2009 4 August Chemistry Chemical Changes Post FIVE Okay, this is the FINAL AND OFFICIAL POST!
I shall start with Covalent Bonding. Firstly, I will be showing you two self-drawn pictures.   In the first picture, we can see that the hydrogen atoms only have one electron, and the valence electron value for hydrogen is 2. However, we see two hydrogen, and each of them are trying to attract the other hydrogen's electron. However, if one does attract it, one hydrogen would have no electron (impossible), hence, they share a covalent bond, and inside that covalent bond, there are 2 shared electrons, 1 for each hydrogen, hence, each hydrogen would have 2 electrons. Sometimes, there are multiple bonds.   Instead of sharing a bond to complete the valence electron of 6, there share multiple bonds. The diagrams I have used above is called the Lewis Dot Structure. Here, I have come to the end of my BioChem Journal, here is the reflection for the Chemistry Journal. During the course of my research, I believe that everything that I have come across is interesting. During the course of the research, I have learnt a lot of new things, and many things surprise me. Also, not only did the information that I have gained surprised me a lot, I have also learnt a lot of new stuff. All of these information surprises me as before I carried on with this research, I did not know that things work that way. Of course, after the research, there are still many things left unanswered. The world is so big and there are so many scientific knowledge. Some queries would be examples of chemical reaction, for example, mixing chlorine and sodium, what causes the spark and how do people produce table salt in mass quantities. Also, I would also be interested to find out how chemical reactions can help the world evolve, or how has it already helped the world to evolve at the current stage it is now. This time, the difficulties faced are much greater than the ones faced when doing the Biology Blog, this is so as during the course of the research, the common mastery reviews are also nearing by, and national day parade is also coming, hence, there is less time for us to do our research and in turn, do our blog posts. Hence, we have to learn to manage our time wisely, also, the topics given were hard as we have not started learning them yet, so we had to pre-learn some things before it was taught in class, if not, there would not be enough time. My personal response would be that I was really shocked and I learnt a lot of things about Chemical Changes, Chemical Reactions and of course, bonding. I have also learnt applications of Chemical Reactions, and elements, most importantly, like how carbon is compressed under high pressure to make diamond, how copper is bent to make wires, how graphite is used as the lead of our pencil cases, how silver is malleable and ductile and bent to made jewelery which we wear today, etc. And yes, it has influence me, I have started to look at the world in a different perspective. Sometimes, I wonder how is everything made, how is our computer made, and I have become more curious. I also want to find out more about this topic, and hope that my research continues. Also, this has also urged me, if I have the chance next time, to go explore factories and observe the different processes in the factories, what type of chemical reactions they use, what elements do they mix in order to form everyday materials that we find. Also, after the course of this research, it has urged me to regularly check the periodic table for any new elements discovered, and keep up to date with any changes in the atomic number, or the positioning of the elements. Lastly, I hope that I can still continue posting on my BioChem Journal Blog. There will still be 2 more posts, Fun and Interesting Facts on both the Nutrient Cycle and Chemical Changes, so do check back often. Also, I hope to continue the blog, and I will be posting about interesting scientific stuff I have seen in my life. So, bye! Link One Glossary Electrons Positively-charged atoms 2009 2 August Chemistry Chemical Changes Post FOUR
Hey guys! Made some changes to the skeleton, and I can confirm that this will be the final skeleton I'm following. I added in an Introduction to Elements, as I thought it would be important for you guys to understand more about elements before we continue on. Also, I removed Metallic Bonding, although my topic is on Chemical Changes, I did not want to dwell too much on bonding, hence, I removed part of it. Without further ado, I shall begin. C6H12O6 This is the chemical symbol for glucose, or sugar in this case. As we can see, it is made up of C (carbon), H (hydrogen) and O (oxygen). Imagine if all these were separated, what would you get? You would get something that cannot be broken down into simpler substance by chemical reaction, and THAT, is an element. Hence, element is defined as a substance which cannot be broken down into simpler substances by chemical reactions. Hence, it is the building block of matter. Another example would be water during electrolysis. It breaks down down into Hydrogen and Oxygen. Hence, Hydrogen and Oxygen are elements. We use Chemical Symbols to represent some elements. Most of the elements come from the first letter, for example, Hydrogen's Chemical Symbol is H. Some comes from the first two letters of the Chemical. However, every letter that follows the first letter must be in small letter. For example Aluminium is written as Al. Sometimes, not the first two