Is Soil a Pure Substance? [Explained]

is soil a pure substance

We all love gardening as a hobby but have you ever wanted to examine it on a more scientific level?

Soil is the foundation of our garden, so getting to know it on a deeper level will unlock its mysteries and take your gardening to a whole new level. So let’s take a look at its structure and ask ourselves; is soil a pure substance?

Soil is not a pure substance because it comprises multiple elements and compounds. For this reason, it is considered a mixture.

When you take a look at soil with the naked eye, ceratin kinds may appear like a pure substance, but when you look at it under a microscope, you will find that there is so much more hiding beyond our sight.

This article is going to explain what a pure substance is and break down whether or not soil classifies as one.

Grow Your Yard Fact
As well as being a mixture, soil is also heterogeneous. Find out why here.

What is a Pure Substance?

Before we can figure out whether soil is a pure substance, we need to update ourselves on some scientific terms.

So what exactly is a pure substance?

A pure substance contains only one type of matter and has fixed properties.

This includes singular elements as well as compounds. So both oxygen (O2) and water (H20) are both considered to be pure substances. The compounds are chemically bonded and cannot be physically separated.

Mixtures, on the other hand, are substances that have been combined where no chemical bond occurs.

Each component of the mixture will retain its original properties and can be physically separated. Mixtures can be either heterogeneous or homogeneous.

For example; salt water is a homogeneous mixture, while peppercorns and coarse salt is a heterogeneous mixture.

So, now that we have this all this info, we can figure out whether soil is a pure substance.

Is Soil a Pure Substance?

Soil is not a pure substance because it contains more than one type of matter in a heterogeneous mixture.

Rather than one element or compound, soil is a mixture that is made up of a variety of materials in differing quantities. It is created through a combination of physical, biological, and chemical weathering and forms the surface material of the Earth’s layers.

On top of that, the soil will change from location to location across the world, so the mixture itself will be very different. You can alter your soil mixture by adding soil amendments like coco coir, worm castings, lime, and vermiculite.

So what is soil a mixture of?

Soil is made up of a few different components:

Organic Matter

This mostly comprises of dead plant and animal matter that has decomposed to create a rich topsoil that provides a host of nutrients for your plants. You can increase the organic matter content in your soil by adding compost.


The mineral content in soil is predominanty a result of the breakdown of rocks over time.

Weathering is the main source of this breakdown, which can happen in many ways including contact with water, impact, and plant and animal activity.

The exactly mineral present and theri quantities depends on what rock is local to that area. You can adjust the minerals to improve the nutrients in your soil and regulate your soil pH through soil amendments.

Living organisms

Apart from dead organic matter, there is also living organic matter present in the soil in the form of insects and various microorganisms.

This includes worms, beetles, and larvae, which you can see with the naked eye. However, there are even more creatures hiding in the soil on a microscopic level like fungi and bacteria that are crucial for creating a healthy environment for plants and insects to thrive.


Even the densest clay soil will have some form of air in it. Air pockets commonly form between the particles of matter within the soil, especially when it consists of larger pieces of matter.

Loam and sand will contain more sir than silt and clay, due to their particle sizes.


All healthy soil requires a good water content to keep your plants nourished. The water content of soil will vary dramatically depending on the soil type; sand, silt, clay, or loam; and the climate of the region it is located.

Within the mixture that is soil there are elements that are in solid, gaseous, and liquid form.

Grow Your Yard Tip
Soil can be expensive! That’s why we like to reuse old soil; find out how here.

Frequently Asked Questions

Is soil a compound or a mixture?

Soil is a mixture, but what is the difference between a compound and a mixture?

As we discussed above, a mixture is a combination of ingredients that can be physically separated from one another. Compounds, on the other hand, are chemically bonded elements that can’t be physically separated from one another.

Is water a pure substance?

In its original form (H20), water is a pure substance as it is made up of chemically bonded elements of hydrogen and oxygen. However, most of the water on earth has some kind of contaminant or chemical treatment, making it impure.

What is a mixture of soil called?

The perfect blend of soil comes in the form of loam.

Loam is a type of soil made up of clay, silt, and sand. It has great water retention and good drainage, which makes it the ideal soil for many plants.


A complex substance, soil, is made up of many elements that can vary from place to place.

Soil is not a pure substance because it is a mixture that is made up of a variety of substances of different sizes rather than only containing a singular type of molecule.

We don’t know about you, but learning about soil like this really gets us itching to get into the garden with our new appreciation. Happy gardening!

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