We found 70 articles

How to draw a molecular orbital diagram (and what it can tell you)
A notoriously strange and elusive concept in chemistry: the molecular orbital. Its seemingly arbitrary patterns and applications appear in every chemistry course, yet it confuses almost every student. Here’s a step-by-step on how to draw a basic molecular orbital diagram and what it can tell you about the properties of the chemical bond between ...
The case for physical chemistry
For many years in academia, I have been teaching courses in what I consider the "Holy Grail of Chemistry" - Physical Chemistry (which is composed of Quantum Chemistry, Statistical Thermodynamics, Kinetics, and Chemical Dynamics. In these courses, physics, mathematics, biology, and chemistry blend together in an exquisite way to provide a ...
Intermolecular forces: a basic, ground-up approach
Intermolecular forces (IMFs) are “electrostatic” interactions between molecules – a result of all the charges floating around and interacting in the system. IMFs influence the properties of substances that we can observe and interact with – for example, the phase of the substance or its boiling point.
The hydrophobic effect, explained
If we had to pick one go-to answer to explain as many things as possible in biochemistry, it would probably be “the hydrophobic effect.” It’s responsible for protein structure and function, cell membrane organization, and the distribution of drugs and metabolites. It’s often an important consideration in drug design. But what is it, and how does ...
How to use the ideal gas law
While you might not think about it very often, gases are everywhere around us, from the air you breathe to the natural gas you might use to heat your home. To use gases safely and effectively, chemists use the ideal gas law to understand how much gas is in containers and pipes.
I’m failing chemistry—does that mean I shouldn’t be a doctor?
Ask almost any premedical student about chemistry, and you’ll get the same set of reactions. If they haven’t finished the chemistry prerequisites, it's a gulp and a look of fear. For those who have completed chemistry and are still premed, it's a sigh of relief: the hardest part is over! And for those who are currently struggling in chemistry ...
Why does chemistry seem so difficult?
I have greeted over 1,000 students to my classroom throughout the 20+ years of teaching AP Chemistry, and the number one question I hear is “Why is chemistry so hard?” I have several responses to that question that I have offered to my students. But first, I want you to read each bullet below and notice which one resonates with you:
Chromatography: purifying your understanding
Maybe you were studying for the MCAT or just in your college chemistry lab when it dawned on you: why are there so many different types of chromatography? What do they have in common and what are their differences?
How to solve an empirical formula problem
In this blog post, we will review how to determine the empirical formula of a compound using the mass percentages of the elements from which it is formed.
Quantum numbers
In this blog post, we explore the four quantum numbers, which allow us to describe the properties of each electron within an atom. According to the Pauli Exclusion Principle, no two electrons can share the same combination of quantum numbers. A carbon atom has six electrons, for example, and each of these electrons can be described by one of six ...
A painless introduction to VSEPR theory
Today we will discuss VSEPR (pronounced “vesper”), which stands for valence-shell electron-pair repulsion. The basis of VSEPR is that the electrons in bonds and lone pairs repel each other. To minimize the instability that results from these repulsions, a molecule will adopt the shape that places electron groups as far apart as possible. VSEPR ...
Tips for success in organic chemistry courses
Organic chemistry is historically considered a “weed-out” class for pre-medical students and often the cause of much frustration for students. After spending 3 years during college serving as a teaching assistant and tutor for organic chemistry courses at my undergraduate university, here are some tips for studying for your organic chemistry ...
Drawing the chair conformation of a pyranose ring
In this blog post, we will complete the following example problem:
How to balance redox reactions in acidic and basic solutions
Balancing redox reactions is an essential skill for the Chemical and Physical Foundations section of the MCAT, the GRE Chemistry Subject Test, and the AP Chemistry Exam. Today, we will learn how to use the half-cell method for balancing redox reactions in acidic and basic solutions. We will first balance a redox reaction in acidic solution, then ...
Puzzling out ionic compounds
Although there are lots of tricks that people use to write chemical formulas for ionic compounds, the best way to do it is to really understand what’s going on – that way, you’ll never use a shortcut that doesn’t work.
A step-by-step approach to dimensional analysis
Dimensional analysis is the best way to do math in chemistry. With dimensional analysis, you don’t need to memorize formulas, and you can easily check your work for every problem. Because this skill is so important, it’s crucial to have a step-by-step method that you follow every time you do it.
