In this video, we're going to learn about the electrical nature of matter. So if you remember, last unit in chemistry, we learned about matter and we learned that matter is anything that has mass and takes up shape. We learned about the structure of the atom and the fact that atoms have positive charges known as protons and negative charges known as electrons. In this unit, we're going to learn about the movement of electrons to create charges on matter.
So making it matter either positively or negatively charged. So static electricity is when a charge on a substance stays in place. So something will become positively charged and stay that way for an extended period of time. And electrostatics is the study of static charges.
I'm pretty sure all of you have experienced the rub a balloon on your head and then trying to stick it somewhere else, you'll find out that the balloon becomes charged, your hair also becomes charged, and then you can put that balloon on a wall and it might stay there. So when an object is negatively charged, there's more negative charges than positive charges on the object. So this is what it would look like.
So you can see here that on this object there's one, two, three, four, five positive charges, but far more negative charges. So this object would be said to be negatively charged. When an object is positively charged, there's more positive charges or protons than negative charges, electrons. So an object would look like this.
So you'd have lots of positive charges here and not so many negative charges. So the positive charges would outnumber the negative charges. A neutral object will have the same number of positive and negative charges, so you would have the equal number. So this is what it would look like.
So right now we're going to talk about the law of electrons. charges, and there are three points. First of all, like charges repel each other.
This means that two negatively charged or two positively charged objects will repel each other. So in this example, we have two positively charged objects, and they are pushing away against each other. And over here, we have two negatively charged objects, and they're pushing away against each other. So they're keeping themselves apart. It reminds me of a...
pair of magnets. So if you've ever tried to put two magnets together, one way they'll attract each other and the other way they'll repel. So when you're trying to put two things together and they're repelling, the magnets are actually trying, you're trying to line them up with the same pole.
So the two north pole magnets will push against each other and two south poles of a magnet will push against each other and repel. So this is very much like that. The second point states that opposite charges attract. So that means a positively charged object will attract a negatively charged one, and vice versa. So if you had something that was positively charged like this one here, it would attract a negatively charged object.
The third point states that a charged object will actually attract a neutral object. So this is what it looks like. A negatively charged thing will attract a neutral, and a positively charged object will attract a neutral object. So we can charge an object three different ways. We can charge by friction, we can charge by contact, and we can charge by induction.
So first of all, charging by friction. This is what happens when two objects are rubbed together. Some negative charges will be pulled from one substance and go to the other, and one of those substances will become positively charged, and the other will become negatively charged.
So an example might be if you were rubbing a rubber balloon on your hair, The rubber balloon could gain negative charges and then your hair would gain positive charges and then they both will become attracted to one another. And that's why your hair will stand up when you bring that charged balloon back towards it. So we can use something known as the electrostatic series to determine which materials will be more likely to hold on to electrons or to give them away. So this is a very small example of the electrostatic series.
So if we look at the top, these objects at the top would have a strong hold on the electrons, so they would be more likely to become negatively charged. So some examples would be Teflon, vinyl, acetate, and rubber. And then gold and platinum are right here in the middle.
We'll talk about that in a minute. And then some objects that have a weaker hold on electrons and more likely to become positively charged are wood, paper, cotton, and then finally wool. There's definitely more and we actually will be spending some time making our own electrostatic series later on this unit.
So if... You rub two objects together, say vinyl and wood, the one that's higher will have the stronger hole in electrons, so it will pull electrons off of the one that's lower. So this vinyl would take electrons from wood, vinyl will become negatively charged and wood will become positively charged. Or you could try rubber and wool or Teflon and paper. So whichever one is higher, it will pull electrons off the lower one and make the lower one positively charged and the higher one negatively charged.
Now gold and platinum are found right in the middle. They are considered to be conductors because they're metals, so they're not as likely to hold on to electrons at all. They'll actually let them pass right through them and go on to another substance. So we can charge an object by contact too, and that's when a charge object is...
touched to a neutral one. And when that happens, that charge is passed on to the other object. So if I walked up to a doorknob and I was positively charged because I've been walking across a carpet and I have positive charges build up on me, if I reach out and touch a doorknob, I will get a shock because I'm charging my contact.
In this example, we'll show how an object can give it half a negative charge on. So if this was our electroscope, this is a pith ball, and we'll be using those a little bit later, and this is some sort of charge object that we're bringing close to it. So if you look here, the charge object has way more negative charges than positive charges, and this pith ball of the electroscope has equal number of positive and negative charges.
So this is what it will look like first of all. Then, if we brought that together and it touched, Some of those negative charges will jump off of the charged object and onto the pith ball, leading to this. So now we have negative charges that have jumped over to the pith ball, and it's now negatively charged. So we've charged that by contact.
In this example, we will show how an object can pass on a positive charge. So if we take a look here, our object that's charged... has a lot of positive charges and only a few negative charges, so it's positively charged. And our other object is neutral.
So when we bring those together, the positively charged object is going to attract the electrons from the neutral object, and they're going to move onto this positively charged object. And then we would end up with a positively charged object from the neutral object. the neutral object has now become positively charged by contact.
Our final form of charging is charging by induction, and this happens when a charged object is brought near to, but doesn't touch a neutral object, and it will cause what is known as an induced charge separation. So the charged object will cause the electrons to move within the uncharged object, and it will induce a temporary opposite charge on the uncharged object. So... an example of this would be with lightning.
So if we had a cloud that had a lot of positive charges built up in this cloud at the bottom of the cloud, it would actually induce a negative charge on the ground below and vice versa. If there were a lot of negative charges in the top part of the cloud, then it would induce a positive charge on the ground below. So it's a temporary degree.
opposite charge that is being induced by just repelling the electrons within the neutral object, and that's charging by induction.