Definitions Suck- Your Guide To Basic Concepts and Terms in Chemistry

*WARNING*: The following post requires reading *gasp*.

Pro Tip #1: Learn to love it. If you’re studying a subject and you really need, or really want to know it. Then you better start to like reading. I mean that literally, tell yourself that you love reading, right now. Do it every time you get sick of reading said subject. Better yet, tell yourself that you love the subject, it’s a cute puppy that you just got and you can’t stop cuddling it. You have to trick your mind in to believing that you are having fun, pretty soon, you will be.

Some professors out there never make you memorize a single definition, while others make you remember every god awful thing about a textbook. Naturally there is always a question about how many definitions you actually have to know.

Any good chemistry professor out there will never test you on a definition, because it is only important in so far as it helps you to understand a problem. Let’s take a look at the most basic definition in chemistry.

Matter– anything that has a volume and mass. (not to be confused with weight, which is how the mass and volume interact with gravity)


If that word ever comes up on any chemistry test, it’s probably time for a new professor. Remembering the word in and of itself is useless except in the bigger context. Chemistry IS the study of matter and it’s properties, so if you don’t know the definition of matter, then you don’t know what you’re studying.

Another word that chemists like to throw around is Composition (the stuff that makes up the matter). For example take the water inside of a glass. The water is matter, it is a Substance that is “composed” of water molecules (which are also considered matter but on a smaller scale). If you compare that glass of water to the water in the ocean you will find that even though both of those substances are considered water, they are composed of different things, which brings us to properties.


Properties are the things that make a substance unique. Like the element gold (Au) vs sodium (Na), or a violinist vs a serial killer, both are representative of the same class of thing (elements and humans) but are defined by their uniqueness.  Think of the properties that make you, you. You have eye color, hair color, facial features, a personality etc. Chemists use this uniqueness to identify substances.

Properties are further subdivided in to Physical properties (the things that a substance inherently has without interacting with other substances) and Chemical properties (how a substance interacts with other substances).

Pro Tip #2: Visualize. This is a handy trick to keep in your playbook for anything you do. The trick is to expand the visualization. A basketball player will see himself making a shot, but he also sees himself taking the shot. He thinks about how the ball will feel in his hands, how his arm is positioned etc. Over time this visualization helps to reinforce the neural circuitry in your mind. When you’re reading definitions try seeing the definition in your mind’s eye. For example, for “matter” I picture a glass measuring cup. The lines on the cup signify volume and the thickness of the glass reminds me of mass. Try it. Pick the glass up, turn it in your hands, feel the bumps that the painted lines make.

Physical changes are changes to the physical composition of a substance itself with no chemical change. The simplest physical change to think about is water (H2O). Whether it’s liquid water, Ice, or vaporized water the chemical composition stays the same. It will always be H2O.

Now lets talk Chemical changes which are reactions that turn a substance into a completely different substance. If you drop an acid like vinegar (acetic acid-CH3COOH) in to water (H2O) you make hydronium (H3O+) and an acetate ion (CH3COO-). This isn’t exactly relatable yet, but you’ll see what I mean later, the structures of those molecules have changed and as a result, so has their reactivity.

dropping acid

States of Matter

Really quick I want to touch on The States of Matter. These are Solid, liquid, and gas. It seems simple since we encounter it in everyday life but the definitions of these are also important when we’re talking chemistry.

Solids are substances that don’t conform to a container. Think of a grain of salt, it doesn’t It will remain a grain of salt in the container, it doesn’t flatten out on the bottom of the container to conform to it.

Liquid on the other hand conforms to a container but it doesn’t fill the container randomly. A cup of water doesn’t have a glob of water sitting at the top and the rest sitting on the bottom. I mean a small amount might stick to the sides, but we’ll get to that.

Gas fills a container AND conforms to it. If you spray a perfume in a room, the molecules will disperse throughout the entire room, until eventually they are distributed equally throughout the room.

Matter has a few characteristics that are shared by elements across the board. Everything has a melting point, freezing point, density, and vaporizing point (the point at which a substance turns to a gas. These rely on temperature and pressure to achieve a particular state and these can be reversed. Take water, it freezes at 0°C and 1 atm (atmosphere), take that temperature up just a little bit and it becomes liquid again, take it down and well you get the point.

Start to picture things. If you vaporize water at 105°C and 1 atmosphere in a sealed container and you want to convert it to liquid again without changing the temperature, what would you have to do? The water molecules are far apart, do you think increasing the pressure in the container will turn it to liquid again? Why do you think that is?

Chemistry has a unifying theme

It will be fun they said.jpeg

Chemistry, like all other sciences has a theme. It boils down to, those things which you see around you (macroscopic), from the chair you’re sitting on to that cute somebody you’ve been eyeing. These macroscopic materials are the result of millions of things happening on a microscopic level! To give you an idea of the implications of this statement, all around us there are an infinite number of atoms all interacting with each other to form the things that we are familiar with. There are electrons that are spinning around the nucleus of an atom all of the time! This means that the pot that is holding your houseplant is in constant motion! This effect is amplified when you realize that photons of light actually hit objects with a certain degree of force, so when you see an object, you aren’t actually seeing the exact location of the object because the force of the light is moving the object on a microscopic level!

Drained Yet? Well Here’s Some Energy For You

There’s probably no concept more important in chemistry, than that of ENERGY!!!! It is defined as the ability to do work. All it means is that movement occurs or has the potential to occur.

it's getting hot in here

Maybe you’ve heard of Potential Energy, It’s what happens when you drive to the top of a hill. The whole time you’re driving to the top you’re increasing the potential energy of your car (energy goes in and it increases according to the position of your car). You reach the top and you let your car coast down the hill, this puts turns the potential energy in to Kinetic Energy (The energy of motion). Remember Nature prefers states of lower energy, that’s why your car will coast down the hill until it reaches the bottom of the hill.

car potential energy.png

Well, that’s it, some basic concepts to get you started on your journey to becoming a scientists or whatever. I hope this helped, and as always, if you have any questions, comments or concerns, feel free to contact me via the contact page. Till next time.


[chemistry 211 section 1.1]

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