Why Does Adding Powder to a Hot Liquid Make It Boil?

Frank, you mentioned nucleation, so GA for you!

I had heard one time about a boy who suffered major burns because of this. Being skeptical I actually tried to get this to happen (may be foolish, but I didn't hold my face over the "loaded gun"). The only thing I have ever gotten it to do is fizz a little when I throw in the tea bag. Has anyone ever seen a cup of hot water actually erupt?

in directly, but other than that i only repeat what I hear..........

I have not done this, but I have heard that the eruption thing really only happens when you use a container with a smaller opening compared to the surface area. Distilled water and a glass bottle also help, try with a glass soda bottle or ice tea bottle and see what you can get.

Just be careful not to get burned.

This really does happen, I've purposely done this to demonstrate the potential danger to a friend of mine that was in dis-belief that it was possible. Technically it is (as previously stated) because the smooth surface lends no edges/pores to help form the vapor bubbles. Microwave a glass of water (in a good scratch-free microwave safe ceramic cup) for a couple minutes on high, and (wearing appropriate PPE, and taking every safety precaution) drop in some objects with porous/sharp surface areas (try salt) and watch the result. the water instantly boils!

salt also lowers the boiling point.

Yup sure does, you can use anything you want, Sugar, Coffee, rice, oatmeal etc. Salt just gets the best reaction for demonstration purposes, it helps with the WOW factor.

Salt raises the BP.

Blood Pressure?

Hello phoenix911,

Sorry my friend but any substance solved in water increases the boiling point and decreases the freezing point. In fact it happen with any pure solvent and any solute. It's and old chemistry law. I made some experiments while I was student (I can't remember dates). This principle is used to determine molecular weight of substances.

These temperature shifts depend on the solute properties (molecular weight, concentration, solvent, Van't Hoff index, etc)

And one proof surely everybody have seen: To deice roads which substance use to be added? Salt

I agree with the explanation of increasing the nucleation points.

Kind regards

Kwetz

crying out loud, I knew that, heck thats how they decreased the time for canning.

Along with that, Salt added to water (brine), decreases (lowers) the freezing point in water (brine). depending on the concentration to about 28 degrees F, coincides with you statement.

And one proof surely everybody have seen: To deice roads which substance use to be added? Salt

but, except when the temperature drops to 0 F. its not as active.

This principle is used to determine molecular weight of substances.

Being in the food and dairy business, I've designed Ultra Filtration units to clarify the brine. must not have been on top of my game yesterday.

Sorry I'm desperately trying to redeem myself.............

Thank you for the correction and my sincere and humbled apologizes.

phoenix911

small opening not always true. heat a cup of water in the microwave to boil. add instant coffee. dump in a helping of sugar, and stand back. I expect that the amount of sugar makes some difference since this does not always produce a boil. I suppose that as the water gets nearer the saturation point the boiling temp is lowered. by the way this was observed at about 2500 ft above sea level.

Frank 20. would you please contact me directly on an unrelated subject.

mag623@telus.net

Yes, I had it happen to me on occasion with a microwaved cup of water. Almost scalded myself when it happened unexpectedly, so I am extremely careful now.

I think that because dissolved substances as sugar and salt increase the BP of the water, hence requiring higher temperature because of a need for high internal pressure for bubble nucleation, what may be happening - I postulate - is as follows: Each sugar grain or salt grain upon introduction into the liquid reduces the internal pressure in the immediate vicinity of the grain. This lower pressure within a hotter fluid then causes some kind of microscopic cavitations, these microscopic cavitations so formed then undergo rapid coalescence as the grains dissolve rapidly leading to sustainable bubbles formation with attendant implosion and hence the seeming boiling phenomena.

In the cases of nonsoluble substances the formation of nucleation sites on the solids - as discussed by some others above - may be the effective causes.

I don't know about non-solubles, never having tried them, but I wonder if there is not a certain amount of oxygen, or other active gases, released from the soluble grains (sugar molecules entrain a lot of oxygen and carbon, look at the formulae), which TEMPORARILY drop the local boiling point. I do notice that the boil up is very rapid in both onset and decay, unlike that achieved when water (or tea, milk, coffee, sugar syrup, even) is merely brought to a rolling boil without subsequent addition of adulterants, wherein the boil is slow to occur, long-lasting (relatively speaking) even after removal from heat, etc.

It may be entirely due to nucleation points, but if they are the explanation for the achievement of a rolling boil without the addition of other materials, I don't think they could account for the rapidity of onset or decay WITH the addition, since they don't cause it without the addition. Try it in a worn and pitted pot, and, while the onset of a rolling boil MAY be somewhat quicker than in a new/pyrex/unworn/unscratched/etc. pot, I haven't noticed it being substantially quicker to either rise or decay. Of course, I'm working from memory on some of this, so others may have observed it with a more critical eye, and may be better reporters.

Mike

Champagne has the same issue. When modern vineyards tried to make sparkling wine they over filtered it and the bubbles did not act right.

When they checked the differences the fine dust was missing from their Nouveau champagne.

It seems the dust was the nucleation points for the trails of bubbles. No dust, eruption but no trails of bubbles.

Brad

I also read this, but I wonder does the Champagne taste any different if it is not bubbling or bubbling because of the dust. If there is no dust and it is not bubbling, will it start to bubble in your mouth and not in the glass? Would that make it taste different? Will it eventually bubble out or go flat like a soda left out for a long period? Does orange juice added to Champagne to make a Mimosa cause bubbling? Does it stop bubbling after a while? If it does can you add more OJ to make it bubble again?

Hello sail4evr,

...does the Champagne taste any different...?

Yes, (though many would not notice) A hard foam in the mouth while the dust makes it a soft tickle. I'm very picky about Champagne because 98% of it I can't stand Sometimes being a super taster is a curse. Next fall I'll be the Vintner for my cousins vineyard. Now that is a job for the taste buds.

Can most people taste the difference? I don't know. I do know I can.

Brad

I have had a cup of water boil explosively after microwaving and adding milk powder.

While I am sure the major effect is nucleation, it should also be noted that as a granular material sinks, it alternately sheds a vortex side to side behind it, giving a local pressure reduction which can be significant even for fairly low velocities of sink. This can cause flash boiling immediately behind the grain, attaching to the grain and nucleating from it.

The effect of the solution raising the boiling point would occur only after material has dissolved. Generally, this would be too late to affect the boil over we are talking about.

Because a dissolving grain will be subject to dynamic chnages of the surface crevical structures, there should be no well-defined crevices to support the heterogeneous nucleation phenomenon as being suggested, rather the local reduction of pressure should effect the formation of bubble formation, but then such formation due to internal local pressure differences would be of the form of microscopic cavitations that coalesce into bubbles as I have earlier explained. The dominant physics here as has also been noted by some others is the consequential reduced local pressure. Dissolving grains without well-defined surface crevices can not support heterogeneous nucleation as suggested. The competitive dynamics between heterogeneous nucleation and homogeneous nucleation [- the latter being of the form of cavitation] in the vicinity of the dissolving grain favours the latter.