The Mole As A Unit

I’m currently sitting in a library at UC Berkeley, fresh out of my first office hours session!! Just so you know, I’m mentally patting myself on the back for attending office hours and asking a few of my own questions while also listening intently to what others were asking. Before I talk about the mole (the chemistry mole, that is), I want to quickly talk about how amazing office hours actually are.

I’ve been at Berkeley for a little less than a week now and not going to lie, it’s been tough. I’m not talking about school work or exams, though those will definitely become harder in the coming weeks; I’m talking more about adjusting to life without seeing my family everyday and getting used to my dorm situation, etc.

Office hours was the first school-related “event” that made me really excited to be at Berkeley, which I think says a lot.

Coming to office hours was a spur of the moment decision for me because right now I understand the chemistry lectures and the homework seems straightforward enough. I decided to go in and see my graduate student instructor (referred to as a GSI) just to get an idea of how to seek help later on when I will most likely need it. This was the best decision I’ve ever made. Even with my basic understanding of the material from lectures, the GSI contributed so so so much more to my thought process regarding chemistry. You could tell he was extremely well-versed in chemistry (I mean, duh, he’s a graduate student at Berkeley!), but more than that he was able to break down complex concepts into really manageable ideas. This is how I came to the idea of the mole, which wasn’t even a huge part of my lecture notes this week. So here we go!

The Mole 

In past chemistry classes, I have thought of the mole as many things: an amount, a useful conversion factor, etc. The one thing I have never thought of the mole as is what it actually is…A UNIT! This may seem really insignificant but conceptually it has helped me so much. The mole is a manmade unit!

My GSI compared the mole to a dozen which is simply another unit we use to describe how many there are of a certain object. I could have a dozen eggs for example, or I could even have a mole of eggs, though that would be an insane amount of eggs since a mole is equal to 6.022 x 10^23 of something.

But the point is that the mole is a unit and it makes accounting for molecules much simpler. Here’s a chemical equation to help illustrate this idea:

2Na + Cl2 –> 2NaCl

*The 2 in Cl2 is meant to be thought of as a subscript

The coefficients on the products and reactants represent the mole ratios of said products and reactants. The mole as a unit can be replaced by the term “molecules” in order to simplify the thought process behind the reaction (i.e. it takes two molecules of Na to react with the diatomic molecule Cl2 in order to produce 2 molecules of NaCl).

However, using the term “molecule” in place of “mole” is only intended to simplify the reaction conceptually. In reality, 2 moles of Na react with 1 mole of Cl2 to produce 2 moles of NaCl. A mole is a lot larger than a molecule since it is a unit meant to symbolize the amount of molecules in 12 grams of Carbon-12, Avogadro’s Number.

So there you have it. The mole is just a unit to help us solve problems. It’s not meant to confuse anyone. Actually, it’s meant to make numbers easier to work with. Isn’t it funny that it took me one session with a GSI to understand this when I didn’t learn it fully in two years of high school chemistry? Oh well, all’s well that ends well!

Hope everyone is having a wonderful day because I know that mine just got a whole lot better!

Berkeley Bound

This past Sunday was the day I had thought would never come, and was simultaneously subconsciously dreading: move in day for UC Berkeley. Don’t get me wrong, I’m super excited to be here at Cal. I’m also super NOT excited to only get to see my family every couple months. Apparently I was much more attached to my family than I realized which is definitely not a bad thing as it means that they raised me right.

Right now the transition to becoming a “grown-up” has been a little rough without my parents directly behind me, always having my back. But I do know that things will get better once I adjust and I’m sure that I’ll have an awesome freshman year and maybe even be a bit sad to leave Berkeley come next summer.

Tomorrow is my first day of class so that means I’ll get to sit in on my first chemistry lecture! Yay (or not yay, I can’t tell yet)! Hopefully all goes well and I conquer Berkeley chemistry rather than have it conquer me. It’s always best to be positive.

This was a super short post, but it’s just an update to how my life is going and a note to suggest that many more chemistry posts will be coming as I delve into General Chemistry at Berkeley.

Go Bears!

Chemistry Thoughts: The Relationship Between Volume and Pressure

The countdown has begun. It’s currently T minus 7 days till I head off to Berkeley, but today is exactly the day that my chemistry panic has set in! UC Berkeley has notoriously difficult classes but the course I’ve heard about the most by far has been Chemistry 1A/1AL. Of course this means that’s the exact course I have to take my first semester in order to satisfy some requirements for medical school and my actual major.

On the bright side, I can get in a little review before I go to my first chemistry class so I don’t have a panic attack in the lecture hall, so here we go…

Boyle Oh Boyle, This Is Going To Be Good!

The most fundamental relationship between volume and pressure is illustrated through Boyle’s Law. The law is written down in several convertible forms, but we will consider it in the elementary format:

pv = C 

*p = pressure, v= volume, C= constant

The reason I chose the format pv = C is that it clearly displays the inverse relationship that pressure and volume have with one another. In mathematics, an inverse equation is shown as y = k/x, where k is a constant. Similarly, if we take the formula for Boyle’s Law and manipulate it by dividing the constant C by volume v, we will get the equation p = C/v. It’s an inverse function!

