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Chemical Equations - Concept

Teacher/Instructor Kendal Orenstein
Kendal Orenstein

Rutger's University
M.Ed., Columbia Teachers College

Kendal founded an academic coaching company in Washington D.C. and teaches in local area schools. In her spare time she loves to explore new places.

A chemical equation shows the reactants and the products of a chemical reaction. Balancing chemical equations is necessary because the same atoms should be present before and after the reaction, just in different arrangements. A balanced chemical equation is useful in showing us the ratios of reactants and products.

Alright so let's talk about chemical equations. Alright so in a chemical reaction how do you know if a process takes place, how do you know if it's a chemical reaction or not? Well the main thing, one of the main ideas if it happened or it didn't is it can't get back to original state. That's a pretty good question you can ask yourself like if something happens can I get back to where I was originally to see if it was actually a chemical reaction. There are 4 main indicators that the chemical reaction actually took place. Bubbling is one of them, so when you have, when you put 2 things together and bubbling starts to occur that's a gas being formed, so those bubbles there's actually a gas. So when you have bubbling you're actually forming new gas particles.

Another thing is color change. If you think about let's say in the fall the leaves change color, that's an actual chemical reaction that takes place. So something that changes color you put 2 things together and it turns from like pink to like blue that's a good indicator that something happened, there's a chemical change there. Also another one is the release of energy that can be in the form of light or heat. Any of those things like when you burn something that is a good idea of that a chemical reaction took place it could really be some sort of energy it doesn't matter if it's thermal, doesn't matter if it's kinetic one of those things any type of energy that you're going to release is definitely a good indicator. Also the formation of precipitate now it's probably something you probably haven't heard. Precipitate is when you have 2 liquids and you put them together and you get like a solidity, a solid material that comes out of it. So it can look like a little flakes of a solid, that's a precipitate. You might have, do a lab class so you form precipitates.

This is actually just making, it might look like just a color change but they're actually like a solid within a solution or a water solution, so in order to indicate that a chemical reaction took place, you're going to write it something that looks similar to this, this is obviously the simplistic form you're going to have. You're going to have on your beginning things you're going to have are called the reactants. These are guys that are going to react together. And then we're going to say the arrow which indicates, okay they're going to go from the reactants to something else. They're going to change form and to actually say that out loud you're going to be use the word yield. Like reactants yield the products that's a new Chemistry term for you.

And then the products at the end are molecules you're going to end up with. Alright so let's do something together, okay so over here we have a written reaction rxn is my little short hand for reaction so we have solid zinc, so how do we write that out? We're going to say just write the element zinc and I had to indicate that as a solid because that's important. So next to it I'm going to put in parenthesis and s to indicate that's a solid [state of matter] and aqueous hydrogen sulphate so because I'm putting them together I'm going to put a little addition sign that shows that these 2 are coming together. Aqueous that's important we'll get to that in just a second. Hydrogen sulphate okay so sulphate we know is a sulphor minus 2 hydrogen, it's hydrogen plus, we're going to do our sawpping, this is a plus 1, so it's going to be H2SO4 we need 2 hydrogens and 1 sulphate. We have to make sure that we show that it's aqueous meaning that it's in solution so it's in a water solution, so we're going to put a little aq to say it's a solution of this material reacts in order to see how these things are going to react I'm going to put my arrow yield to produce something new hydrogen gas and like a hydrogen is one of our diatomics don't forget our diatomic is [sprinkle half] I know you've heard of [sprinkle half] but bromine cannot stand alone, chlorine cannot stand alone, iodine cannot stand alone, hydrogen, oxygen and fluorine.

These elements you'll never see them by themselves ever, ever, ever so whenever you see hydrogen gas for example you're going to have, it's going to be H2 okay and it's a gas so we're going to indicate that by lower case g and aqueous zinc sulphate, zinc is a plus 2, sulphate is a minus 2. So we're going to say zinc sulphate okay and this is aqueous so we have to indicate that as well meaning that it's in it in solution so we're going to put the little aq. So we have to make sure we put our state of matter solid is s, liquid is l obviously gas is a g and if it's in solution I know this is the matter that we're used to we have to make sure we have, if it's in solution it's called aqueous and we're going to say aq. So this is what we're going to call skeletal equation we have to go further on to balance this and we're not quite finished with it yet but this is how you go from, to make a written solution sorry written reaction into an actual skeletal equation.