Coffee: A Mixture or a Substance?

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Coffee has become an essential part of the crucial morning routine. So you might be wondering, “what exactly am I putting in my body?” When looking at what coffee is made of, if it’s a pure substance or a mixture, how it can be mixed, etc. It gets interesting.

Some people think that coffee is an absolute pure substance while others believe that it’s a mixture. To answer this question, you have to first know what a substance or mixture is.

What’s a pure substance?

Do you remember science class in school? You probably saw something called the periodic table that lists elements like copper or zinc.

A pure substance is something that is made from one element or substance. Now, it’s important to understand that while elements are great examples of a pure substance, not all pure substances are elements.

If you’re confused, well it gets more confusing. Some people consider a homogenous mixture to be a pure substance as well. A homogenous mixture is a mixture where the mixture is uniform.

Examples of a pure substance

So now we know that pure substances can be elements, non-elements, and even homogenous mixtures. Here are some examples of what a pure substance is.

Let’s start with some no-brainers:

  • Diamond
  • Silicon chips
  • Baking soda
  • Gold metal
  • Caffeine

Here’s a short list of the gray area of pure substances, and homogenous mixtures:

  • Water
  • Honey
  • Stainless steel
  • Air
  • Sugar water

Homogeneous mixtures are viewed as substances because of their structure and nature. Now, if you’re confused, don’t worry. A good rule of thumb is that a homogeneous mixture can be used to make a separate mixture.

What’s a mixture?

Have you ever mixed water and flour to mix dough? Water and soap to make a lather? Well, you’ve made a mixture to create something else. That’s the whole point of a mixture. Sounds a bit like coffee, right?

Mixtures can be homogeneous or heterogeneous (dough is a good example) and is not a chemical compound. Mixtures can be split into their base substances through filtration or some other method. Mixtures also retain the properties of the substances used in the mix, unlike a compound.

Types of mixtures

There are a lot of examples for mixtures and some homogeneous ones were already listed under substances. Let’s look at some examples of heterogeneous mixtures and how they can be different.

  • Cereal and milk
  • Soda and ice
  • Blood
  • Pizza
  • Coffee (Can be homogenous or heterogenous)

As you can see, a heterogeneous mixture can be just about anything. It also makes a final mixture where its separate parts can be clearly seen (like the ice in soda and ice). It’s a bit more difficult to “see” the separate substances in a homogeneous mixture.

So what about coffee: Mixture or substance?

It’s been kind of spoiled already, but yes coffee is a homogeneous and heterogeneous mixture! If it’s black coffee, it’s homogeneous, when you add cream, sugar, and other things, then it turns into a heterogeneous mixture.

The caffeine in coffee, however, is a pure substance. Don’t get too confused by this because it makes perfect sense.

Caffeine can stand on its own while coffee has to be mixed to be used as a drink. Coffee is often brewed with water, mixed with creamer, or half and half, and the ratios vary a lot. In fact, each coffee drinker makes their coffee differently, some in very small ways.

Caffeine: The pure substance from coffee

Caffeine can be consumed from coffee or it can be taken in a pill or powder form. It can even be added to other mixtures to add a bit of kick to it. Like how caffeine is in soda, energy drinks, and even products like pre-workout powders.

You can’t add coffee itself to something like a pre-workout (well, you shouldn’t!) like with caffeine. Hopefully, this clears up the difference between coffee and caffeine and how one is a substance but the other is a mixture.

What coffee is not

Coffee is not a chemical compound. While this isn’t something that many people get wrong, it still happens. A chemical compound is a lot more difficult to create than a mixture. It’s not something that you’re just gonna whip up on a Monday morning.

Chemical compounds usually involve some form of energy (heat, electricity, etc) applied to a mixture. The final product also does not retain the original properties of the substances used in the chemical compound.

Wait, what about solutions?

You may have heard about some people calling coffee a solution, and they wouldn’t be wrong—completely. A solution is a mixture that happens when a solvent (hot water) turns a solute (coffee beans) into a homogeneous mixture (black coffee).

Coffee ceases to be a homogenous mixture when you start adding things to it, even ice cubes. Now, does it still remain a solution, sort of? The coffee solution has to come first before turning it into a heterogenous mixture, like an iced coffee or other coffee drink.

What is coffee made of?

Coffee is formed from caffeine, tannins, protein, and oils. All of these are released in different ways depending on how coffee is brewed.

For example, a cold brewed coffee will be less acidic than hot brewed coffee. The temperature affects how the properties react in the final mixture.

Summary

Coffee can be a bit confusing to understand when determining if it’s a mixture, substance, or something else. Pure substances stand on their own and include sugar, gold, elements, and homogeneous mixtures like water. A mixture is when two substances come together to form a new thing, like water and flour mixing to form dough.

What makes coffee confusing is that it can be a homogenous mixture derived from a solution and a heterogeneous mixture. When you make black coffee, it’s a homogenous mixture derived from a solution.

If you start adding things to coffee, like cream, ice, or sugar, that’s what makes it a heterogeneous solution. So go ahead and enjoy your daily morning mixture of happiness and start your day!