The slower you heat tea up...the longer it stays hot...

[mossman]

Does this mean anything to you guys?

[IronFist]

I hope you don't mean that literally.

And if you don't, because it's not true, it's therefore a bad analogy to any conceivable situation.

[mossman]

no. an old chinese man told me, what did he mean?

[IronFist]

He probably means don't rush things.

[Ford Prefect]

That old chinese man must write for the fortune cookie company that I get my chinese food from.

[norther practitioner]

Originally posted by mossman
Does this mean anything to you guys?

Do I need to drop some Thermodynamic knowledge on your arse?

Yes it means don't believe everything you hear.

[Chief Fox]

No, it means if you heat tea too quickly, you could burn it.

[IronFist]

Originally posted by Chief Fox
No, it means if you heat tea too quickly, you could burn it.

No it doesn't. If it meant that they would just say that.

[Chief Fox]

Originally posted by IronFist
No it doesn't. If it meant that they would just say that.

good point.

[FngSaiYuk]

How about this-

If you define 'hot' to be 100C
And we define 'heat up' to mean bring from 20C - 120C
And we define the time for how long it stays hot the length of time it takes from the point the temp of the tea reaches 'hot' (or 100C) and above, to the point when it cools down below our 'hot' threshold
And we assume all other equal conditions for cooling down

THEN.... if we take the time to heat it up to 120C, then the the delta of time between the point when the tea is heated to our hot threshold of 100C and the time we stop heating it up (bring it to 120C) and it cools back down to below 100C will be longer if the time we take to 'heat' it up between our 'hot' point and our cut off point of 120C is longer.

OK, try to make sense of THAT

::grin::

[Ming Yue]

I think the old guy was just trying to be esoteric.
old chinese guys will do that.

[Vash]

I think he was talking about seducin' yo' woman.

Work on that foreplay for a few hours, then du-Yam!

[IronFist]

But if you stop smoking crack, water will cool at the same rate regardless of how quickly it was heated.

The only exception I can think of would be if there was some material for which a slow heat (longer exposure) caused it to change somehow to a different material that held heat longer, and if you heated it up quickly it would not undergo the same chemical change, but that's not what we're talking about here. I don't even know if such a material exists. Physics/chemistry people?

[mickey]

Greetings,

I remember hearing someone say that microwaved food cools off faster. Maybe there is some truth to the statement.

mickey

[FngSaiYuk]

Originally posted by IronFist
But if you stop smoking crack, water will cool at the same rate regardless of how quickly it was heated.


Yes yes, but the point is, if you have a fixed temp that you're heating to and that target temp is higher than the temp that you'd consider 'hot', then since the water cools at the same rate from the target temp, you potentially have a longer period at which the water is 'hot' if you heat it slowly enough that there's a time difference between reaching the 'hot' temp and the target temp.

Here's a break down of an example-

temp range normal heating slow heating
20C - 100C 90sec 120sec
100C - 120C 20sec 45sec
120C - 99C 600sec 600sec
HOT ( > 100C) 620sec 645sec

so in this case, for this particular definition of HOT, the slower we heat the tea, the longer it's hot

of course I'm totally ignoring the word 'stays' ::grin::

[Samurai Jack]

Yeah, if you're waiting for the water to boil and you have it set on "warm", then it could take all day for the pot to boil, which would technically mean that it's hot for a longer period of time than if you you had set it on "high".

Them Old Chinese guys are tricky sometimes. Who knows what he meant? Maybe he was just trying to explain how to keep your tea hot in between drinking sessions.

Which reminds me, I really should start POSTING between drinking sessions.

[Toby]

Originally posted by mickey
I remember hearing someone say that microwaved food cools off faster. Maybe there is some truth to the statement.Maybe. I think that's probably due to microwaves heating food unevenly.

The old guy's comment is crap. Two equal volumes of water both containing the same amount of heat will cool at the same rate given equal pressure and ambient temperature conditions. If both volumes are boiling before the heat source is taken away, then both will be at the same temperature and contain equal heat capacity. You can't get the water hotter than boiling because it'll change state*.

*You can get it hotter than boiling point by superheating, interestingly in a microwave. But that'd be heating the tea up quicker ;). Or you could change ambient conditions, i.e. atmospheric pressure and temperature. Maybe the old guy means if you heat it long enough ambient temperature will go up and therefore heat loss will be slower :D.

[IronFist]

Originally posted by Toby
*You can get it hotter than boiling point by superheating, interestingly in a microwave.

Yeah, and then it blows up in your face when you try to stir it (did you see those stories on the news?) :eek:

[Toby]

Yeah, I've only managed to do it once, but I knew what to expect and I was careful. I was trying to do it.

[IronFist]

You need to use a container that is perfectly smooth, right? Because don't little bumps in the sides initiate the boiling action?

Do you know at what temperature it becomes "superheated?"

[Toby]

Originally posted by IronFist
You need to use a container that is perfectly smooth, right? Because don't little bumps in the sides initiate the boiling action?Yeah. Forget what I used. It also helps if you remove the spinning plate and set the vessel down so it's not moving ;).

Originally posted by IronFist
Do you know at what temperature it becomes "superheated?" Anything over 373.135K :D.

[Ford Prefect]

Perhaps the extra time it takes for him to heat the tea slowly allows him a moment to go get a thermace or other insulated container...

[fa_jing]

Right, at standard atmospheric pressure water turns to steam at 100C. There is an energy expenditure associated with heating it to the boiling point, then a sizeable additional energy expenditure required to convert the boiling water into steam. The more heat you apply to the water once it reaches the boiling point, the more water is converted to steam, but the water stays at 100C until all of it is converted. Steam, on the other hand, can be raised past the 100C temperature.

Now, what is "superheating?"

[fa_jing]

http://www.phys.unsw.edu.au/~jw/superheating.html

nevermind