Substances - LeFonch

A substance is a form of particles that can be group into more specific classes.
There are two main forms of substances, pure substances and mixtures.

Pure Substances

Pure substances are either raw elements or compounds of elements, such as carbon dioxide or water.
Compounds are made of two or more elements, bonded together.
Compounds can be ionic, such as NaCl, or covalent, like H₂0 for example.
Covalent compounds are always formed from non-metals, with a few exceptions such as silicon.
Ionic compounds are formed between metals and nonmetals.
Compounds can only be separated through chemical methods (chemical reactions).

Mixtures consist of two or more pure substances.
The ingredients of the mixture can be separated from each other by physical methods such as evaporation, filtration, or distillation.
Mixtures can be homogenous, meaning that it is full mixed and the different substances can't be differentiated.
The different substances in homogenous mixtures can't even be seen under microscopes, as you'd need to see the individual atoms to tell the difference apart.
For example salt dissolved in water.
Otherwise mixtures can be heterogenous, meaning that the substances can easily be differentiated.
For example sand in water.
Heterogenous mixtures can be often be separated with filters, whereas homogenous mixtures often require more elaborate methods to separate.
Miscibility is how easily a substance forms mixtures. A miscible substance can mix easily, whereas an immiscible substance usually won't form mixtures.
Although the phrase is commonly used for liquids, it can also be applicable to gases and solids.

A phase is a region of state in a mixture with precise boundaries.
The term phases can usually be used interchangeably with states of matter, however not that in some cases the same phases might be immiscible.
For example, how a solid and a liquid won't mix; it means they are in different phases (a liquid phase and a solid phase).
The same can apply for the same states of matter, such as the boundary between cooking oil and water.
When a substance is in one phase(meaning the mixture has fully mixed), it is homogenous.
For instance, milk is an example of a homogenous mixture, as you can't tell apart the different substances in a glass of milk.
In a homogenous liquid solution, the solute and solvent mix perfectly.
In a saturated solution, more solute cannot be dissolved by the solvent at the current temperature.

A suspension is a fluid which contains solid particles with a size of over 1 micrometer (or 1000 nanometers).
This means the solid particles are too large to float and eventually fall to the bottom of the container.
Thus suspensions aren't solutions, as both substances have distinct and easily noticeable phases.

The opposite of a suspension is a colloid.
In a colloid particles are smaller than 1 micrometer, and thus float in the liquid.
Although colloids may appear like a true solution, they are still heterogenous and thus not a true solution.

An emulsion is similar to a colloid, however the mixture only contains liquids.
It is when two liquids that normally don't mix are in a mixture (similar to the solid particles floating around in a colloid, but liquid).
Although emulsions, like colloids, might look homogenous on a macroscopic level, they can be differentiated on a microscopic level and thus not true solutions.