# Adding xylitol to hot water lowers the boiling point and makes it boil

• Jonathan212
In summary: What does boiling point mean?Boiling point is the temperature at which a liquid boils.What does freeze point mean?Freeze point is the temperature at which a liquid freezes.In summary, when adding xylitol to water, the boiling point is raised and the freeze point is lowered.
Jonathan212
This probably occurs with salt too but let's concentrate on xylitol: you heat water till it boils, put the hot water in a cup and add a tsp of xylitol. It boils again violently for a couple of seconds. The high school explanation is that the boiling point of the water is lowered. I'd like to know what happens in terms of energy, and at the molecular level: as in, you have 1000 molecules of water vibrating and a molecule of xylitol gets close. Why would the neighbouring water molecules vibrate more next to xylitol?

You can't really get a good picture of collective effects (like phase transitions) by focusing on individual molecules.

What is at play is the Gibbs free energy (G) of the different phases. Water will go from liquid to gas at 100 °C because at that point the G curves of the liquid and gas cross, and Ggas < Gliquid for T > 100 °C.

Adding a solute only affects the liquid phase (since the solute will not be present in the gas), so it changes the point where the curves cross. See the nice graphs at
https://chem.libretexts.org/Bookshe..._Some_Applications_of_Entropy_and_Free_Energy

One might guess that some energy is released when dissolving xylitol in water, raising the temperature of the water solution. Enough to make liquid reach the boiling temperature for the mixture? Not sure myself.

I would imagine better, that adding any solute to solvent (water) would INCREASE the boiling point and DECREASE the freeze point. We can wait for other members who have a better familiarity with xylitol-water solutions.

Exactly the same thing happens with salt. Is it really a physics problem if you're trying to predict what will happen if a single molecule of salt falls through air molecules till it hits water molecules?

It is more about activation energy required for bubble building, and not limited to xylitol.

Saturated vapor pressure depends on the interactions between liquid molecules. When the phase interface is flat, molecules interact with others occupying exactly half the full solid angle. Depending on whether the surface is convex or concave there are more or less intermolecular interactions and saturated vapor pressure goes up or down (think capillary condensation).

When you add any solid into the water it initially has plenty of convex and concave places, were water gets curved, hence it starts to boil quickly.

If you have a good stainless steel pot with smooth walls put some water into, heat it till it almost boils, then add a pinch of salt. Pufff! And if you keep heating, adding rice or groats later will produce the same effect again. Just keep some rag ready

Edit: Jonathan212 beat me about the salt part.

What exactly does dissolving mean when we're talking about xylitol? It does not turn into ions does it?

No it doesn't. Dissociation is not an obligatory part of the dissolution process.

symbolipoint

## 1. What is xylitol and how does it affect the boiling point of water?

Xylitol is a type of sugar alcohol commonly used as a sugar substitute. When added to hot water, xylitol molecules disrupt the hydrogen bonding between water molecules, causing the boiling point to decrease.

## 2. How much xylitol should be added to hot water to lower the boiling point?

The amount of xylitol needed to lower the boiling point of water depends on the quantity of water and the desired decrease in boiling point. Generally, a concentration of 1-2% xylitol is enough to lower the boiling point by 1-2 degrees Celsius.

## 3. Can xylitol be used to make water boil faster?

No, adding xylitol to hot water will actually lower the boiling point, which means it will take longer for the water to reach its boiling point. This is because the xylitol molecules disrupt the hydrogen bonding between water molecules, making it more difficult for them to break free and turn into steam.

## 4. Are there any other substances that can lower the boiling point of water?

Yes, there are several substances that can lower the boiling point of water, such as salt, sugar, and other sugar alcohols like erythritol and sorbitol. These substances all disrupt the hydrogen bonding between water molecules in a similar way to xylitol.

## 5. Can xylitol affect the taste or properties of boiled water?

When used in small amounts, xylitol should not significantly affect the taste or properties of boiled water. However, using too much xylitol may result in a slightly sweet taste and a stickier texture. It is important to note that xylitol should not be consumed in large quantities as it can have laxative effects.

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