Drawing Isomers

Posted Leave a commentPosted in Homolog and isomer, Organic chemistry, Uncategorized

Drawing isomers is a skill we should expect to develop in a Chemistry class. In case you’re not sure what are isomers, they are basically structures that have the same chemical formula (same number of atoms) but are connected differently, therefore, having different structural formula.  The best way to explain how to draw an isomer is to use an example. In this case, we’re going to use C6H14. A tip (Tip #1) that I find useful when drawing isomers is to identify the functional groups present in the given formula. Looking at C6H14, it basically consists of only carbons and hydrogens, making it a hydrocarbon. Now, which type could it be though – is it an alkane, alkene or alkyne? We can figure out which general formula (alkane, alkene or alkyne) C6H14 fits in. The general […]

SI Prefixes mnemonic

SI Prefixes

Posted Leave a commentPosted in Calculations, Uncategorized

Need to convert between prefixes like from picosecond to microsecond? Or kilometer to milimeter? Do you need to memorize the SI prefixes? Find it difficult to remember the letters/symbols, sequence and exponent value? If you answered yes, then you are not alone. My students join you in this struggle. That’s why I developed a mnemonic to help them memorize all 12 prefixes they need for the course. So, here we go, introducing the 12 prefixes: – Tera – Giga – Mega – kilo – hecto – deca – deci – centi – mili – micro – nano – pico – Here’s the thing, each of these prefixes have their own abbreviation/symbol. The first three (Tera, Giga, Mega) are abbreviated with 1 upper case letter (T, G and M, respectively). Then, the rest are 1 lower case letter (k, h, d, c, m, n, p), except deca (da) […]

Density formula

Density – Why should we care?

Posted Leave a commentPosted in Calculations

What is density? It’s mass divided by volume. The more mass you can fit into a fixed space, the denser it is. Let’s say we have two same size boxes. We stuff in feathers in one of the boxes and stones in the other box of the same size. Which is denser? Of course, the box with stones is denser since stones weigh more than feathers. So why is density important? Can you think of an example or two that involve density? Density can affect whether something will float or not (hot air balloon, boat, ice in drinks), which layer will be on top (oil spill in the ocean, lava lamp, vinaigrette), identity/purity of a substance (purity gold), to name a few. It’s present in our daily lives more than we may have realized. I relatedthree […]

Flow chart for classification of matter

Classification of Matter

Posted Leave a commentPosted in Uncategorized

Pure substance and mixture. Element and compound. Homogeneous mixture and heterogeneous mixture. How are they different? Does it MATTER? Yes! WHY? How to classify them? You’re in luck! Ask two questions and you can easily classify matter into element, compound, homogeneous mixture and heterogeneous mixture. Let me show you how. Let’s classify one of the recipe I’m going to try. Looks like I’ll be grilling the seasoned chicken on aluminum pan and cover it with aluminum foil. Before that, I’ll need to season it with salt, tumeric powder and other spices. Let’s start with aluminum foil. Refer to the flow chart at the top for the series of questions and classification.  The first question we should always ask is, “Does it have fixed composition?” Do we know what aluminum foil is made out of? Yea, it’s […]

Easy way to classify if a change is physical or chemical change.

Changes…Changes…Changes…Is it Physical or Chemical?

Posted Leave a commentPosted in Uncategorized

Are you curious if the changes that occur around you is physical or chemical? What’s the difference between physical and chemical change? It all lies in whether a new substance was formed during the change (refer to the flowchart above).  If a new substance is formed, then the change is chemical. Otherwise, the change is physical. Here’s a more thorough list defining both changes: I walked through examples from my morning routine and classified them as physical and chemical changes in this video: Want to test out your skills? Each practice set consists of 5 questions. Practice #1 Practice #2 Practice #3

How to predict number of bonds each element makes

How to Predict number of bonds each element forms

Posted Leave a commentPosted in Bonding

Caution: This method works well for elements in Rows 1 & 2. Elements in row 3 and above may deviate from the guidelines as they can exceed octet. There’s a general guideline that is helpful in figuring out the number of bonds each element makes. This comes in handy especially when drawing Lewis structures. It’s called the HONC rule, or sometimes known as HONC 1234 rule. The number refers to the number of bonds each of the element makes: Hydrogen makes 1 bond, Oxygen makes 2 bonds, Nitrogen makes 3 bonds and Carbon makes 4 bonds. These four elements are widely used when it comes to drawing Lewis structures at introductory chemistry level. You might be curious to know why those elements make the stated number of bonds. It’s pretty simple if you look at their […]

Writing formula for ionic compounds

Posted Leave a commentPosted in Formula

When ions of opposite charge get together, they form ionic bonding. Writing the formula for the ionic compound is pretty straightforward. The critical information you’ll need is the charge that each of the ions will form. If they are provided, then life can’t get any better. If not, you’ll need an extra skill to figure that out. Not tough, but may require slight memory space. I’ll post more about it soon. Meanwhile, here are some commonly used ions: Back to writing the formula, I find the cross-over method (aka criss-cross method/rule) the best when it comes to writing a foolproof formula. I mean who doesn’t want to get the formula right 100% of the time? So here goes: Write out the ions: Cation on the left, anion on the right. Cross the number in the […]

Let’s name those organic suckers (compounds)!

Posted Leave a commentPosted in IUPAC nomenclature

Do you get overwhelmed when it comes to naming organic compounds? Or do you get excited and accept the challenge of naming them? When I was young(er), I used to dread naming them. Couldn’t be bothered spending time learning the rules (they always seem endless and filled with lots of surprises/exceptions). It was much easier to brush it off claiming it’s not important and will not come in handy. Well … that worked for a while until I chose Chemistry as my major in undergraduate and later turned it into my career! Ha! Time to get serious and learn to name those suckers. Many organic compounds later… It’s actually very exciting once you figure out the basics. I do empathize with anyone who is facing the same lack of love for naming compounds using IUPAC […]

How to draw organic compounds in expanded, condensed and skeletal structural formula

Organic Chemistry 101: Drawing the structures

Posted Leave a commentPosted in Organic chemistry

One of the basic skills we need to acquire when learning organic chemistry is the ability to decipher the drawing that illustrates the organic compounds. Sometimes they come in lines with letters, sometimes grouped together and maybe sometimes, hardly any letters at all, just lines. Being able to “read” these structures will pave the road to success in conquering whatever is next – identifying functional groups, drawing isomers, naming compounds, etc. Basically, there are 3 common ways organic compounds are drawn. They are: Expanded structural formula Condensed structural formula Bond-line/Skeletal structural formula When we graduated from drawing Lewis structure successfully, chances are high, our structure looks like this (the “expanded” image below). We draw out all of the bonds connecting all of the atoms in the compound. Sometimes, we may even include the lone pairs […]

Flowchart to classify homolog, isomer, same compound or not.

All about Homolog and Isomer!

Posted Leave a commentPosted in Homolog and isomer

Along with knowing the basic functional groups that are present in organic compounds, chances are high you will encounter these two concepts: Homologous series and Isomerism. Homologous series (homolog for short) is like a family consisting of siblings that possess the same/similar traits. For example, the most basic homologous series consists of unbranched alkane. Check out the list the first 10 siblings below. Notice that their structure look kind of the same? The only difference between one sibling and the next one is the extra CH2.  That’s one of the characteristics that define homolog. Also, homologs share the same functional group and general formula (CnH2n+2 in our case of unbranched alkane). Since their structure is so similar, that contributes to them having rather similar physical properties – like boiling point, melting point, physical states, density, etc. […]