On a rather wet and dreary day in the castle, Professor von Graft was sitting at her desk, sipping an obnoxiously large cup of coffee. She was glancing at some clippings from the Daily Prophet she had strewn about her desk. The enchanted copper moose was curled up and sleeping on a stack of essays waiting to be passed out from last week. Once the whole class has taken their seats, she slid the clippings in a drawer and looked up, smiling at her class.

Welcome everyone to the second week of Potions 101! I have enjoyed reading all of your introduction essays and I am overjoyed that so many of you are aspiring to be exceptional potioneers. I know that you are all anxious to brew your first potion, but I want you to be familiar with the fundamentals before setting you before the cauldron. This week, we will cover some simple chemical concepts and vocabulary, and next week we will discuss tools used in potion making and brewing methodology. Then you will finally be invited to brew the Cure for Boils in week four! I promise that we will not delve too deeply into the theoretical this year, but I do want you to have some simple background on what happens when your potions are brewing.

What You Say?
As we discussed in the last lesson, a potion is a magical mixture composed of magical, mundane, and transitional ingredients. We will cover what a “transitional ingredient” is later in this course. Individually, each of these ingredients have their own effects that either help or hinder the human body. However, when we place these ingredients in a cauldron and add both thermal and magical energy, it prompts those ingredients to restructure themselves, to state it simply, and to form new chemicals and compounds.

So let us delve into some of the terms defined above. A mixture is when there are multiple substances which are mixed together with no reaction taking place. To speak technically, this means that the molecules have not changed in character, and all of the materials involved in the mixture coexist with one another.

A mixture can either be considered heterogeneous or homogeneous. A mixture is considered heterogeneous when there is not one uniform substance throughout, but rather many different components combined together. You can pull apart and identify each of the materials in a mixture. A simple mundane example of this would be trail mix: while one purchases trail mix in one canister, it can be pulled apart and separated. If you only wish to consume peanuts, you can pick them out of this mixture; if you hate raisins, you can simply pick those out of the container. A mixture is considered homogeneous when you cannot visibly see the parts of the mixture but they are still able to be pulled apart without a chemical change. For instance, a salt water solution would be considered a homogeneous mixture. It appears to be one thing, but if you boil the water and evaporate it out, you’ll be left with the salt in the cauldron!

In contrast, a compound is a substance that occurs as a result of a chemical reaction of some sort between different substances. A compound can only be separated once again into its individual parts through another chemical reaction. For example, take the compound known as water. You will not have to know the chemical equation for this compound until the latter half of Potions 201, but for the sake of an example, you cannot separate out the individual substances that create water. However, you will learn that water is composed of a uniform collection of molecules consisting of the substances hydrogen and oxygen.

A pure compound is known as a homogeneous substance, or rather it has only one discernible ingredient throughout. To continue with the example of water, if you have a bucket of water, you can scoop out a cup, a liter, even a tablespoon of water. However, you cannot simply pull oxygen or hydrogen out of that bucket without a chemical reaction taking place; instead, you can only remove water.

Now, I often say that a potion is a mixture of compounds. This sounds confusing, but is really quite simple. Consider you’re making a red wine vinaigrette with oil, red wine vinegar, garlic, and a touch of mustard. These are all ingredients that are composed of different compounds themselves. You add all of these separate entities to a bottle and shake them up very well. All of them appear to mix into a single substance. However, there has been no change, and that dressing is still composed of these different ingredients: oil, vinegar, mustard, and garlic. You may even see the chunks of garlic and clumps of mustard floating in the dressing.

However, the individual parts of this dressing can still be separated again. Leave your salad dressing (after using a bit on your salad, of course!) for a day or so, then come back and look at the mixture. The different parts will likely have separated, heavier parts floating to the bottom. If you wish to use it on your salad again, you will have to shake it once more, mixing the ingredients so that they are make the nice, uniform, tangy salad topping. Potions typically don’t separate quite as obviously, but you can still often see evidence that they are a mixture of separate compounds. Say, for example, you see a ribbon of gold running through a teal potion. This likely indicates differing compounds. There may even be small elements of two or more compounds mixed in one uniform-seeming color.

This brings us to the topic of a solution, which is a type of a mixture. A solution is when there is a smaller amount of a substance, known as the solute, spreads throughout a greater quantity of another substance, known as the solvent. The solute (or solutes) does not have to be interspersed evenly throughout the solvent, but it does have to be there in some amount. One example of this is salt water. If you add a tablespoon of salt to a 350 ml (about 12 oz) cup of water, then stir it well, you will find yourself with a salt water solution. The salt -- the solute -- is spread throughout the water, the solvent. However, one can still distinguish the separate elements of saltwater: the salt crystals may even still crunch a bit if you bite down after a sip of the water.

