maintain equilibrium at those conditions some gas has to come out of solution. However, if you shake the bottle right prior to removing the cap dislodging gas molecules out of solution then many more will be released.

Hope to have answered your question fully.

Maria

_________________
We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.
T. S. Eliot
Back to top
View user's profile Send private message
nuccia
Beautiful Moderator
Beautiful Moderator


Joined: 28 Jun 2006
Posts: 1743
Location: Canada

PostPosted: Sun Dec 17, 2006 4:59 pm    Post subject: Reply with quote

Thanks Maria...of course you are right.

But you forgot to add one thing...

Make sure his wearing at least one favourite article of clothing or a lucky hat that you really hate when you plan this. Then it will really be worth while! Dancing Dancing Dancing Dancing Dancing

_________________
---nuccia

Only registered users can see links on this forum!
Register or Login on forum!



Only registered users can see links on this forum!
Register or Login on forum!

Back to top
View user's profile Send private message
marisa6
Site Regular
Site Regular


Joined: 30 Jun 2006
Posts: 437
Location: Scotland

PostPosted: Fri Dec 29, 2006 9:36 pm    Post subject: Reply with quote

Hee hee - thanks ladies! I will shake tose bottles up a bit before he opens them next. Hmm - maybe that is what he has been doing to me all along.... Think

Marisa xx
Back to top
View user's profile Send private message
maria
Addicted to this place
Addicted to this place


Joined: 10 Aug 2006
Posts: 532
Location: Connecticut, USA

PostPosted: Fri Dec 29, 2006 10:10 pm    Post subject: Reply with quote

I have been thinking of you Marisa in regards to your oral thesis presentation in January... on maybe not mention it just yet, but wait until after the holidays? One way or another, know that i send you my best...

Maria

_________________
We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.
T. S. Eliot
Back to top
View user's profile Send private message
Debra
Nearly my second home
Nearly my second home


Joined: 29 Jun 2006
Posts: 1219
Location: New Jersey

PostPosted: Sun Jan 28, 2007 11:14 pm    Post subject: Reply with quote

Wow Maria! I have never heard of this happeneing with a microwave and I really appreciate your very interesting explainations!

I love science too! Very Happy

Thank you--it was truly fascinating!!

_________________
"Make yourself familiar with the angels and behold them frequently in spirit,
for without being seen,they are present with you..." ~ St Francis de Sale ~

Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    AMICI OVER THE OCEAN Forum Index -> Health and Home Safety - Salute e Sicurezza domestica All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum



Powered by phpBB © 2001, 2005 phpBB Group
   

Abuse - Report Abuse - TOS & Privacy.
Powered by forumup.it free forum, create your free forum! Created by Hyarbor & Qooqoa
Confirmed

Page generation time: 0.299