The inverse relationship means that if volume were to increase, pressure would decrease, and vice versa. Or, if pressure were to increase, volume would decrease, and once again vice versa!

If you think about it, this makes a lot of sense. Imagine a box that houses some gas, let’s say hydrogen.

If we were to decrease the size of the box, meaning that we are decreasing the volume without changing the number of particles, then there is less space for the particles to move around without colliding. Pressure is determined by the number and force of collisions so more collisions from having less volume means greater pressure!

Changing volume in the opposite direction would work as well.

If we were to increase the size of the box, meaning that we are increasing the volume without changing the number of particles, then there is more space for the particles to move around without colliding. Less collisions therefore equates to less pressure overall!

 

This is the basic point that Boyle’s Law makes but the applications, in my opinion, go so much farther than this. Hopefully if I understand this fundamental point, I’ll understand the math involved in Berkeley’s chemistry program! Thanks Charles Boyle!

 

 

 

 

 

Smoothie Talk: Kale Bananza

It’s safe to say that I’ve once again become obsessed with smoothies. I mean, what better way to put the kale in my fridge to good use? This morning I decided to go for a more hearty smoothie, not like the usual berry blends I concoct. I wanted to get in a good amount of green veggies and protein while still having a sweet morning snack, so I chose a few elements to tie in together that I hoped would taste yummy and keep me energetic/full till lunchtime. Lately I’ve been having a lot of trouble staying full after breakfast and because I’m beginning to workout in the mornings it’s really important that I have a filling meal to start off the day.

Without further ado, here is my Kale Bananza smoothie!

---

Prep Time: 5 minutes

Total Time: 5 minutes

---

Ingredients:

2 cups kale

1 banana, chopped

2 tbsp peanut butter

1 tbsp cinnamon

2 tbsp Greek yogurt

1 cup filtered water

---

Instructions:

1. Combine kale, banana, peanut butter, cinnamon, Greek yogurt, and water into blender.
2. Blend all ingredients until smooth consistency is achieved.
3. Pour into cups and enjoy!

Chemistry Thoughts: Avogadro’s Law

Lately I’ve been thinking about Avogadro’s Law (SPOILER ALERT: I am probably/definitely a nerd). When I was taking chemistry honors and AP Chem in high school I accepted Avogadro’s Law as a universal fact, the very definition of a law. There was so much more information in my textbooks that I needed to learn and I took the easy way out, not caring about understanding why any of the gas laws had to be fundamentally correct. In short, I left the proofs to geometry.

Of course now that I’m a recently graduated high school senior with absolutely no summer homework and way too much time on my hands, I’ve been going back to things that I wish I had time to do when I was in high school: cooking, hanging out with friends, reading, LEARNING THE EXPLANATIONS BEHIND DIFFICULT CHEMISTRY CONCEPTS.

And so, here we return to Avogadro’s Law. The definition of Avogadro’s Law is that equal volumes of gas, held at constant temperature and pressure, contain equal numbers of molecules.

A superficial glance at this statement and I wholeheartedly agree! Equal volumes of gas must have equal numbers of molecules because…well…duh. A few minutes later and suddenly I’m thinking about molar mass and stoichiometry and the relationship between moles and volume and now I’ve opened up a massive black hole and I have no idea where I am or why there are 22.4 Liters of gas per one mole at standard pressure and temperature. Basically, I need help.

Thank goodness for the internet because otherwise I would be sitting in my room for a week with marker stains on my face and crumpled up papers surrounding me, just trying to find an explanation for Avogadro’s Law.

Without further ado, here is a concise look at Avogadro’s Law:

Let’s assume that we have 1.00 Liter each of nitrogen gas and hydrogen gas in separate containers. We have also held both temperature and pressure constant in each of the containers.

Hydrogen and nitrogen particles have different masses (1.01 g/mol H and 14.00 g/mol N) which means that they have different sizes, nitrogen being the larger atom. However, we will soon learn that size is independent of this particular concept.

Pressure of a gas is determined by the average kinetic energy of gas particles and the number of particles present. The average kinetic energy in each container must be the same because the temperatures of the containers are the same.

*Average kinetic energy = (1/2)(m)(u²rms)

*u_{rms= root mean square speed}

The size of the particles doesn’t change the average kinetic energy of each container because smaller particles will move faster and larger particles will move more slowly, averaging out the kinetic energy.

So, if kinetic energy is the same for each of the containers, the only difference that would change pressure is the number of particles. BUT we already established that the pressure is equal in both containers. Therefore, the number of molecules in each container must be equal as well!

There we have it! The explanation is so much simpler than all the nonsensical thoughts and frustration that were building up in my head.

Volume and the number of particles in a gas are directly proportional; that’s the main point of Avogadro’s Law. The trouble for me was understanding that the average kinetic energy wouldn’t change according to different-sized particles, unless temperature changed.

Hopefully in two hours I’ll still feel that this explanation is simple.