If you add two tea bags into a tea cup, will more tea dissolve into the water?

Discussion in 'Chemistry' started by InquilineKea, May 25, 2008.

  1. InquilineKea Registered Member

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    16
    So generally you can refill tea bags with hot water several times before the concentration of the tea bags becomes too low to be worth the trouble of filling it up again. So the question is - what equilibrium process prevents the water from becoming dissolved with more tea? Does the water get "saturated" with the tea powder? (can tea powder really be "dissolved?") And if you add two tea bags into the cup, do you shift the equilibrium direction or not? If water gets saturated by tea powder, then I think it wouldn't. but if it was merely a mass exchange process (similar to diffusion), then I would predict that it would.
     
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  3. andbna Registered Senior Member

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    I am pretty sure the water does become saturated with a solute (tea,) and from this, your predictions are correct (with diffusion not being a factor.)
    An interesting way to test:
    Tea is generaly made using water at ~100 degrees(edit: ok, that would be a pretty good rolling boil, maby the kettle doesn't get quite so hot, but I don't drink tea.) Hotter water generaly dissolves much more solute than cold water.
    Therefore, a fully saturated cup of 100 degree tea-water should precipitate tea powder when cooled.
    Try it

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    Assuming my chemistry is right, you should at the very least notice some tea powder in your cup when you reach the end of the drink that was not there before (that is, while drinking it normally.)
    -Andrew
     
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  5. S.A.M. uniquely dreadful Valued Senior Member

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    If you leave the tea bag in the hot water for a longer time, the tea gets more concentrated, so I suspect its just a function of time.
     
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  7. Fraggle Rocker Staff Member

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    Are you guys talking about tea bags, which contain loose tea leaves, or instant tea, which is a powder and a completely different way to make tea?

    Powdered tea simply dissolves and reconstitutes itself. If you use the proper proportions, you will not come close to saturating your water so there will be no precipitation as it cools.

    Tea leaves leach out certain chemicals as they are heated. Caffeine is an obvious one but there are also a number of them that create the flavor and several others like tannic acid. The temperature is important because at too low a temperature some of the chemicals will leach out generously but others will be held back, and your tea won't taste like tea.

    Even at the right temperature, some chemicals leach out faster than others. So if you try to reuse a tea bag, you'll find that it doesn't taste the same the second time. Some of the chemicals got used up the first time.

    The timing is important too. If you leave the bag in the water too long, you'll start to leach out some very bitter chemicals that you don't want in your drink. And if you pull it out too soon, some of the important chemicals won't be there in adequate amount.

    The chemicals leaching out of the tea do not reach saturation point. You can leave the bag in for ten minutes and you'll keep getting more of many of them. You can also put three or four tea bags in one cup and you'll get something so strong you won't want to put it in your mouth. That's the typical way to make iced tea: Make it stronger than normal, so when it's diluted by all the melting ice it will taste just right.
     
  8. Read-Only Valued Senior Member

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    10,296
    Like any other substance dissolved in water, there is a saturation point. Two or more bags won't result in any more dissolved tea (stronger) but it will cause it to become stronger (more saturated) quicker.
     
  9. Syzygys As a mother, I am telling you Valued Senior Member

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    This is incorrect or at least an overgeneralization. Depends on the quantity of teabag and water compared to each other. What you said might be true for some teas, and incorrect for others.
     
  10. Read-Only Valued Senior Member

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    Yes, it's correct for the same amount of time, and that seemed to be the general assumption since it will always get stronger the longer you go. Sorry, I failed to include that.

    By the way, Fraggle gave the most complete answer - mine was intended to be just the short and quick version. Not enough time to write a whole manual.

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  11. iceaura Valued Senior Member

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    There are a few factors operating concurrently - the water is cooling, the tea stuff leaches out faster in hotter water, the chemical balance of stuff leaching changes over time as well as temperature.

    So beyond a certain point, you aren't getting much better or stronger tea by waiting. Like cooking anything - stop when its done.

    Some teas - notably some oolongs - leach slowly enough while the water cools that the initial infusion has made as good a tea as you are going to get while there is still lots of stuff in the leaves. These teas make good tea for two, even three infusions with newly heated water.

    And the water for those teas usually shouldn't be quite as hot as the boiling stuff you want for regular black tea. It changes the balance of the dissolved chemicals.
     
  12. InquilineKea Registered Member

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    16
    Thanks so much for the answers!

    Hey fraggle, what keeps the water from becoming saturated with tea then? (if a lot of the powder isn't used up - after all - the powder is oftentimes usable for a second or third time). And if you can reuse a tea bag ~3 times (or maybe more), then if you add 3 tea bags, could you reuse them for the same number of times as well?
     
