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Q & A: Sugar crystals -- using hot and cold water

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Most recent answer: 05/16/2013
Q:
which is better for making sugar crystals hot or cold water?
- jordan
A:
The solubility of sugar in water is higher for hot water than for cold water. You can stir in more sugar in the water if it is hotter. If you dissolve the maximum amount of sugar in hot water, some of the sugar will come out of solution when the water cools off. The sugar will then form crystals on the bottom or sides of the container or on a string hanging in the container.

I remember making big sugar crystals by hanging a string in a cup of sugar water and letting it sit for a few days, evaporating. If you do this, then your water will cool off soon, leaving some crystals right away, and then the rest of the crystals will form slowly as the rest of the water evaporates. You can keep the water hot by doing the whole operation in a pot on the stove.

The sugar crystals you make by boiling away the water may not be as "nice" as the ones made slowly, because the moving water stirs around the crystals as they are forming. You may get lots of little crystals instead of a few big chunks. But the total amount of sugar per cup of water you can get to start with will be higher with the hot water.

Tom

(published on 10/22/2007)

Follow-Up #1: sugar in hot water

Q:
Why does sugar dissolve faster or better in hot water not cold water?
- yaminah (age 9)
garland, tx, usa
A:
Nice question. In a sugar crystal, the molecules stick together well, meaning that they have rather low energy. For a sugar molecule to leave the crystal and go out into the liquid water it has to pick up some energy, because that raises the total energy of the sugar and liquid. What we mean when we say something is "hot" or "high temperature" is that it's easy for its parts to get to high energy. So the hotter the water, the easier it is for a sugar molecule to pick up enough energy to break away from the crystal. So more sugar will dissolve in hot water.

Mike W.

(published on 12/10/2007)

Follow-Up #2: Sugar dissolving time

Q:
will sugar deslove fraster in hot or cold water
- natalhia (age 11)
bakersfield ca kern
A:
A good question.  Why don\'t you do an experiment and tell us the result. Use warm and cold water from the faucet and see how long it takes.

LeeH

(published on 05/16/2013)

Follow-up on this answer.