Glossary
Boiling Point
The temperature at which a liquid changes into a gas (vaporizes) at a given pressure.
Example:
Water has a boiling point of 100°C at standard atmospheric pressure, which is why it boils at that temperature.
Chromatography
A versatile separation technique that separates compounds based on their differential interactions with a stationary phase and a mobile phase.
Example:
Forensic scientists use chromatography to separate and identify components in ink samples from a ransom note.
Column Chromatography
A chromatography technique where a mixture is passed through a column packed with a stationary phase, allowing for the separation and collection of larger sample sizes.
Example:
Researchers use column chromatography to purify proteins from a complex biological mixture in a lab.
Distillation
A separation technique used to separate liquids with different boiling points by heating the mixture, vaporizing the lower boiling point component, and then recondensing it.
Example:
To purify water by removing dissolved impurities, one might use distillation to collect the condensed water vapor.
Evaporation
A separation technique used to separate a soluble solid from a liquid by heating the solution until the solvent vaporizes, leaving the solid behind.
Example:
If you boil a pot of saltwater until all the water is gone, the salt left at the bottom is a result of evaporation.
Filtration
A separation technique that uses a porous barrier to separate an insoluble solid from a liquid, allowing the liquid to pass through while trapping the solid.
Example:
Making coffee involves filtration, where the liquid coffee passes through the filter, but the solid grounds remain.
Fractional Distillation
A more refined distillation method used to separate liquids with very close boiling points, involving multiple vaporization and condensation cycles within a fractionating column.
Example:
The petroleum industry uses fractional distillation to separate crude oil into different components like gasoline, diesel, and kerosene.
Insoluble Solid
A solid substance that does not dissolve in a particular liquid, forming a heterogeneous mixture.
Example:
Sand is an insoluble solid in water, which is why it settles at the bottom when mixed.
Intermolecular Forces (IMFs)
Attractive forces that exist between molecules, influencing physical properties like boiling points and solubility.
Example:
Water's high boiling point is due to strong hydrogen bonding, a type of intermolecular force.
Mobile Phase
In chromatography, the fluid (liquid or gas) that moves through the stationary phase, carrying the components of the mixture along with it.
Example:
The solvent that travels up the paper in paper chromatography is the mobile phase.
Non-polar Compounds
Molecules with an even distribution of electron density, lacking significant partial charges, and tending to interact strongly with other non-polar substances.
Example:
Oils and fats are non-polar compounds, which is why they don't mix well with water.
Paper Chromatography
A type of chromatography where a solvent moves up a strip of paper (stationary phase), separating compounds based on their differing affinities for the paper and the solvent.
Example:
Separating the different colored dyes in a black marker can be easily demonstrated using paper chromatography.
Polar Compounds
Molecules with an uneven distribution of electron density, resulting in partial positive and negative charges, which tend to interact strongly with other polar substances.
Example:
Water is a polar compound, which is why it can dissolve other polar substances like sugar.
Porous Barrier
A material with small holes or pores that allows liquids or gases to pass through while blocking larger solid particles.
Example:
Filter paper acts as a porous barrier in filtration, letting water through but stopping sand.
Rf Value
In chromatography, the retention factor, calculated as the distance traveled by the compound divided by the distance traveled by the solvent front, used to characterize and identify substances.
Example:
If a compound travels 3 cm and the solvent front travels 6 cm, its Rf value is 0.5, indicating its relative affinity for the stationary and mobile phases.
Silica Gel
A common polar adsorbent material used as the stationary phase in chromatography, particularly in TLC and column chromatography.
Example:
In TLC, compounds that are more polar will stick more strongly to the silica gel plate and travel a shorter distance.
Simple Distillation
A distillation method used when the boiling points of the liquids in a mixture are significantly different, involving a single vaporization and condensation step.
Example:
Separating water from a salt solution is typically done using simple distillation because their boiling points are very far apart.
Soluble Solid
A solid substance that can dissolve in a particular liquid, forming a homogeneous solution.
Example:
Table salt is a soluble solid in water, readily dissolving to form saltwater.
Solute
The substance that is dissolved in a solvent to form a solution, typically present in a smaller amount.
Example:
In a sugar water solution, the sugar is the solute that disperses evenly throughout the water.
Solution Separation Techniques
Methods used in chemistry to isolate components (solutes) from a mixture (solution) based on their differing physical properties.
Example:
When you need to get pure water from saltwater, you'd use a solution separation technique like distillation.
Solvent
The substance that dissolves a solute, forming a solution; it is typically present in the larger amount.
Example:
Water is often called the universal solvent because it can dissolve many different substances.
Stationary Phase
In chromatography, the immobile material (solid or liquid coated on a solid) that the mixture components interact with as the mobile phase moves through it.
Example:
In paper chromatography, the paper itself serves as the stationary phase that compounds adhere to.
Thin-Layer Chromatography (TLC)
A chromatography technique similar to paper chromatography but using a thin layer of adsorbent material (like silica gel) coated on a plate as the stationary phase.
Example:
Organic chemists often use Thin-Layer Chromatography (TLC) to quickly check the purity of a synthesized compound.