Using pKa to predict protonation state
When you've learned about pKa, you've most likely used it in acid-base calculations. However, some exams may ask you to apply a conceptual knowledge of pKa to predict whether a chemical compound is charged or uncharged.
S’more fun: simplifying limiting reactants using chocolate
Stoichiometry: it’s the bane of many chemistry students’ studies. It’s so easy to get tangled up in a jumble of numbers without any idea of what’s actually going on.
Cell component spotlight - The ribosome!
What is the ribosome? I find the parts of the cell are easier to keep straight if you get to know each one of them a little better. Don’t be scared; they’re your friends! Let’s talk about the ribosome.
I just want to be a doctor, so does organic chemistry really matter?
Imagine: you’ve made it through your first semester or two of undergrad and weathered all the storms that come with this transition. And, now you find yourself facing a dreaded academic giant that has stricken fear in the hearts of scores of pre-medical students. A chemistry course unlike any other. If you are anything like most pre-medical ...
High school chemistry: What is it? Can I be good at it?
The word “chemistry” inspires so many emotions. To some, it brings about the excitement of mixing together glowing liquids and crafting the perfect radioactive potion that, when consumed, will turn you into the Incredible Hulk. To others, it’s discombobulated numbers and letters on a piece a paper in a classroom, a concatenation that strikes fear ...
So, what is chemical engineering for, anyway?
Chemical engineering is a comprehensive and vast field of study with far-reaching impact. I have been a practicing chemical engineer in the biotechnology industry for the last 5 years, and prior to that, I earned my doctorate in chemical engineering at the University of Wisconsin, Madison. Over the last 10 years, I have seen the evolution and ...
Complex solution composition problems: knowing where to start
Thanksgiving dinner conversations can be uncomfortable… but solution composition problems don’t have to be! Recall that a solution is a homogenous mixture of two or more substances. Chemists have come up with many ways to describe the composition of a solution. Some ways are more appropriate than others depending on the situation.
A guide to limiting reactant problems... using sandwiches
An everyday limiting reactant problem You’re expecting company and totally forgot to go grocery shopping. What on earth will you feed your guests? Sandwiches! You have some ingredients to whip up some sandwiches. So, let’s assume you are going to go through with making these sandwiches. You need 2 slices of bread, 3 slices of meat (can’t be ...
Dimensional analysis: why the factor-label method is a lifesaver
Ever lost points on a test because you forgot to write the units? Rightfully so! Numbers have no meaning without their units of measurement. Two can be greater than 12. Three can equal one. This is all dependent on the unit of measurement being used. In your general chemistry class, you will encounter measurements of all sorts. These measurements ...
Electron configurations: a must know hack
Imagine’re taking your general chemistry midterm and you’ve decided to shuffle through the exam and complete all the hard things first. You’ve totally underestimated how much time those problems were going to take you and now you have three minutes left to write the electron configuration of 10 elements. Untimed, this would be easy to ...
Formal charge: what they didn’t tell you in your chemistry class
Formal charge is the charge that a bonded atom would have if its bonding electrons were shared equally. Note:
Orgo 2 strategies: “taking home” carboxylic acid derivatives
I’ve already covered how to easily manage carboxylic acid derivative formation and manipulation using the Reactivity Hill. Say we’re tired of whatever derivative we just created and want to bring the derivative back to its parent acid (the particular acid the derivative came from). There are two ways to “take home” any acid-derivative. We can ...
Organic Chemistry: This Subject Gives You Alkynes of Trouble!
Although some people genuinely enjoy it, organic chemistry is stigmatized as the bane of every science major's curriculum. Before you actually take one or two courses in this subject, the horror stories that you've heard from those who have already taken these courses fill you with anxiety and leave you fearing the unknown. I'm not going to sugar ...
Golden rules to nuclear magnetic resonance spectroscopy (NMR) analysis: part 1
Nuclear magnetic resonance spectroscopy, or NMR, is a fundamental analytical technique used by chemists to determine the structure of organic compounds. Unlike other analytical techniques, such as infrared spectroscopy or mass spectroscopy, NMR allows for the complete interpretation of molecular structure and can be quantitative.
