Alcohol is water a homogeneous mixture

Alcohol doesn't just solve problems ...

Experiment: alcohol as a solvent
Experiment: homologous series and solubility of alcohols

In general, the principle "like dissolves in like" applies. This means that substances that are similar in their structure and thus also in their polarity can be dissolved in the solvents. It's different with alcohol.

Ethanol as a solvent
Experiments show that ethanol can be mixed with both water and gasoline (-> experiment). This in itself is very unusual, because water and gasoline (almost!) Do not go together at all. So there has to be something special about the molecule of ethanol so that it is able to mix with two very different substances.

The two terms "hydrophilic" and "hydrophobic" are used to characterize the solution behavior of a substance towards water.

What do the terms "hydrophilic" and "hydrophobic" mean?
The words come from the Greek. Hydro stands for water, philos is called friend and fobos means fear, aversion.
So you can be hydrophilic with Loving water Translate. A hydrophilic substance is therefore very water-soluble. Substances that mix well with water are always polar (like water) or electrically charged.
The opposite of being hydrophilic hydrophobicwhat as much as Fearing water means. A substance is called hydrophobic if it is poorly or not at all soluble in water. These are always non-polar or electrically neutral molecules. E.g. fats, oils and alkanes are hydrophobic substances.

If a substance is fat-soluble, it is also known as lipophilic (Greek lipos = Fat).

The explanation for the solution behavior of ethanol
This provides us with its molecular structure. The solution behavior of this compound is determined by the different properties of the two parts of the molecule. For one thing, its molecule contains one Hydroxyl group (OH group), which is similar to the water molecule. Ethanol owes its ability to dissolve in water to this functional group. This is why this alcohol is also referred to as a hydrophilic (water-loving) substance.

But why is that? The bond between the hydrogen and oxygen atom is polar because the oxygen atom attracts the bonding electrons due to its high electronegativity and it now has a higher electron density. Thus there is a positive partial charge (δ+) on the hydrogen atom and a negative (δ-) on oxygen. So ethanol molecules are dipoles - like water molecules. Both molecules have the same polarity and are therefore soluble in one another.

Polarities of water and ethanol

In addition, both compounds can form hydrogen bonds with one another, which creates attractive forces between the molecules. This is another aspect that favors mixing. However, ethanol molecules can only form one bridge to their neighbor, whereas water molecules can form two.

On the other hand, the ethanol has one Alkyl group, a gasoline-like hydrocarbon residue. Between this remainder and gasoline there are Van der Waals forces; these are forces of attraction between non-polar molecules.
The hydrocarbons are therefore also hydrophobic (water-repellent). Thanks to the alkyl group, ethanol also dissolves non-polar substances, such as B. Fats.

Ethanol dissolves in gasoline and water

To some extent, ethanol can "combine" water and gasoline. In this way, even ternary mixtures are formed. A dehydration method for alcohols is based on this.

Ethanol therefore has both a hydrophilic and a lipophilic part, which explains its excellent dissolving behavior.

The longer the chains, the more hydrophobic / lipophilic the alcohol is
Only the first three alcohols are soluble in water in any mixing ratio (-> try). Butanol, for example, already shows a miscibility gap. This can be seen from the fact that two phases form when the two liquids are mixed: a water-rich phase (bottom) and a butanol-rich phase (top).
Long-chain alcohols in particular (fatty acid alcohols) are completely water-repellent. However, if you dissolve it in gasoline and pour it onto water, a fur-like layer of alcohol molecules forms on the surface of the water - the alcohol acts like a Surfactant. The OH group dips into the water, the lipophilic hydrocarbon chain points into the non-polar air (-> experiment).

Further texts on the subject of `` alcohol ''