  13. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    The nice tasting stuff in the tea diffuses out first.
    If you leave a tea bag for a long time,
    the tea will be strong but taste very harsh.
     
  14. John99 Banned Banned

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    22,046
    No it is correct. Once saturation point is reached the tea will stay contained to the bag. Whatever the number to reach saturation may be.

    The easiest way to look at this may be like this:

    Take an empty bag and add a smaller bagful of fine dirt to it. The bags of dirt are jiggled from a mesh type bag suspended within the larger bag. The small dirt bags empty, so you do it over and over but at some point the dirt will stay inside of the smaller bags because there is no more room left in the larger bag to accommodate the dirt.

    HTH's
     
    Last edited: May 27, 2008
  15. Positron Agony: Not all pain is gain Registered Senior Member

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    if we are just talking about powder, that is assumed to be entirely soluble, then the powder will dissolve until the water is saturated, if you are talking about like herbsin a bag, then the parts that can dissolve do, and the harder organic structures remain, provided the water does not reach a saturation point.
     
  16. Syzygys As a mother, I am telling you Valued Senior Member

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    12,671
    But that is the KEY point: whatever the saturation point may be. I said it depends on the tea. You are ASSUMING that any kind of teabag completely reaches the saturation point. We just don't know and most likely they don't, thus if a particular kind of tea needs 2 or even 3 bags to reach the saturation point, than 2 bags will make it stronger, assuming the same time and temperature....
     
  17. InquilineKea Registered Member

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    16
    Oh, I think I get it. Does solute take longer to dissolve the MORE saturated the water is? As in, inverse relationship between dissolvation rate [d[Solute]/dt] and concentration of solute? [Solute]
     
  18. Syzygys As a mother, I am telling you Valued Senior Member

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    12,671
    Probably yes, but it is not just that. In the first few minutes the tea dissolves rather quickly, but than it takes more time or higher temperature even if you used running water (thus saturation wouldn't be possible). I assume the Dissolution/time graph is a parabolic one, thus the dissolving start out quickly and start to get slower and slower as time passes, again with hot water.
    With cold water it could be different, but I am not a chemist...Certain teas need to be made over a longer period of time not to harm the ingredients in the tea with high temperature...
     
  19. John99 Banned Banned

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    yes but i think the same principles apply even if you change conditions such as temperature etc.

    He asked:

    The answer i would say is obviously yes. Of course that is with all things being equal and normal as far as what we consider to be normal.

    Of course time is a factor, in the short term and if time was limited then you would have both bags releasing tea. IOW both bags working. The question is a little vague and does not give any specific conditions though.
     
  20. Forceman May the force be with you Registered Senior Member

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    Dissociation

    One of the key points in dissoliving is to consider the type of substances interacting.Water is polar and the tea powder is covalent, a bad mix if you are trying to make a homegenous mixture(solution). The tea poweder molecules will not be dissociated because there isn't a sufficient amount of van der waal forces acting on between the molecules. Water generally dissolves polar and ionic compounds-like and like, rather than like and opposite. So the saturation point(quantizationally speaking) would be extremely high, and therefore at normal temperatures of your oven,microwave,etc, equilibrium would not be uniformly met, but I must say at a pretty high temparuture and for a long period of time the tea and water would resemble a system of equilibrium which would make the perfect tea. So in conclusion I must say that the water is saturated, but techniallly not saturated chemically speaking, but objectivelly and disputely, from a on-hand bird-eye view, it would appear to be saturated, and adding more would cause the tea to be in a low state of entropy, unless of course you increase the temparuture, and of course you have to include the amount of water.
     
  21. Kayyam Registered Member

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    4
    Suppose you leave a tea bag in for a long time - say an hour. During this time you keep the water hot. Eventually you do obtain a saturated solution in which all of the chemicals that leach out of the tea leaves are present at their respective saturated concentrations.

    Now you drink this awful cup of tea and replace the hot water.

    Yes, more of the chemicals do leach out of the tea leaves into the fresh water because of Le Chatelier's principle. The water has zero concentration and the leaves have at least some infinitesimal concentration so it must re-equilibrate. Your second cup will be weak and will have different proportions of each chemical.

    Thermodynamics does not tell us which cup will taste better

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    /Kayyam
     
  22. whitewolf asleep under the juniper bush Registered Senior Member

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    It can't be at 100C in the cup. It boils in the kettle for sure, but it doesn't boil in the cup, and the cup itself is cold. So, um, we never place tea bags into boiling water.
     
  23. Oli Heute der Enteteich... Registered Senior Member

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    100F?
    Nowhere near boiling

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