Introduction :
In this blog post, I will be talking about the issues and things we learnt in class, and the theme for term 1 was - Models and Systems. Basically, we were introduced to the Periodic Table and the Atomic structure, something that would be rather new for most of us as during secondary 1, we we only touched on the surface of these 2 topics. We have learnt what are elements and compounds, that every thing is made up of atoms, but have we really understood deep enough? Well I would have to say I did learn a lot more regarding these 2 topics after the school lessons! Aside from that, we also learnt new topics, such as Chemical Bonding and Equation Writing.
Periodic Table
Now ever since Primary 5, I have been hearing classmates mentioning the Periodic Table, memorising the Periodic Table and all sorts. This year I finally got to clear all my doubts, and know actually what the Periodic Table is. I did have a brief idea what it was, but due to countless procrastinations and forgetfulness, I never really researched about it before, as easy as it is by just typing it into Google. The Periodic Table is actually all the elements known to man so far - both natural and man-made. The elements are arranged according to their order of increasing proton(atomic) number, which means to say the position of an element in the Periodic Table is actually related to it properties, such as proton number and electronic structure. The elements are also arranged from metallic to non-metallic character from left to right across a Period of the Periodic Table.
Each column in the Periodic Table represents its Group, while each row in the Periodic Table represents its Period.
Atomic Structure
So what I knew last year was that an atom is a basic building block of matter. Everything around us like plants, animals, air, water, sun, earth, planets and even people are all made up of atoms. It is the smallest unit of an element that still exhibits all the chemical properties unique to element.
According to my knowledge at that time, an atom consist of a nucleus, which I learnt this year is made up of protons and neutrons, surrounded by a cloud of electrons.
Chemical Bonding
Defination of Chemical Bonding: "A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction. The strength of chemical bonds varies considerably; there are "strong bonds" such as covalent or ionic bonds and "weak bonds" such as dipole-dipole interactions, the London dispersion force and hydrogen bonding. " - Wikipedia
Ionic Bonding
So what is an Ionic Bond? When atoms get close together, sometimes they form ionic bonds to make molecules. When those unstable atoms come near another unstable atom, they trade electrons until they find a more stable arrangement. Usually in Ionic Bonding, it is a metal atom joining up with a non-metal atom
For example, some kinds of atoms, like sodium, have only one electron in their outside ring, which is an unstable situation. Sodium's so unstable that if you add water to it, it catches on fire!
When sodium atoms come near chlorine atoms, the chlorine atoms are also very unstable, because chlorine is missing an electron to fill up its outer ring. So when they get together, the sodium atom's extra electron jumps over to the chlorine atom. Then the chlorine atom is stable, and so is the sodium atom.
Covalent Bonding
When two atoms come near each other form bonds to make a molecule, but sometimes they don't form Ionic Bonding, another way of bonding is covalent bonding. Like in Ionic Bonding, in covalent bonding, the atoms are unstable because their outer rings of electrons aren't filled up
By sharing electrons with other atoms, these atoms can fill up their valence shells to gain the electronic configuration of a noble gas and become stable.
In water, for instance, the oxygen atom needs two more electrons to be stable, and the hydrogen atoms each need one. When they get together, the oxygen atom shares one electron with each of the hydrogen atoms, and the hydrogen atoms each share one electron with the oxygen atom.
Now that the atoms have become stable, it's pretty hard to knock them back into being unstable again, so covalent bonds are strong and molecules that form with covalent (sharing) bonds are strong molecules.
Difference between Covalent Bonding and Ionic Bonding
Equation Writing
Equation Writing is like how I would think it as a science sentence. It's as if science had its own language too. It really pique my interest here, on being able to write equations and acting all scientific and "chim" to people who never learnt it before.
Chemical Equations:
Chemical Equations are made up of chemical formulae. A chemical formula is a combination of elemental symbols and subscript numbers that is used to show the composition of a compound. Depending of the type of compound that the formula represents, the information that it provides will vary slightly. Before we went about learning how to write chemical formulas, I knew it was important that I clearly understood the difference between molecular compounds and ionic compounds.
It was a little hard for me at first, trying to remember what are the chemical formulae of each elements, learning how to balance equations, making sense of ions and the different cation and anion. Then I got a hang of it after making sure I studied the textbook thoroughly. To help with my revision, I even found a Chemical Equation Balancer calculator! Here is the link: http://www.webqc.org/balance.php
I once asked my sister, "Why all the 'chim' equations that just make scientists lives harder, making students lives harder, in that we have to memorise and remember all these equations things?" She replied, "Because scientists have to constantly work together, and it is not uncommon to see scientists of different races coming together to work on something. In the case that they do not understand each other's langauge, they would be able to communicate and understand each other's work through chemical equations." I was enlightened, and I was only 7 years old!
Word Equations:
Word equations basically describe chemical reactions using words.
Word equations have the following pattern:
name of reactant 1( ) + name of reactant 2( ) + ... name of product 1( ) + name of product 2( ) + ...
The reactants are the substances with which you begin the reaction. The names of the reactants are listed before the arrow in the word equation. A plus sign is used between the reactants when there is more than one reactant.
The products are the substances made as a result of the reaction. The names of the products are listed after the arrow in the word equation. A plus sign is used between the products when there is more than one product.
Here are some examples:
1. Magnesium metal burns in oxygen gas with a bright white light to make a white powder called magnesium oxide.
magnesium (s) + oxygen (g) magnesium oxide (s) + heat
2. A solution of sodium iodide is added to a solution of potassium nitrate to make a potassium iodide precipitate and a sodium nitrate solution.
sodium iodide (aq) + potassium nitrate (aq) potassium iodide (s) + sodium nitrate (aq)
3. Gaseous hydrogen and gaseous oxygen react explosively to form water vapor.
hydrogen (g) + oxygen (g) water (g) + heat
And that's the end of my first post. I am filled with excitement on all the things that I would be learning on the days and years to come, and Science is always the major factor in it!
