Author Archives: hangtime

Kinetic-Molecular Theory (KMT)

Throughout this course we've been talking about how gas is a bunch of bouncy little balls that go crashing into each other. I call it a mosh pit, the official name is Kinetic-Molecular theory, but both describe a situation which is the basis of all the gas laws to follow.

This video appears on the page: Intro to Gases

Intro to Gases

This chapter explains Kinetic Molecular Theory (KMT), defines pressure & density, and explains how molar volume and molar density at STP (22.4 liters) can make problems really short.

Part of the course(s): Physics ,Chemistry-General

Percent Yield

Yet another question type that is simple algebra on its own but gets confusing for students because it's usually tacked on at the end of a long stoichiometry or limiting reactants problem. Also a favorite for lab reports!

This video appears on the page: Limiting Reactant & Percent Yield

Intro to Limiting Reactants

This topic, also know as limiting reagents, is usually in the same chapter as sthoichiometry. That often creates confusion around these questions because they look an awful lot like stoichiometry problems. So in this video I'll show you how to spot the difference, and I'll show you how to do the various types of question that usually go along with these.

This video appears on the page: Limiting Reactant & Percent Yield

Limiting Reactant & Percent Yield

Once you know stoichiometry, there's all kinds of exciting and complicated questions your teacher can ask you on tests and lab reports!

Part of the course(s): Chemistry-General

Harder Stoichiometry Problems

This video covers the type of stoichiometry problem that will comprise the majority of your test, and which is used in limiting reactant (reagent) problems as well. In this type of problem, they'll give you a quantity in grams rather than moles, and then they'll ask for your answer to also be in grams. Not a ton harder than mole-mole, just adds a couple steps to the dimensional analysis.

This video appears on the page: Stoichiometry

Mole Ratios & Basic Stoichiometry

This video covers the first half of Stoichiometry to help you get a solid foundation in mole ratios, then it goes into the easier type of problem where they give you a quantity in moles (not grams) and ask you to solve for a quantity in moles (not grams).

This video appears on the page: Stoichiometry

Stoichiometry

This chapter covers all these problems, from basic mole ratios and mole-mole types to the more advanced mass-mass (gram-gram).

Part of the course(s): Chemistry-General

Reaction Types You Should Memorize

Many of these reaction types (combustion, redox, synthesis, oxidation, decomposition, exothermic, endothermic, rust, acid-base) will have whole chapters devoted to them later in the class. For now, you'll just need to know their names and how to spot them, and you'll need to be able to guess what products are formed on the right side of the equation.

This video appears on the page: Reaction Types

Reaction Types You Should Know

Just a bunch of vocab: combustion, redox, synthesis, oxidation, decomposition, exothermic, endothermic, rust, acid-base.

Part of the course(s): Chemistry-General

Bond Types In Solids

Ionic, Metallic, and Network Covalent bonds aren't technically "intermolecular" because they don't involve molecules, just atoms. Yet they tend to show up in the IMF chapter anyways (along with dipole-dipole, London, etc) because they have to do with why atoms form these particular types of solids. Also emphasized are the melting point and electrical properties of these types of solids, since these are common test questions.

This video appears on the page: Intermolecular Forces

London Dispersion Forces & Induced Dipoles

If you're looking at a molecule and can't figure it out the IMF's because it's not ionic or polar or dipole-dipole or hydrogen bonding or... Well, there's always London Forces! Literally, every molecule has London forces, so if all else fails, it's your default answer.

This video appears on the page: Intermolecular Forces

Dipole-Dipole & Hydrogen Bonding

These are the stronger type of intermolecular force, and are the reason that water and alcohols are liquids at room temperature. This video covers what these forces are, why they matter, and how to spot them.

This video appears on the page: Intermolecular Forces

Intermolecular Forces
Dipole-Dipole
Hydrogen Bonding
London Forces
Induced Dipole
Metallic Bonds
Network Covalent
Ionic Structure
Properties of Solids
Liquid vs Gas

This chapter covers everything about why particular elements and compounds form solids, liquids, or gases, from the forces that make them want to "stick together" to the kinetic heat/rattling which makes them want to break apart.

Part of the course(s): Chemistry-General

Determining If Molecule Is Polar

Even if the individual bonds which make up a molecule are polar, you can still have a molecule which is overall nonpolar because all the little dipoles cancel each other out. In this video we'll use everything we know about Lewis Structures, molecular shape, and electronegativity to determine if molecules are polar.

This video appears on the page: Electronegativity & Polarity

Using Electronegativity To Determine Bond Type

In this video we'll introduce the concept of electronegativity -- basically how big of an electron hog each element is and how well it shares with others -- and use it to determine if bonds are nonpolar covalent, polar covalent, or ionic.

This video appears on the page: Electronegativity & Polarity

Electronegativity & Polarity

This chapter outlines electronegativity, and explains how to use it to determine if individual covalent bonds are polar or nonpolar, as well as whether whole molecules are polar.

Part of the course(s): Chemistry-General

Formal Charge

Normally, when you say an atom has a certain charge, you're talking about an ion. Formal charge, however, is a sort of meta number that you can calculate for any atom in a molecule. Although it doesn't represent measurable, actual charge, it can give you an idea as to whether a particular Lewis structure is stable or reasonable.

This video appears on the page: Formal Charge

Formal Charge

This chapter covers how to find the formal charge on the atoms in a molecule. If this isn't on your syllabus, don't bother.

Part of the course(s): Chemistry-General

Molecular Shape Examples

Now that we know VSEPR theory like the back of a poodle's head, in this video we'll do lots of examples, starting with Lewis structure. We'll also cover some common mistakes that you don't want to make, and advice on how to avoid them.

This video appears on the page: Molecular Shape & VSEPR Theory