What do you do if you don’t know the concentration of a solution? We use a method called titration to determine how many moles are present in the solution of an acid or a base by neutralizing it. A titration curve is when you graph out the pH as you drop it in the solution.

Now let’s take a look at the forces between the molecules themselves. There are four main interactions which really come down to different ways of having opposite charges attract each other.

The periodic table is more like a filing cabinet that tells you everything about the structure of the atom, its properties and how it behave in chemical reactions. With just a quick glance, you will soon be able to tell how the electrons are organized around the nucleus and also predict how the atom will interact with others.

Ionization energy is the energy needed to remove electrons from an atom.

The Bohr model is useful when we want to tell how reactive an element is, but it doesn’t really work to explain how the electrons are organized around the nucleus. The quantum model is the one used today by scientists.

The number of electrons in the outermost shell tells you how reactive the atom is because it tells you how many it needs to feel full, or how many it can lose. Valence electrons are the highest energy and furthest out electrons. In general, elements are less reactive when their outermost shell is full.

The “mean free path” is the average distance a gas molecule travels between collisions. If a molecule has a diameter “d”, then the effective cross section for a collision is “π d²“. This is used mostly with the Kinetic Theory of Gases, and is a good estimation of how particles move in a gas.
Please login or register to read the rest of this content.

Click here to go to next lesson on Kinetic Molecular Theory.

If you had a choice between a glass of lemon juice or apple juice, most folks would pick the sweeter one – apple. Did you know that apples are loaded with malic acid, and are actually considered to be acidic? It’s just that there is so much more sugar in an apple than a lemon that your taste buds can be fooled. Here’s a scientific way (which is much more reliable) to tell how acidic something is.

Acids are sour tasting (like a lemon), bases are bitter (like unsweetened cocoa powder). Substances in the middle are more neutral, like water. Scientists use the pH (power of hydrogen, or potential hydrogen) scale to measure how acidic or basic something is. Hydrochloric acid registers at a 1, sodium hydroxide (drain cleaner) is a 14. Water is about a 7. pH levels tell you how acidic or alkaline (basic) something is, like dirt. If your soil is too acidic, your plants won’t attract enough hydrogen, and too alkaline attracts too many hydrogen ions. The right balance is usually somewhere in the middle (called ‘pH neutral’). Some plants change color depending on the level of acidity in the soil – hydrangeas turn pink in acidic soil and blue in alkaline soil.

There are many different kinds of acids: citric acid (in a lemon), tartaric acid (in white wine), malic acid (in apples), acetic acid (in vinegar), and phosphoric acid (in cola drinks). The battery acid in your car is a particularly nasty acid called sulfuric acid that will eat through your skin and bones. Hydrochloric acid is found in your stomach to help digest food, and nitric acid is used to make dyes in fabrics as well as fertilizer compounds.

Click here to go to next lesson on Gravimetric Calculations.

The kinetic theory of gases assumes that all gases behave ideally, but we know that’s not really what happens in the real world. For example, real gas particles do occupy space and also attract each other, although these properties are more apparent at lower temperature because usually the particles have enough kinetic energy to zip by each other without worrying about the attractive or repulsive charges from other molecules. If the molecules move slow enough though, they do get affected by the push or pull of other molecules.

Also at high pressures, the molecules are so tightly packed together that they do start to have volume considerations that need to be addressed. So for a real gas, we can make calculations like this:

The kinetic theory of gases relates what’s going on with the motion of the tiny invisible molecules with the properties you can measure, like temperature and pressure. Kinetic means the study of motion, and for us, it’s the motion of the gas molecules.

Atoms are held together by bonds, and bonds take energy, so an atom that is bonded has less energy than if it was free floating around on its own. Energy is required to break a bond (bond energy). Energy is released when a bond is created. (We’ll use this idea again later when we talk about Lewis Dot structures.) Each molecule has its own bond energy which you can look up in a table in your chemistry book. For example, C-H bonds take about 100kcal of energy to break 1 mol of C-H bonds, so you’ll find bond energies listed in kcal per mol. If you look up C-C bonds, you’ll find 80 kcal/mol. And a double C-C bond is 145 kcal per mol.

This is a cool video from a Teacher’s Educational Channel in Europe I thought you might enjoy about the science of fireworks:

You can view the full video here: https://www.youtube.com/watch?v=3hNf8DRg5vQ

The “mean free path” is the average distance a gas molecule travels between collisions. If a molecule has a diameter “d”, then the effective cross section for a collision is “π d²“. This is used mostly with the Kinetic Theory of Gases, and is a good estimation of how particles move in a gas.
Please login or register to read the rest of this content.

Graham’s law tells is how gases move through porous materials, like air in a balloon. Ever noticed how balloons don’t stay inflated forever? That’s because the gas diffuses through the balloon skin itself. And if you take a good look, helium balloons deflate the next day, whereas normal air balloons will keep for a few days. Small helium molecules effuse through the tiny holes in the balloon skin much faster than normal air does.
Please login or register to read the rest of this content.

Avogadro’s Law states that 1 mole of every gas occupies the same volume at the same temperature and pressure. The mass of the gas might be different… one mole of helium is going to weigh less than one mole of nitrogen, for example, but the number of helium gas molecules is exactly the same as the number of nitrogen molecules, and both of them will occupy the same amount of space (22.4L) at standard temperature and pressure. At room temperature and pressure, it’s slightly higher (24 L).
Please login or register to read the rest of this content.

Gravimetric analysis is a technique through which the amount of the ion being analyzed can be determined through the measurement of mass. Gravimetric analysis depend on comparing the masses of two compounds containing the ion to be analyzed. Here’s an example:

A 3.46 g sample of limestone(CaCO3 ) was dissolved in 0.1M (HCl) solution like this:

Wa-hoo! You’ve completed the entire Chemistry Course!

Imagine a plate of spaghetti. The noodles slide around and don’t clump together, just like the long chains of molecules (called polymers) that make up slime. They slide around without getting tangled up. The pasta by itself (fresh from the boiling water) doesn’t hold together until you put the sauce on. Slime works the same way. Long, spaghetti-like chains of molecules (called polymers) don’t clump together until you add the sauce – something that cross-links the molecule strands (polymer) together.
Please login or register to read the rest of this content.

Potassium perchlorate is usually safer than chlorate salt, but it sometimes is hard to get it. In the past, the only supplier in the US makes ammonium perchlorate, the oxidizer that was used with the space shuttle booster rockets, and each shuttle launch required 1.5 million pounds of it, which was twice the annual consumption rate, so when there were a lot of shuttle launches, the fireworks market took a hit and it was near impossible to get any potassium perchlorate.
Please login or register to read the rest of this content.

Chemists want to control not only what comes out of a chemical reaction, but how fast the reaction occurs. For example, scientists are working to slow down the depletion rate of the ozone in the upper level of our atmosphere, so we stay protected from harmful UV rays.

The rate of the chemical reaction of a nail rusting is slow compared to how fast baking soda reacts with vinegar. Different factors affect the speed of the reaction, but the main idea is that the more collisions between particles, the faster the reaction will take place.
Please login or register to read the rest of this content.

Hydrolysis is a chemical reaction that happens when a molecule splits into two parts when water is added. One part gains a hydrogen (H+) and the other gets the hydroxyl (OH–) group. The reaction in the experiment forms starch from glucose, and when we add water, it breaks down the amino acid components just like the enzymes do in your stomach when they digest food.