The life of a chemist is often filled with challenges. One of the largest challenges any chemist can face is the purification of a mixture. Let’s say you just finished running a chemical reaction.
Whether primary or secondary, historical sources are imperative if we are to gain a clear understanding of the events that shaped the lives that we lead today. What would our knowledge of the impact of the Norman Conquest be without the Anglo-Saxon Chronicle or the Doomsday Book? How else could we gain a precious glimpse into the lives of our ancestors without the 1881 census?
If you’re taking a chemistry class or even a general science class, chances are pretty good that you have a copy of the Periodic Table of Elements. It might be hanging from a wall on a poster, or inside the back cover of your textbook. All the strange combination of letters, all the numbers – it can be very confusing. It’s almost information overload, right?
A reaction may happen when two or more chemicals are mixed. Sometimes you have to add heat (energy) before the reaction will occur. Not all chemicals react together when they are mixed. We can tell a reaction has taken place if we see bubbles of gas, a change in colour, a change in temperature or a precipitate (a layer of solid in the bottom of the test tube that wasn’t there when you started). So vinegar (an acid) reacts with sodium bicarbonate – there are bubbles of gas and the test tube gets warm – but it doesn’t react with table salt (sodium chloride).
If I put a small piece of sodium metal in some water, a reaction occurs. The sodium fizzes and races around and there is an orange flame. Water and sodium hydroxide are both compounds. If you look at the Periodic table, you will see that sodium has a mass number of 23, oxygen has a mass number of 16 and hydrogen has a mass number of 1.
The chemical concept of a “mole” is very important to be able to perform calculations in chemistry. Remember from your class that an atom’ atomic weight refers to the number of grams in one “mole” of that material. What exactly is a mole? And how can we use it in calculations while not confusing ourselves with all the different units and conversion factors?