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Substances that dissolve most readily in water include ionic compounds and polar covalent<br />
compounds.<br />
Electrolytes and Nonelectrolytes<br />
Electrolyte: A compound that conducts an electrical current when it is in an aqueous solution or in the<br />
molten state; all ionic compounds are electrolytes, but most covalent compounds are not.<br />
Nonelectrolyte: A compound that does not conduct an electric current in aqueous solution or in the<br />
molten state<br />
Strong Electrolyte: A solution in which a large portion of the solute exists as ions<br />
Weak Electrolyte: A solution that conducts electricity poorly because only a fraction of the solute<br />
exists as ions.<br />
Conduction of an electric current requires ions that are mobile and, thus, able to carry charges<br />
through a liquid.<br />
All ionic compounds are electrolytes because they dissociate into ions.<br />
Many molecular compounds are nonelectrolytes because they are not composed of ions.<br />
Some compounds are not electrolytes in their pure state, but with water, they become<br />
electrolytes.<br />
Connection: Gatorade and Powerade, as well as other sports drinks, are loaded with<br />
electrolytes to supposedly help the athlete in their events.<br />
Hydrates<br />
Water of Hydration: Water molecules that are an integral part of a crystal structure<br />
Hydrate: A compound that has a specific number of water molecules bound to each formula unit<br />
Anhydrous: Describes a substance that does not contain water<br />
Effloresce: To lose water of hydration; the process occurs when the hydrate has a vapor pressure<br />
higher than that of water vapor in the air<br />
Hygroscopic: A term describing salts and other compounds that remove moisture from the air<br />
Desiccant: A hygroscopic substance used as a drying agent<br />
Deliquescent: Describes a substance that removes sufficient water from the air to from a solution; the<br />
solution formed has a lower vapor pressure than that of the water in the air.<br />
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When crystals are heated above 100 O C, they lose their water of hydration.<br />
The forces holding the water molecules in hydrates are not very strong, so the water is easily<br />
lost and regained.<br />
If a hydrate has a vapor pressure higher than the pressure of water vapor in the air, the<br />
hydrate will lose its water of hydration.<br />
15.3 Heterogeneous Aqueous Systems<br />
Suspensions<br />
Suspension: A mixture from which some of the particles settle out slowly upon standing<br />
A suspension differs from a solution because the particles of a suspension are much larger<br />
and do not stay suspended indefinitely.<br />
Heterogeneous because at least two substances can be clearly identified.<br />
Connection: Some awful tasting medicines are suspensions, and are relatively thicker than<br />
other medicines.<br />
Colloids<br />
Colloid: A mixture whose particles are intermediate in size between those of a suspension and a<br />
solution<br />
Tyndall Effect: Scattering of light by particles in a colloid or suspension, which causes a beam of light<br />
to become visible<br />
Brownian Motion: The chaotic movement of colloidal particles, caused by collision with the particles of<br />
the solvent in which they are dispersed<br />
Emulsion: The colloidal dispersion of one liquid in another<br />
Particles in a colloid are spread out through the medium in which they are contained.<br />
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