Glossary
Concentration of the Solvent
The amount of solvent present in a solution, which directly impacts the total amount of solute that can potentially dissolve.
Example:
Increasing the concentration of the solvent (e.g., adding more water) allows more solute to dissolve, assuming the solution was not already saturated.
Henry's Law
A law stating that the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the liquid at a constant temperature.
Example:
The fizz in a soda can is due to dissolved carbon dioxide, and when you open the can, the pressure decreases, causing the gas to escape, illustrating Henry's Law.
Homogeneous mixture
A mixture in which the components are uniformly distributed throughout, appearing as a single phase. Solutions are a type of homogeneous mixture.
Example:
Saltwater is a homogeneous mixture because the salt ions are evenly dispersed throughout the water, making it impossible to distinguish the salt from the water by sight.
Intermolecular forces (IMFs)
Attractive forces that exist between molecules, influencing physical properties like boiling points, melting points, and solubility. 'Like dissolves like' is based on similar IMFs.
Example:
The strong hydrogen bonding intermolecular forces (IMFs) between water molecules and ethanol molecules explain why alcohol is miscible with water.
Non-polar solutes
Substances with an even distribution of electron density, lacking significant partial charges, which allows them to dissolve in non-polar solvents.
Example:
Oil is a non-polar solute that does not mix with water but will readily dissolve in other non-polar substances like hexane.
Non-polar solvents
Solvents composed of molecules with an even distribution of electron density, lacking significant partial charges, making them effective at dissolving non-polar solutes.
Example:
Hexane is a common non-polar solvent used to dissolve greases and oils, as it lacks the partial charges needed to interact with polar substances.
Polar solutes
Substances with uneven distribution of electron density, creating partial positive and negative charges, which allows them to dissolve in polar solvents.
Example:
Table sugar (sucrose) is a polar solute that readily dissolves in water due to its many hydroxyl (-OH) groups forming hydrogen bonds.
Polar solvents
Solvents composed of molecules with uneven electron distribution, resulting in partial positive and negative charges, making them effective at dissolving polar solutes.
Example:
Water is a classic example of a polar solvent, capable of dissolving ionic compounds and other polar molecules like ethanol.
Saturated Solution
A solution that contains the maximum amount of dissolved solute at a specific temperature and pressure, with any additional solute added typically remaining undissolved.
Example:
A glass of sweet tea with undissolved sugar crystals at the bottom is a saturated solution, as no more sugar can dissolve at that temperature.
Saturation point
The specific concentration at which a solvent has dissolved the maximum amount of solute possible at a given temperature and pressure.
Example:
When you add sugar to water until no more will dissolve, you have reached the saturation point, and any additional sugar will simply settle at the bottom.
Solubility
The maximum amount of a substance (solute) that can dissolve in a given amount of solvent at a specific temperature to form a homogeneous solution.
Example:
The solubility of sugar in hot tea is much higher than in iced tea, allowing you to dissolve more sugar without it settling at the bottom.
Solubility Curves
Graphs that illustrate how the solubility of a substance, typically a solid, changes with temperature, showing the maximum amount of solute that can dissolve at various temperatures.
Example:
A chemist might use solubility curves to determine the optimal temperature for recrystallizing a compound, ensuring maximum yield.
Solubility Rules
A set of guidelines used to predict whether an ionic compound will dissolve in water, based on the identity of its constituent ions.
Example:
According to the solubility rules, most compounds containing nitrate ions (NO₃⁻) are soluble, which is why KNO₃ dissolves easily in water.
Solute
The substance that is dissolved in a solvent to form a solution. It is typically present in a smaller amount than the solvent.
Example:
When making lemonade, the sugar and lemon juice concentrate are the solute particles that dissolve in the water.
Solvent
The substance that dissolves the solute to form a solution. It is typically present in the largest amount.
Example:
Water is often called the universal solvent because it can dissolve a wide variety of substances, from salts to sugars.
Supersaturated Solution
An unstable solution that contains more dissolved solute than a saturated solution at the same temperature, often formed by carefully cooling a saturated solution.
Example:
Rock candy is often made by allowing a supersaturated solution of sugar to slowly cool, causing excess sugar to crystallize onto a string.
Surface Area
The total area of the exposed surface of a solute, which affects the rate at which it dissolves; smaller particles (larger surface area) dissolve faster.
Example:
Granulated sugar dissolves much faster than a sugar cube in water because its larger surface area allows more water molecules to interact with it simultaneously.
Undersaturated Solution
A solution that contains less than the maximum amount of dissolved solute at a given temperature and pressure, meaning more solute could still be dissolved.
Example:
If you add a small pinch of salt to a large glass of water, it forms an undersaturated solution because the water could dissolve much more salt.