Is tap water homogeneous or heterogeneous

My contribution to the Internet -

Actually, the headline says it all - you think. There are pure substances and there are mixtures, i.e. several substances mixed. But it's not that simple after all.

Basic substances

Basic substances are substances that only consist of one type of tiny particle. If that were the case, there would be no pure substances and probably one will never be able to produce such a pure substance in large quantities. In fact, a basic substance mainly consists of just one substance. But what is called "pure" depends on the requirements. Tap water is fairly pure but contains some minerals that are seen as "water stains" when water droplets dry. Even so, tap water is pretty pure. A purity of around 95% is often sufficient to speak of a pure substance, sometimes 99.999% purity is still too low.

A pure substance is actually a mixture, but it mainly consists of one substance. The impurities are so insignificant that they do not play a role in the current application. If this is the case, one speaks of a pure substance.


A mixture is actually a mixture of several substances. One substance can be dominant here, but the other substances in the mixture influence the properties of the mixture so much that they cannot be neglected. If this is the case, an speaks of a mixture or a mixture.

The properties of a mixture depend on the type of substances mixed and the mixing ratio.

In order to change the properties of a mixture in a targeted manner, one can change the substances involved and / or vary the mixing ratio. Both will lead to changed properties of the mixture. Everyone knows this from cooking, for example. If you add more sugar to the pudding, the taste becomes sweeter. If you take honey instead, you also get a sweetener, but there are also other flavor components from the honey.

materialproportion of
nitrogen78.1 vol%
oxygen20.9 vol%
argon0.9 vol%
Carbon dioxide0.038 vol%
other trace gasesthe rest

Since the number of substances is almost unlimited, this naturally also applies to the mixtures. There is an incredible variety. Most of the substances we deal with on a daily basis are actually mixtures. For example, air is a mixture that mainly consists of nitrogen and oxygen. Schnapps is a mixture of water and alcohol and some other substances in very small proportions. Petrol is a mixture of a relatively large number of substances. Except for salt and sugar, most "foods" are mixtures.

If you compare these few examples alone, you will notice some significant differences: air is gaseous and liquor is liquid, but both have in common that you cannot tell that they are a mixture. Wholemeal bread is clearly firm for everyone and also clearly a mixture. If we take the pudding from above, we may not see with the naked eye, but at the latest with the microscope, that it is a mixture; firm but with individual gas bubbles in it. Because of this variety of mixtures, a distinction is made between numerous different types of mixtures.


Homogeneous mixtures

Homogeneous is derived from the Greek "homos" for equal and means something like "similar" or "uniform". A homogeneous mixture is a mixture that cannot be seen, even with the most powerful microscope in the world.

Homogeneous mixtures look like pure substances and can be solid, liquid or gaseous. Whether a homogeneous mixture can form depends on the force of attraction between the smallest particles of the substances involved. Let us assume that we mix substances A and B: In order for a homogeneous mixture to be formed, the forces of attraction between a particle A and a particle B must be able to develop so strong that they are comparable to those between A and A or B and B. . The reason for this is that particle A lies next to particle B in the homogeneous mixture and the particles are no longer "sorted". It must therefore be irrelevant for particles of type A as well as for those of type B which kind of particle is their neighbor. If the forces of attraction between A and A or B and B are much stronger than between A and B, a homogeneous mixture cannot form.

Gas mixture Since the forces of attraction between the particles of a gas are completely ineffective, gases actually always mix. In the gas mixture, all particles can move freely, regardless of the "type of particle". For example, air is a gas mixture. (so.)
solution Salt water or sugar water are solutions. Most solutions are liquid and consist of a solvent (e.g. water) and one or more dissolved substances (e.g. salt, sugar, ...). In the solution, the particles of the solute are surrounded by those of the solvent. The particles of the solute are said to be "solvated" or, if the solvent is water, also "aquotized". The most common substance in the mixture is usually referred to as the solvent.
alloy An alloy is a solid, metallic mixture. Examples are brass, bronze, amalgam, ... In most cases the alloy consists only of metals, only in a few examples are non-metals involved in the alloy. However, the alloy always shows typical properties of a metal such as gloss and electrical conductivity. Most alloys are solids. As in all homogeneous mixtures, there is also an even distribution of the particles of all substances involved in the alloy. Larger areas that only consist of particles of one type of particle do not occur.

Heterogeneous mixtures

Heterogeneous is derived from the Greek "heteros" for "different" and means something like "inconsistent". In heterogeneous mixtures, only weak or no forces of attraction can develop between particles A and B, which is why the particles of type A and / or type B "want to stay among themselves". Mixing the smallest particles is therefore not possible. Heterogeneous mixtures therefore actually consist of a mixture of pure substance particles. These "pure substance particles" can be solid, liquid or gaseous and the heterogeneous mixture is accordingly divided into according to the physical states of the substances involved.

mixture Two or more solids are mixed together. Examples are garden soil, a mixture of salt and sugar, rubbish ... How big the particles can be is not specified. Basically, for example, the contents of a wardrobe could also be called a "mixture".
suspension In a suspension, a solid is slurried (suspended) in a liquid, such as sand in water. Usually suspensions separate relatively quickly.
emulsion In the case of an emulsion, at least two actually immiscible liquids are mixed with one another. Probably the most prominent example are water / oil emulsions, such as those used in salad dressings. Emulsions also normally separate by themselves, but can be stabilized by adding an "emulsifier".
smoke In the case of smoke, small solid particles are distributed in a gas, such as dust in the air. With larger particles, the smoke separates relatively quickly because the particles sink to the ground. Only with very small particles and sufficient mixing is the mixture stable long enough to make it into the media as "fine dust", for example.
fog A mist contains small liquid droplets in a gas, as does the mist.
Aerosol An aerosol contains solid and liquid particles in one gas, i.e. a mixture of smoke and mist. Often the term is also used for "fog". The distinction between smoke, mist and aerosol is often not clear in the media.
foam In the case of a foam, gas bubbles are contained in a liquid or a solid. So foam is the bath foam or the foam from the sofa.

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