Orgo 1 Strategies: Understanding Hybridization
Your professor gives you the below molecule. Can you quickly determine the hybridization of every atom? Determining and understanding hybridization in Orgo 1 isn’t a futile practice. It’s an idea key to understanding mechanism and reactivity all the way through Orgo 2. Thankfully, the rules of thumb used to determine an atom’s hybridization are ...
Two ways to determine equilibrium position in organic chemistry
A common exam question that comes up in both Orgo 1 and Orgo 2 requires students to determine a reaction’s equilibrium position. The question usually looks something like this:
Orgo 1 strategies: finding and comparing alkene hydration products
We all know Orgo 1 professors love stereoisomers. Consider the equation A + B = C. Most professors expect you to fill in the question mark with all possible products and then indicate the major product(s), while other professors may provide you a potential C and then ask you if the statement is True or False.
How to get oriented to organic chemistry: 7 pillars of the course
Organic Chemistry (OChem or Orgo) seems like a scary course. But it should not be if you know what to expect. This road map is your guide to orientate yourself to Orgo1. It teaches you about the main topics covered in Orgo1 in the typical order they are taught in class. So, take a breath and sit back as you read, skim, or view the images that ...
Orgo 1 Strategies: The Power of Bromine in Synthesis
Whether you’re trying to accomplish a substitution or elimination in your synthetic scheme, there’s no getting around that a good leaving group must be involved. You’ll have a host of ways to introduce leaving groups by your final exam. Some reagents will invert chiral centers (e.g. SOCl2/pyridine, PBr3) in the process, and others won’t.
Orgo 1 Strategies: Two Red Flags to Guide Your Synthesis
So your professor says your Orgo 1 final will have a few synthesis problems. The good news: you’ve only learned a handful of reactions. Namely, you’ve learned how to manipulate alkenes and alkynes, and you know a little about radicals, substitution versus elimination, and the chemistry of alcohols, thiols, ethers, and epoxides. The bad news: ...
Orgo 1 strategies: protocol for acid-base problems
Determining which of two molecules is more acidic is tricky if you haven’t yet organized those factors that influence acidity. The protocol is a method I learned from my mastermind Orgo 2 professor to keep these ideas in order when they come into conflict. Namely: Size is more important than Electronegativity, which is more important than ...
What is the phospholipid bilayer and what determines its fluidity?
All cells are surrounded by a cell membrane that forms a barrier between the cell and its surroundings. This membrane is often referred to as the phospholipid bilayer. As you can probably tell from the name, a phospholipid bilayer is made up of two layers of lipids. The fluidity of this membrane must be maintained within a certain range for the ...
Tips and mnemonics for memorizing amino acid structures
Learning amino acid structures is a challenging part of biology and biochemistry coursework. Many students feel totally overwhelmed by the task. The best way to master this skill is lots of repetition (here is a link to a Sporcle quiz that may help you with the repetition part) but it can be helpful to have tricks and mnemonics to get you started. ...
The five most essential tips for AP Chemistry review
Here are five tips to ace AP Chemistry -- you can begin right now!
How to solve an AP Chemistry question that stumped most test-takers
On average students scored 3.88/10 points on this question while only 1% of students got a perfect score. In this question, students are expected to know how to analyze the experimental data that is given and show an understanding of thermodynamics.
A basic guide to the AP Chemistry Exam
pic The AP Chemistry exam is on May 2nd, leaving less than two months to prepare! You might still be struggling with where to begin, and that’s how this blog post can help. In 2014, the exam was revised to focus on six big ideas in chemistry. The new format is intended to test your understanding of big picture concepts and apply them to the ...
A guide to deciphering chemistry arrows
Chemistry is confusing enough with IUPAC nomenclature procedures to know, and the difference between E/Z and cis/trans alkene descriptions, and so many other new terms, models, units, and symbols. But the most common and important symbol in chemistry is the arrow.
Visualizing Colligative Properties
To simplify colligative properties, picture what is happening when you dissolve a salt in water. We know that increasing the concentration of ions has an effect on the boiling and freezing points of water. How do you remember which way?
The basics of retrosynthesis
People often dismiss organic chemistry as “all memorization”. I disagree – organic chemistry is just a series puzzles based on a few basic concepts (electronics, sterics, orbitals) that come together to answer almost any problem you might encounter on your homework or tests.
