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Home School Life Journal ................................................................................................................painting by Katie Bergenholtz

The Effects of Temperature on Solubility

Solubility- The maximum amount of solute that can dissolve in a given amount of solvent.
Solute-The substance being dissolved in order to make a solution.
Solution-The result of one or solutes being dissolved in a solvent.
Solvent- The substance in which the solute is being dissolved in order to make a solution.
Saturated solution-A solution in which the maximum amount of solute has been dissolved.

The Effect of Temperature on the Solubility of Solid Solutes
For this experiment, you will need a canning jar (or beaker), 1/4 cup measuring cup, a stove, a candy thermometer, a coffee filter (or filter paper), a saucepan and a funnel



Put 1/4 of salt and 1/4 cup of water in a saucepan. Set up your filtering system by putting a funnel in a canning jar or a glass measuring cup. Heat the salt-water mixture until it reaches 95 degrees F. Pour the solution into the filtering system until you a clear solution.  It should be clear because all undissolved salt should have been filtered out by the filter paper. This is a saturated solution of table salt.  Now place the solution in the freezer for about 20 minutes. Remove from the freezer and examine. There should be crystals of salt lying on the bottom of the canning jar. (Sorry I neglected to get pictures of this experiment once we got going. We cleaned up before I remembered!)

What happened?
The solubility of a solute depends on temperature. For solid solutes, the solubility increases with increasing temperature. In order for a solid to dissolve, the solvent molecules must be able to muscle in between the solute molecules and drive them away from each other. The heat provides the energy needed to make the solvent molecules more successful at muscling in between the solid molecules.

The Effect of Temperature on the Solubility of a Gas
For this experiment you will need a saucepan and either a metal bowl or another saucepan, a canning jar (or test tube), ice and a carbonated soda.

Can you see the soda bubbles popping on the surface around the edge of the jar?

Fill the saucepan 1/2-3/4 full of water. Heat until it begins to boil. While you are waiting for the water to boil, fill the bowl or other saucepan 1/2 full with ice and then add enough water so that it is 3/4 full of cold ice water. Once the water in the first saucepan is boiling, turn it down to a low temperature so that it remains warm but not boiling too hard. Fill a canning jar 3/4 full of soda. Set this into the hot water. Observe what happens. In a few moments, once the soda warms, it will begin to bubble as the carbon dioxide is released.

When the same soda is placed in a bowl of ice water, the bubbles stop forming and popping on the surface.
Now place it in the bowl or saucepan with ice water. In a few moments, the soda should stop bubbling.

When you put it back into the hot water, the bubbles start forming again.

After a moment, return the canning jar to the hot water. The soda in the canning jar should start bubbling again. Repeat this process a couple of times and each time the soda is put in the hot water, it should release more bubbles and each time it is put in the ice water, it should stop bubbling.

What happened?
Soda has the gas carbon dioxide dissolved in it and so is a solution made of a gaseous solute into the soda, which is a liquid solvent. By putting the canning jar of soda in the hot water, we were increasing the temperature of the solvent, making the carbon dioxide less soluble and therefore it had to leave the solution.
On the other hand, when the jar went into the cold water bowl the temperature of the solvent was lowered. This caused the solubility of the carbon dioxide to increase, so no gas had to escape the solution, and so the bubbling ceased.  Unlike solid solutes, gaseous solutes are less soluble that in hot solvents than in cold ones.


What about liquid solutes? The temperature of the solvent has little effect on the solubility of the solute, so has little effect on the process of dissolving a liquid solute in a liquid solvent.

source: Exploring Creation with Chemistry, Jay Wile

4 comments:

  1. I like the use of soda in this experiment!

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  2. My kids would love this. Nice experiment! Thank you for sharing.

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  3. I could have sworn I commented on this!

    Oh well, now I am. I love all of the different ways you make chemistry hands on. It really gets me thinking.

    Oh, and that reminds me I need to go back to your ancient history posts to see if there's anything coming up we need to use.

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  4. Great kitchen science experiment. Anything involving soda is always fun.

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