letters are used, Chlorine is written as Cl for example. Others come from other language like latin, example would be Tungsten, which is written as W. Elements can be classified into two different types. Metals and non-metals, we will talk more about that later. Some examples of metals would be mercury, tin or aluminium. While non-metals would consist of chlorine, bromine, sulphur or iodine. Metals are normally shiny and have high density, they also have hgih melting and boiling points. It can conduct electricty and heat well, and is normally ductile and malleable. There are many different uses of elements, for example, carbon can be compressed under high pressure to form diamonds. Nitrogen can be formed into liquid form to keep things cool. Mercury can be fit inside a thermometer to measure temperature. Or carbon can be made into graphite which is what we use in pencil lead. With this, I will move on to ionic bonding. As I have said earlier, sodium metal combines with chlorine gas to form table salt. In this bonding, sodium loses one electron to the chlorine gas, and chlorine will complete its valence electrons and it will become 8 electrons.   And that is basically ionic bonding. Also note that after the bonding, the sodium turns into a negative-charged ion andd the chlorine gas turns into a positive-charged ions. With that, I end this post. In the final post, I will talking more about Covalent Bonding. Link One Glossary Electrolysis Using electricity to drive a chemical reaction. Ductile Able to be easily bent. Mallaeble Can beaten into shapes. 2009 1 August Chemistry Chemical Changes Post THREE
Alright! Good! We're coming to the last two section of the Five Major Chemical Reaction! So let's not delay! Also called Single Displacement, Single Subsitution or Activity Replacement. Single Replacement, as the name suggests, is basically one component of a compound "going" to the other. For example, if we place a piece of copper into a silver nitrate solution, slowly, you would see that the copper begins to turn into a silvery-white material, and the solution begins to turn from light silver into blue. What is actually happening is that the silver from the silver nitrate solution is "going" to the copper, hence, we can represent Single Replacement with a simple equation. AB and C -> A and CB Or in the previous case, the copper and silver nitrate solution can be represented like this. 2 AgNO3 + Cu -> Cu(NO3)2 + 2 Ag There are two types of Single Replacement, mainly cationic and anionic Single Replacements. In an cationic Single Replacement, ions are produced, while in an anionic Single Replacement, ions are not produced. The above reaction would be considered cationic as it is likely to make cations. An example of anionic reaction would be bubbling chlorine gas in a potassium iodine solution, the chlorine is used up and the solution turns purple-brown because of the iodine. Also represented as, 2 KI + Cl2 -> 2 KCl + I2 Now that we have finished Single Displacement, I will move on to Double Displacement. As we have said just now, Single Displacement is the component of a compound "going" to another compound or element, in Double Displacement (also called Double Replacement or Metathesis), instead of "going" to the other compound or element, it switches place with another component of the other compound. One common example would be hydrochloric acid (acid) and sodium hydroxide (base) would neutralize each other (as one is acidic and one is alkaline) to make water and salt. This can be written in this way. HCl + NaOH -> HOH + NaCl Hence, we can simply write Double Displacement as... AB and CD -> AD and CB Now that we have finished all five major chemical reactions, you might be wondering, how can some of this happen? One major thing would be bonding. And that is what we are moving on to next. Have you ever wondered even though the Periodic Table only has 118 elements, why are there so many we see in our everyday life? This is so as the elements can bond together to make other elements. So in this case, why do bonding happen? And how does bonding occurs? It is said that atoms with less than 8 valence electrons will bond together with other atoms to "complete" the full 8 valence electrons. In the periodic table, different groups of metal are classified according to their different valence electrons. Group One has 1 Valence Electron. Group Two has 2 Valence Electron. Groups Three to Twelve have Electrons that are normally not easy to count with the orginial way. Group Thirteen has 3 Valence Electons. Group Fourteen has 4. Group Fiveteen has 5. Group Sixteen has 6. Group Seventeen has 7. Group Eighteen has 8 or 2. (in the case of Helium, it is 2) An simple bond would be between sodium and chlorine gas, which would result in the table salt of what we have now. So how is bonding done? Well, it is exactly the same as magnets. The negatively charged electrons would attract the positively charged protons, and it completes the bond this way. A amount of energy or heat is needed to separate these bonds. Now that I have come to the end of the introduction to Bonding, we will be talking more about elements, and of course, the two different types of bonding I am going to touch on would be Ionic Bonding and Covalent Bonding. Link One Link Two Link Three Glossary Cation A positively-charged ion. Valence Electron The number of electrons on the outmost shell of a certain element. |
By Zhan Peng from 2-6 Catholic High School Class 2-6 One Golden Rule NOTHING |