The Chemistry Tutor: nine tips to get you through orgo
Many students find organic chemistry to be one of the most daunting classes that they take during college. And they’re right––it’s not easy! But with some good study skills, it’s possible for anyone to succeed and become a master organic chemist.
Study skills: the bionic power of mnemonic devices
Mnemonics: from the Greek “Mnemonikos:” of or relating to Memory.A device such as a verse or formula or rhyme used as an aid in remembering concepts. Named for Mnemosyne, the goddess of memory in Greek mythology.
How to make scientific writing intelligible
Many students struggle with scientific or technical writing, unsure how to present complicated and number-heavy information in readable prose. Commonly, students fall into the trap of vomiting data onto the page without very much connecting prose to help the reader understand the material. This forces the reader to shoulder the burden of figuring ...
How to tell if a bond is inter- or intra-
As you go over the material in your chemistry course or your SAT/AP test prep, you most certainly spend a lot of time learning about bonds—what they are, how they differ, how strong they are, and so forth. Also, you have probably read about them being classified into intramolecular bonds and intermolecular bonds. During my many one-on-one ...
Biology and chemistry tutor: acidity, pH and pKa
When it comes to the advanced science classes you will take in college, there is usually a clear distinction between the kinds of material covered in each of them. For example, the material you cover in biology classes is quite different than that covered in chemistry classes. However, there are some topics that know no boundaries––for example, ...
Cooking with moles in chemistry
Anyone who has had some contact with chemistry knows how important the mole is to chemistry.
Chemistry Tutor: Approaching the AP Chemistry Exam
Over the last two years of your high school career you’re typically faced with an onslaught of standardized tests. While many of these, such as the SAT, ACT, or SAT II tests are required as part of your college application package, the AP exams are somewhat unique in that they can actually affect your college coursework by placing you into higher ...
The Path to a Cure: Chemistry in Practice
We’ve spent some time in past weeks here talking about how to approach a degree in chemistry, but what we haven’t really talked about is what you can do with that degree. Certainly, chemistry majors (and Ph. Ds) can follow academic careers, either as chemistry tutors, school teachers or research professors, but these opportunities aren’t really ...
How to identify unknown solutions in a chemistry lab
One of the most common general chemistry lab experiments, both in advanced high school classes as well as introductory college courses, is the identification of a series of unknown chemicals. As a chemistry tutor, I am well equipped to break it down for you.
Chemistry Tutoring: Demystifying Organic Chemistry
While some may feel that no graduate students can adequately describe their research to a non-specialist in a few minutes, organic chemists (specifically, synthetic organic chemists) often find themselves at a much larger disadvantage for making casual conversation about what we do. Even as chemistry tutors who are used to teaching and talking ...
Tips from a Biology Tutor in Cambridge: Taking science tests
We all know that science tests can be challenging. Not only is the content broad and sometimes difficult to master, but the tests themselves can be tricky and confusing. How many of you have run out of time because you got stuck on one confusing question that was probably low yield? Science tests are also notorious for having poorly articulated ...
Keys to Chemistry: Practice Problems with a Chemistry Tutor
Organic chemistry can be frustrating, but it doesn't have to be if you find an able chemistry tutor or study group to help you with your class. Not sure where to start? Sign up for a free consultation!
Making the jump in chemistry: PhD application consulting
Let’s take a closer look that what constitutes an application, and what you’ll want to focus on as you get your applications together. While some schools have slightly different variations on this theme, generally, your application for a graduate degree in chemistry will consist of, in order from most to least important:
Making the Jump in Chemistry – Selection & PhD Admissions
Let’s say that you’re a junior or senior in college, and you’ve pretty much decided that you’re heading to graduate school for chemistry after you finish your studies.That means it’s time to consider where to apply and what your application package will look like. In contrast to applying to colleges, applications for graduate schools are much more ...
Making the Jump in Chemistry – Preparing for Grad School
Your author is not only a chemistry tutor, but is more than three years in towards a doctoral degree in organic chemistry. For advanced chemistry students, a frequent question is “Do I need to go to grad school?” The short answer is, yes, for chemistry majors grad school is essentially a requirement. But that being said, it is a lot of school, and ...
Making the jump in from High School Chemistry to College Chemistry
As a chemistry tutor here in Cambridge, one of the questions I’m frequently asked is “What is chemistry like in college?”
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