2009 29 July Chemistry Chemical Changes Post ONE Hey! Long time no see! Okay, because of the deadline and me being down with flu this few days, bear with me, I might have to post two to three post in a day. Alright, I thought this year the Chemistry topics were hard to choose from. Now, let's start. Here's the rough skeleton I will be following, and it is not confirmed yet, will tell you guys when its confirmed.
I am sad, and sorry to say, that this time, each post would not be very long, in fact, it would be quite short. About two to three paragraphs. Now, I will begin. Again, before we start, here's a nice and short clip for all of you to enjoy and will sure help you understand more about Physical and Chemical Changes. Do take some time to watch it. As you might have seen from the video already, there are differences between Physical and Chemical Changes. A physical change is whereby a matter or substance changes physically, meaning that it can change its state it is in (solid, liquid, gas, plasma) or it can change its size or shape, however, the substance that makes up the object, does not change. For example, you can take a piece of paper and cut it up into small squares, it will still remain as paper. Hence, that is physical change. Or, you can take a cube of ice and melt it, just because water changes from a solid form to a liquid form, it doesn't mean its a Chemical Change, because nothing in the substance is changed, as water still remains as water, except in a different form. Hence, that, is also Physical Change. One important thing about Physical Change is that it can be reversed. After melting ice to become water, you can then cool it to make it into an ice cube again! However, Chemical Changes are different. Firstly, a Chemical Change is where there is a Chemical Reaction. The substances in the matter is changed during Chemical Change. Chemical Change can form a new substance, and most importantly, during Chemical Change, energy is either given off or absorbed. If you would to take a piece of paper and burn it, it would be Chemical Change, as a new type of substance is produced, and of course, Chemical Changes cannot be reversed, even if it could, it would take extraordinary means to do it. For example, if you fry an egg, it would be very hard, or even impossible to "un-fry" it. During Chemical Changes, heat is either lost or gained. If heat is lost, we call it an exothermic reaction. If heat is gained, we call it an endothermic reaction. The temperature pressure and substance involved in the change (or reaction) will affect the speed which at the change (or reaction) takes place. Previously, I did mention that Chemical Changes is where there is a Chemical Reaction, so, I will be zooming on to the topic of Chemical Reaction now. Again, I would like you all to watch a few videos about Chemical Reactions. So what exactly is happening in the videos above? Well, Chemical Reaction! However, in Chemical Reactions, there are five major types of Chemical Reactions, namely Synthesis, Decomposition, Single Displacement, Double Displacement and finally we have Combustion. And I will talk more about these in the next few posts. With this, I will end this post. Link One Link Two Glossary Physical The outer surface of something, normally able to be able to observe. Substance Something which has mass and occupies space. Exothermic A compound formed with the liberation of heat. Endothermic A compound formed with a absorbtion of heat. |
By Zhan Peng from 2-6 Catholic High School Class 2-6 One Golden Rule NOTHING |