Chemistry

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Basic Chemistry 1

by Oren Lahav

Basic Chemistry, Part 1

What comes to mind when I say chemistry?

Boring lessons in high school? Cool experiments with explosions? Test tubes full of liquids in various colours? Chemistry has all that, and more.

Chemistry is the science of substances and matters, and how they interact in our world. It sounds nice and simple, but in reality it's a broad and complex discipline.

In terms of the three major sciences, chemistry builds upon and uses a lot of the theory from physics, and in turn is used and applied extensively in biology, so it serves as a bridge between the general world and real life. This makes chemistry cool and important, and earned it the nickname of "the central science".

Chemistry involves substances. The most basic substance in nature is called an element. Elements are the basic building blocks of all chemical substances, so you can think about them like Lego® pieces. All red pieces are element 1, and all blue pieces are element 2. You can combine elements 1 and 2 to form different stuff, from a simple blue and red piece to a Lego® train.

All elements are made of atoms, and one atom is the tiniest piece that retains the properties of its element. An atom looks like this (well sort of, atoms are much too tiny to actually see):

It has a nucleus, which contains protons, positive particles, and neutrons, which are neutral. It also has orbiting electrons, tiny negative particles. To learn a lot more about the atom, take a look at my History of the Atomic Theory series.

The number of protons of an atom gives you the atomic number, which is unique for each element. For example, the element Hydrogen has an atomic number of 1, so it has 1 proton. The element Oxygen has atomic number 8, so it has 8 protons. The element Mendelevium has atomic number 101, so Mendelevium atoms have 101 protons in its nucleus.

The number of neutrons in the nucleus combines with the number of protons to give you the atomic mass of an atom. Atomic mass is not measured in kilograms or milligrams since atoms are ridiculously small, so instead atoms are measured relative to each other's mass, with Hydrogen being the smallest element of atomic mass 1 amu (atomic mass unit). So for example, if Phosphorus has an atomic number of 15 (i.e. 15 protons) and an atomic mass of 31, it would have 31-15=16 neutrons in its nucleus.

Some elements have isotopes, which are atoms that have the same number of protons but a different number of neutrons (and thus a different atomic mass). These isotopes generally share the same chemical properties, because they have the same number of protons and electrons in a neutral state.

The number of electrons of an atom determines its overall charge, and facilitates compounds, but we'll get to this later.

So, these are your elements. The best way of presenting all chemical elements would be to use the Periodic Table. This table, created by Mendeleev, uses rows and columns to divide elements into distinct groups that share similar properties. There are various ways to group elements, and we'll discuss these more thoroughly at some later point.

Elements can combine to form compounds. A compound is has 2 or more types of elements in it that are bonded together in a fixed proportion. An example of a compound would be water, in which every oxygen atom is bounded to exactly 2 hydrogen atoms. Compounds can be classified in many ways, such as by the type of bonds they include. A compound is generally represented by a chemical formula that explains the types of elements involved and their proportions- for example, water is H_2O.

The smallest particle that retains the properties of an element is called a molecule. Using water as our example, a glass of water contains tons of molecules. One water molecule is simply one oxygen atom bonded with 2 hydrogen atoms. Splitting a molecule into separate atoms will cause it to lose the properties of the compound it used to represent. Molecules have specific sizes and geometrical shapes.

Molecular mass denotes the relative mass of a molecule compared to other molecules and atoms. It's calculated simply as the sum of the mass of the atoms involved. For example, a water molecule with 1 oxygen atom (16 amu) and 2 hydrogen atoms (1 amu each) has a molecular mass of 18 amu.

Chemical substances are either compounds or elements. The have consistent composure, and their atoms or molecules cannot be broken down without a chemical reaction. Mixtures, on the other hand, can contain several substances and can be separated using simpler means.

Homogeneous mixtures are ones that have definite and consistent properties. Think of them like a veggie-shake, which has the vegetables cut so small and mixed up so that the shake has a specific consistency. Heterogeneous mixtures have inconsistent and non-uniform composition, like a salad- it's easy to see and separate the different vegetables.

That's enough for now! See you next time

Image Credits:by striatic, by brapps, by Clav, by LUZA, by Svadilfari

2 Comments
    jayakumar20
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    jayakumar20Mon, 30 Jun 2014 12:30:52 -0000

    how to score high marks in chemistry

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    msandi
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    msandiThu, 20 Sep 2012 10:45:22 -0000

    good help guys please add more and i want to join this class how can i?

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Last Updated At Dec 07, 2012
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