No, coffee is not a pure substance.
In the article that follows, we’ll explain what the qualifications are to be considered a pure substance. Then, we’ll examine why it is that coffee does not qualify, both in the prepared form and also in the bean/ground coffee form.
Why Isn’t Coffee a Pure Substance?
The first step to this answer is to understand what a pure substance is and is not.
A pure substance is any substance which is made up of just one kind of building block.
That building block could be an element (which is a material that is broken down into the simplest form that exists), or it could be a compound (a molecule that is made when two or more elements chemically bond to each other).
In any case, there are no other types of atoms, elements, molecules, or compounds in the material.
Is Brewed Coffee a Pure Substance?
No, brewed coffee is not a pure substance. Brewed coffee is made when hot water is poured over ground up coffee beans, and allowed to steep for a short or longer period of time.
The water drips out of the ground eventually, bringing along with it the components of of the coffee beans which dissolved into the water. There is also generally a small amount of particulate bean that sneaks through as well.
Brewed coffee is not a pure substance because the brew contains water (which is hydrogen bonded to oxygen), and it contains the dissolved coffee bean materials (oils, chemicals, and more).
Since there is more than one building block that goes into the composition of brewed coffee (water and coffee), then brewed coffee is not a pure substance.
Are Coffee Grounds a Pure Substance?
No, coffee grounds (or even coffee in the bean form) are not a pure substance.
While ground up coffee might look like it is just coffee, for the purposes of determining whether a substance is pure or not, we look as deep as the molecular level (and perhaps beyond).
While ground coffee might seem like a simple substance, it is not.
Coffee is actually made up of multiple components, such as proteins, oil, caffeine, tannins, carbohydrates, and more. (source) The chemical compositions of these various components differ greatly.
As a result, because there are multiple building blocks that make up ground coffee (even when it is not mixed with water), ground coffee (or whole coffee beans) cannot be a pure substance.
Remember, coffee beans come from plants.
They are grown. Think about all the various structures, liquids, and chemicals that are part of a growing plant. When you think of coffee that way, it makes the questions of whether coffee is a pure substance or not much easier.
Is Black Coffee A Pure Substance?
No, black coffee is not a pure substance. As discussed above, coffee is composed of many different types of substances and chemicals. When you prepare black coffee, you also add water as a component of coffee.
Since a pure substance is a material that is made up of only one kind of building block (like an element or one compound), black coffee (made with water and coffee) is not a pure substance.
Is Instant Coffee A Pure Substance?
No, instant coffee is not a pure substance.
Instant coffee can be made many ways, but generally it comes from dried coffee extract. The coffee is brewed, and then the water is removed, leaving behind a substance that can again be dissolved in hot water.
Since instant coffee usually comes from coffee beans (though brewed and then water removed), it still contains many of the material that disqualified coffee (brewed, ground, and black) from being considered a pure substance.
Instant coffee (like regular coffee) still contains oils, caffeine, and many other chemicals.
Not to mention as soon as you put the instant coffee into water to get it ready to drink, you’ve added another substance.
If Coffee Is Not A Pure Substance, What Are Some Examples Of Materials and Substances That Are Pure Substances?
As we said, a pure substance can be made up of elements, or of compounds.
The most obvious pure substances are elemental materials, such as gold, iron, zinc, lead, copper, sulfur, diamond, and tin.
There are many pure substances which are made up of compounds, such as distilled water, carbon dioxide, salt, sugar, and baking soda.
Un-distilled water is considered a pure substance, but it is rarely found on Earth without some sort of impurities. (Read Is Water a Pure Substance?)
On the same topic, you might be interested to learn:
To learn more about rocks, minerals, and how our world works, check out our knowledge hub for our latest articles.