Another good example of a solution is our atmosphere, which is composed of many chemicals and elements. Our atmosphere also shows that solutions do not only have to be liquids- they can be gases as well. This leads us into our next discussion of phases and phase transitions. This is something with which you should already be familiar from your daily life, even if you don’t know the name for the phenomena.

I will not go into detail on the mundane physics, but to boil it down, so to speak: solids, liquids, and gases are composed of basic units known as atoms and molecules (groupings of two or more atoms). If these particles are packed closely together and moving slowly, this is a solid. If they are packed less closely and experience slightly more dynamic (changing or active) movement, we see it as a liquid. You can move your hand through liquid because the particles are less closely-packed together. Gases have the least densely-packed particles of the three, and those particles have very active movement. The molecules and atoms are so loosely packed that you typically cannot see them. There is one more substance often called the fourth state of matter, known as plasma.Simply concentrate on the first three phases for the class and you will be adequately prepared to pass any examinations.

A phase transition is the term for when one of these phases passes through to another. This happens through a shift in energy, typically shown through a gain or loss of heat, which is the tangible evidence of thermal energy. For example, if you put an ice cube on a hot stove, you will see it melt and transition to water quite rapidly. In cases of extreme heat, you may even occasionally see it sublime, which is when the change in energy is so drastic, a solid transitions directly to a gas. Now this may be counter-intuitive for some, as I know that when I’m overheated, the last thing I want to do is move rapidly. However, if you think of heat as an expression of energy, the hotter something is, the more energy it is producing.

You are free to explore the mundane science of thermodynamics and other physics on your own, if you wish, and I will always encourage the curious to do outside research for enjoyment. However, for the sake of this discussion, we will merely concentrate on heat - or lack of heat - as how we perceive the energy that changes the activity of particles and causes substances to transition between phases. Be advised that there are other ways this energy can be created, however, including magic.

How does this relate to potions? Well, many ingredients maintain their solid form, but are simply dissolved into such small pieces that they cannot be individually distinguished within the potion. However, whenever you see the gentle billow of steam rising, this is indicating some sort of gaseous phase transition. Both the heat of your cauldron and the magic from your wand cause the change in energy that provides the catalyst for this reaction. The magic from your wand also leads to more complex chemical reactions, but we’ll cover that more later.

You will likely know most of these terms already, but here are the most common types of phase transitions:
Transition Name: Melting, Sublimation, Freezing, Evaporation/Boiling, Deposition, Condensation
Initial Name: Solid, Solid, Liquid, Liquid, Gas, Gas
Final Name: Liquid, Gas, Solid, Gas, Solid, Liquid

The Dust Has Only Just Begun to Fall (The Briefest of Looks at Theory)
If you are like me, when you see something you don’t quite understand operating, your first thought is “How does that work?” My next is usually “What happens if I poke it just a little bit?” I advise you don’t ask the second question until you have just a little more understanding of potions and the theory behind mixing ingredients. However, you may still be asking yourself what makes a potion work.

Well, the different components combining do not simply react on their own. If you threw the ingredients for the Cure for Boils - which you will brew in lab later this year - into an empty cauldron and just left it sitting there, it would be no closer to forming a Cure for Boils than when the ingredients were sitting separately. In later years, we will discuss certain combinations of ingredients that were once used without a brewing process, but these were not true potions. Instead, they were combinations of ingredients, each of which achieved a certain related effect. However, in brewing true potions, it requires the energy of heat as well as the magic in your wand in order to initiate a reaction in the ingredients. The order you add the ingredients becomes important, because it enables certain ingredients to react in a specific way as the potion is brewed. This reaction causes the bonds of molecules, as mentioned briefly above, to create something brand new. If this sounds confusing, we will cover the science of this later, so fear not!

Truthfully, a good deal of information about potions theory and how ingredients interact with magic is still a mystery. You may never become a researcher or have interest in advanced theories of potions, but in this class, I hope to at least instill the importance of understanding the fundamental theory behind something: with this understanding, we are able to manipulate, innovate, and make new and exciting discoveries. In the past, magical technology has often stagnated because more conservative minds were content with continuing to use tried and true methodology without thinking to investigate how it worked, and what other potential it held for magical innovation and advancement. The tide is slowly turning, but there is still a good deal of pushback against what is deemed an “odd” and occasionally “laughable” group of researchers.

And with that, I will leave you for today. Good luck on your quiz and, if you choose to do it, your extra credit essay! I will see you next week when we discuss potions equipment and technique.