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Coffee is an important part of daily life for many people, with the average U.S citizen consuming 88.8 gallons yearly. You might wonder what you are drinking in your daily brew. For instance, we know coffee is a liquid, but what kind?
Coffee is a solution, not a compound or mixture, as it includes a solute that dissolves into a solvent. Compounds must be bonded chemically, and mixtures have visibly separate parts. Coffee can also be considered a mixture since it involves two mixed substances, but this is too vague.
This article will explain the differences between physical and chemical changes. That will help when I go into more depth about the difference between mixtures, compounds, and solutions. I will show why coffee is a solution and consider whether this is always the case.
Why Is Coffee a Solution?
To explain the differences between these terms, physical and chemical changes need to be discussed.
Physical Changes alter the state of something but not the type of molecules in it. A good example would be dry ice or liquid nitrogen. When below freezing, it is liquid, but at room temperature, it evaporates into a gas. It is still nitrogen, just in a different form. So physical changes are things like evaporating or freezing.
On the other hand, chemical changes involve a chemical reaction that alters the makeup of a substance. A famous example would be when hydrogen and oxygen combine to make water. The two types of molecules bond together to create a new substance that was not present before the reaction took place.
For more on this topic, here is a fun video to watch:
What Is a Mixture?
A mixture occurs when two or more substances are combined physically, not chemically. This could be as simple as putting milk with your cereal or adding oil to water. The two substances remain visibly separate despite occupying the same container. Any random sample of the mixture would likely have a different ratio of substance A to Substance B.They can also be taken apart relatively easily.
There are two kinds of mixture. These are Homogenous and Heterogenous, which I will now explain in more detail.
- Heterogeneous Mixtures – As mentioned, Heterogeneous Mixtures above do not have the same ratio of substance A to substance B in any given sample. This means they can only be a mixture.
- Homogeneous Mixtures – Homogeneous Mixtures, however, tend to have the same ratio of Substance A to Substance B throughout. All this means is that the substances are more closely mixed. However, this kind of mixture can sometimes be a solution depending on certain factors I will cover soon. This is why coffee can be both mixture and solution even if one is more accurate.
Here is a video with more examples of Homogenous and Heterogeneous Mixtures.
What Is a Compound?
Before I explain what a solution is, I need to explain why Coffee is not a compound. Unlike a mixture or a solution, a compound cannot be achieved physically. It can only happen through a chemical process. This means that a chemical reaction has to take place so that a new substance can form. You also can only separate the two or more types of molecules using chemical methods.
When you add water to the coffee, whether instant or ground, they mix and don’t bond chemically, and therefore, coffee is not a compound.
What Is a Solution?
Solutions are similar to mixtures in that they only need to be combined physically. However, a solution is always Homogeneous.
A solution also requires two things. These are:
- Solute – The ingredient that is dissolved.
- Solvent – The ingredient that does the dissolving.
An example of a solution left after this process is salt water, where the salt has been dissolved in water.
So for coffee, the coffee powder is the solute, and the water is the solvent. This is why a mixture is not specific enough to describe what coffee is while a solution describes it perfectly. As Peter Borrows writes in his article on Colloid Chemistry at the coffee shop, “If you dilute coffee ‘it will be apparent that this is a genuine solution, it is clear, not cloudy.”
Is Coffee Always a Solution?
Coffee is not always a solution as it is not always available in a way that properly dissolves in boiling water. What is Coffee?
Coffee is a beverage made from berries harvested from species of Coffea plants, native to South America, Asia, The Caribbean, and Africa. These berries are collected then roasted. After this, they may be ground.
For instant coffee, a slightly different process is necessary. Instant coffee is coffee extract, which is usually freeze-dried. Instant Coffee is also the most likely type of coffee to be classed as a solution but more later.
Does the Type of Coffee Matter?
Usually, coffee is available in several different forms.
The most common are:
- Ground Coffee
- Instant Coffee
Of course, beans cannot simply be added to water to make coffee. That would make a rough, useless mixture. To prevent yourself from resorting to this, if you accidentally buy beans instead of ground coffee for your machine, why not consider purchasing your very own coffee grinder.
The Hamilton Beach Fresh Grind boasts a removable grinding chamber, stainless steel blades, and is noticeably quieter than other models. With this product, you can grind fresh beans in the comfort of your own home.
Now, ground coffee essentially has to have hot water soak through the small pieces of coffee bean before being separated from the final product. For more detail on how this works, check out this video.
A good example of a coffee maker using this method is the Black+Decker 5-Cup Coffeemaker. This model is compact, with an ergonomic handle and permanent grounds filter. Its sneak-a-cup feature allows you to pour your first brew of the day before the rest has even finished brewing.
So, only instant coffee creates a true solution with the freeze-dried and treated coffee mixture dissolving into the hot water. One of the most flavorsome and expensive-tasting I’ve tried is Kenco Millicano Americano. Why not see the solute dissolve instantly with this tasty brand?
Does Adding Milk or Sugar Change It?
Adding milk and sugar does not change it. Milk and sugar dissolve along with the coffee, leaving a solution that has the same makeup throughout. However, the coffee would need to be stirred well and mixed in the right order to ensure that the solutes are properly dissolved.
Coffee can be both a mixture and solution:
- It is a mixture at any point, but more specifically, when the makeup is uneven, and the coffee is ground.
- It is a solution only when it is properly dissolved in the water and has the same balance.
Coffee is never a compound because it is made using a physical change, not a chemical one. The type of coffee can change which of these it is but adding milk and sugar won’t.