Is it possible to smell which liquid has more sugar dissolved?

[firewolfsm]

Now, my sister thinks that she can smell how much sugar there is in tea, that she can distinguish between 1 tbsp and 8 tbsp. We tried this and she actually got it wrong, which made her shut up.

Now I know a molocule needs to have sufficient nuclear mass to stimulate neurons in the nose and that sugar definitely doesn't enough mass for that.

That was the reason my dad gave for not being able to smell it, which works. My idea however was that for you to smell it, the sugar needs to leave the water and move freely in the air so it can reach your nose. I assumed sugar can't evaporate with the water until my dad said it actually does.

So my real question is, if you have something dissolved in heated water, does any of it actually escape with the water molecules that hydrated it?

 

[CycloWizard]

Depends on what's in the water. In the case of sugar, it will stay in until just about all of the water is gone. In the case of, say, ethanol, they will come out together in a very complicated manner. This is due to the interactions of the two polar molecules, causing the formation of an azeotrope. Thus, the relative fractions of ethanol and water that are coming off at a given time depends on the current ratio in the liquid, as well as the temperature.

 

[Gibsons]

Originally posted by: firewolfsm
Now, my sister thinks that she can smell how much sugar there is in tea, that she can distinguish between 1 tbsp and 8 tbsp. We tried this and she actually got it wrong, which made her shut up.

Now I know a molocule needs to have sufficient nuclear mass to stimulate neurons in the nose and that sugar definitely doesn't enough mass for that.

That was the reason my dad gave for not being able to smell it, which works. My idea however was that for you to smell it, the sugar needs to leave the water and move freely in the air so it can reach your nose. I assumed sugar can't evaporate with the water until my dad said it actually does.

So my real question is, if you have something dissolved in heated water, does any of it actually escape with the water molecules that hydrated it?

I think the reason is the little if any of the sugar leaves the water to reach her/your nasal passages (it's not volatile). It can't be nuclear mass because there are molecules much smaller than sugar which have a mighty stench.

Beta mercaptothanol has a mass about half that of glucose, but you open a bottle of it and people several feet away will smell it in no time. Then there's the horrors of butyric acid, also about half the mass of glucose. Imagine if you collected the socks of every pro football team for a whole year, let them fester in a closet for a few days and then concentrated the stench into one small bottle.

 

[silverpig]

Originally posted by: Gibsons

Originally posted by: firewolfsm
Now, my sister thinks that she can smell how much sugar there is in tea, that she can distinguish between 1 tbsp and 8 tbsp. We tried this and she actually got it wrong, which made her shut up.

Now I know a molocule needs to have sufficient nuclear mass to stimulate neurons in the nose and that sugar definitely doesn't enough mass for that.

That was the reason my dad gave for not being able to smell it, which works. My idea however was that for you to smell it, the sugar needs to leave the water and move freely in the air so it can reach your nose. I assumed sugar can't evaporate with the water until my dad said it actually does.

So my real question is, if you have something dissolved in heated water, does any of it actually escape with the water molecules that hydrated it?

I think the reason is the little if any of the sugar leaves the water to reach her/your nasal passages (it's not volatile). It can't be nuclear mass because there are molecules much smaller than sugar which have a mighty stench.

Beta mercaptothanol has a mass about half that of glucose, but you open a bottle of it and people several feet away will smell it in no time. Then there's the horrors of butyric acid, also about half the mass of glucose. Imagine if you collected the socks of every pro football team for a whole year, let them fester in a closet for a few days and then concentrated the stench into one small bottle.

Methanol...

 

[Mark R]

The molecular mass isn't really relevant - ammonia is extremely, err..., fragant, but it's molecular mass is less than that of water.

To have a detectable smell, it must:
1. Vaporize, or otherwise enter the air, so that it can reach the olfactory neurones in the nose
2. Activate a receptor on a specific neuron. Not all substances activate olfactory neurones, even if they reach them (e.g. methane doesn't, but ammonia does); not all people have the same selection of olfactory receptors (e.g. there are specific genes that produce certain types of olfactory receptor, and an individual with a defective gene will not be able to smell that particular substance. E.g. approx 0.1% of people cannot smell butyl mercaptan (skunk), 10% cannot smell hydrogen cyanide, 12% cannot smell musk (perfume ingredient)

 

[Paperdoc]

Mark R is right on, but I'd add one point. Virtually everything vaporizes to some extent or other. The question really becomes, how much? And that's where Mark R's Point 2 comes in. Some receptors in the nose just are not as sensitive as others. Or maybe, the same receptors can detect different things, but have very different sensitivities to different chemicals - I'm not sure which. Anyway, to be detected by the nose, the concentration of glucose molecules in the air entering the nose would have to be above the minimum threshold for detection. Apparently what little vaporized above a cup of tea with up to 8 tbsp (tablespoons? really?) of sugar is not enough for your sister's nose to detect. Or, more precisely according to your post, she was unable to detect the difference between two cups of tea with different amounts of sugar.

By the way, I maintain that I can smell sugar if I sniff the sugar bowl. Now, that's much more concentrated and likely there is more sucrose vapor over the solid crystals. But also, in that case there is no tea smells to confuse my nose, and that may be a factor, too.

 

[PlasmaBomb]

What Paperdoc is referring to is vapour pressure (in case you want to look it up).

As for smell, it developed along side taste, which is why it is likely that certain things have recognisable smells - as it serves as a warning.

For an idea of how important smell is to taste have a look at this graph - the recognisability of everyday objects drops dramatically if you lose your sense of smell. That's also one of the reasons why when you are ill and loose your sense of smell your sense of taste and appetite drops.

Sugar will actually lower the vapour pressure of water (Raoult's Law: P = Po x xa, where P is the vapour pressure, Po is the vapour pressure of pure solvent, and xa is the mole fraction of the solvent), and in doing so may lower the vapour pressure of other volatile organic compounds. Thus you could possibly detect the presence of sugar by the reduced smell of 'tea', although it may work better with coffee.

Edit: added Raoult's Law for anyone interested

 

[killster1]

i think there are way to many variables to do just one test.. i say i can smell it too but not at the bottom of a cup.. but stirred up in the cup (freshly stirred) also diff types of tea may help / hurt as others mention.. (cant believe i read this))