Name ________________________________________ Date _________ Per ____ Doc ____
Solubility
Rhonda wanted to see if salt or sugar dissolves faster in water. She
added the same amount of salt and sugar to a half liter of room
temperature (20 °C) water in separate glasses. Then she stirred both
mixtures. All of the sugar dissolved in less than a minute, but after 5
minutes of stirring, some of the salt still hadn’t dissolved. Even if she had kept stirring the
saltwater mixture all day, the remaining salt would not dissolve. Do you know why? The answer
is their solubility.
Solubility is the amount of solute that can dissolve in a given amount of solvent at a given
temperature. In a solution, the solute is the substance that dissolves, and the solvent is the
substance that does the dissolving. For a given solvent, some solutes have greater solubility than
others. For example, sugar is much more soluble in water than is salt. But even sugar has an
upper limit on how much can dissolve. In a half liter of 20 °C water, the maximum amount is
1000 grams. If you add more sugar than this, the extra sugar won’t dissolve. You can compare
the solubility of sugar, salt, and some other solutes in the table below.
Solute
Grams of Solute that Will Dissolve
in 0.5 L of Water (20 °C)
Baking Soda
48
Epsom salt
125
Table salt
180
Table sugar
1000
Q: How much salt do you think Rhonda added to the half-liter of water in her experiment?
Explain your reasoning.
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Factors that Affect Solubility
Certain factors can change the solubility of a solute. Temperature is one such factor. How
temperature affects solubility depends on the state of the solute, as you can see in
the Figure below.
If a solute is a solid or liquid, increasing the
temperature increases its solubility. For example,
more sugar can dissolve in hot water than in cold
water.
If a solute is a gas, increasing the temperature
decreases its solubility. For example, less carbon
dioxide can dissolve in warm water than in cold
water.
The solubility of gases is also affected by pressure. Pressure is the force pushing against a given
area. Increasing the pressure on a gas increases its solubility. Did you ever open a can of soda
and notice how it fizzes out of the can? Soda contains dissolved carbon dioxide. Opening the can
reduces the pressure on the gas in solution, so it is less soluble. As a result, some of the carbon
dioxide comes out of solution and rushes into the air.
Q: Which do you think will fizz more when you open it, a can of warm soda or a can of cold
soda? Explain your reasoning.
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Summary
Solubility is the amount of solute that can dissolve in a given amount of solvent at a given
temperature. Some solutes have greater solubility than others.
Temperature affects the solubility of solutes in all three states. Pressure also affects the solubility
of gases.
Critical Thinking Questions
Using the link below, watch the video about solubility and then answer the following questions.
http://www.youtube.com/watch?v=IKimraU21ws
1. How does Mr. Anderson define solubility in the video? _______________________________
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2. What is the solubility of talc in 100 mL of 25 °C water? Explain why talc has this solubility.
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3. Describe how increasing temperature affects the solubility of solid and liquid solutes.
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4. Why is there less oxygen in ocean water near the equator than in water at higher latitudes?
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5. A factory discharges clean, warm water into a nearby stream. Fish keep dying in this part of
stream. Explain why.
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8. You open a can of room temperature soda and pour it into a glass. Why does the soda go flat?
Will it go flat faster or slower if you add ice? Why?
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(from https://www.saddlespace.org/whittakerm/science/cms_page/view/7795249 )