Solubility refers to the greatest amount of solute that a solvent will dissolve.
Different substances have different solubilities. In addition, three main factors affect solubility.
1. Temperature
2. Pressure
3. The nature of the solute and solvent

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What affect does temperature have on solubility?

Solubility generally increases when the temperature increases. For example, you would heat water up to allow it to absorb more of the solute. Gasses are the exception to this rule, because they are more soluble in cold temperatures.

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What affect does pressure have on solubility?
This is only relevant to gasses, remember. When you increase pressure, you increase solubility. That's what carbon dioxide is filled in drink bottles at high pressure (at about 5 to 10 times the normal atmospheric pressure).

This can be really important for scuba divers! Water pressure increase as you descend, and so does gas solubility. That means that if a diver swims to the surface too quickly, the nitrogen bubbles out of their bloodstream and causes "the bends", a disease that can lead to pain, death, blindness, convulsions, and paralysis. That's why it's important to learn these properties now!

What affect do the natures of the solute and solvent have?
Whether you are dissolving a polar substance in another polar substance, a non polar in a polar, or a polar in a non polar, these will all have an affect on solubility.

Solute: what is dissolved in another substance
Solvent: the substance that does the dissolving

Universal solvent: although water is considered the universal solvent, it won't dissolve non polar substances like oil, which is why oil and water separate whenever you mix them. For non polar substances, methanol and ethanol are great solvents. Substances like soap can help you mix water and oil more successfully.

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1. Which property of water is the main reason it's such an effective solvent?
a) its high specific heat
b) the ease with which it changes state
c) its polar nature
d) its ability to form hydrogen bonds

2. What is known as the "universal solvent"?

3. Polar substances are best at dissolving...
a) polar substances
b) non polar substances

4. When you raise the temperature of a gas, its solubility decreases (T/F).