Where are all the scientists in the building?
So, you probably may have come across the terms ‘’pure substances” and “impure substances” in various textbooks or notes, or they have been referenced by many people, and you are just there wondering, “What is the difference between a pure substance and an impure substance?”
If you are reading this article, sit back, relax and enjoy the ride you are about to embark on.
So, imagine you are holding a glass of water. This water has all the qualities that good water should have; it’s tasteless, colorless, odorless, and is probably boiled because you do not take water in an otherwise condition. In the lay sense, we can describe that water as pure, because it only consists of only one substance, water!
After a while, you drop the cup and decide to step out for some time, forgetting you have little kids in the house that always play, run around in the house, and generally drive you crazy. They move close to it thinking that it’s their play toy and decide to throw sand into your water. You majestically walk into the house and go straight to your water, only to find out that it has been contaminated!
Is that water still pure?
Now you may be asking, “What is the point of this analogy anyway? What is the difference between a pure and an impure substance?”
This is simply to explain that a pure substance is made up of only one substance. No substance comes in, no substance is withdrawn. In other words, pure substances are not mixtures.
Examples of pure substances are elements and compounds. An element is a chemical substance that cannot be divided into smaller substances or changed into another substance by ordinary chemical processes, while a compound is a chemical substance that is created when two or more different elements come together in a fixed ratio.
Now you may be thinking. “Isn’t it supposed to be only one substance? Why are compounds containing two or more elements called pure substances?” The reason why it is so is that pure substances, in chemistry, are definite matter that has unique chemical properties, and its composition is constant.
On the other hand, impure substances are substances that consist of two or more substances. Another way of defining impure substances is that they must not be a heterogeneous mixture. That is to say, if you can see the visible distinction between the compositions of the individual materials, the substance is impure. Case closed!
Examples of pure substances include gold, water, diamond, table salt, ethanol, brass, bronze, etc.
Examples of impure substances include shoes, sandwiches, light bulbs, oranges, wheat, etc.So, when this question pops up in your mind: “What is the difference between a pure and an impure substance?” remember that a pure substance contains only one material. It is free from any contaminant whatsoever. Examples include elements, compounds, and alloys with a fixed molecular composition. Impure substances contain two or more materials. They may contain contaminants.