Hi, my name is Thomas Freeman. I'm a STEM, that is Science Technology Engineering and Math lecture in the Department of Chemistry here in UNC. In this video, we will be discussing how chemist think about natural phenomenon, some things you might find a bit shocking or peculiar. Chemistry itself is the study of the properties and changes of matter and energy. To be able to think like a chemist, you must develop a clear perception of the nature of modern energy as we know it. In order to do that, we're going to take a closer look at the particle that a chemist consider to be the quiet essential building block of all matter, the atom. Most atoms are made up of three types of sub atomic particles, it is in the center of the atom, the nucleus. We have the positively charged particles called protons, and the uncharged particles called neutrons. These are very large particles relative to the third type of particle, and they make the majority of the mass of the atom, the third particle is the electron, okay. This makes up the exterior of the atom, and even if there are, there are few electrons around the atom. They move about the entire nucleus of the atom so fast, that they look like basically a cloud. Okay, so just want to electron look like a cloud around an atom. How small is this atom that we're talking about? It's pretty tiny, if you look at the scale of the universe, humans are a 10 to the 0 meters, that is the one meter scale. And as we scale down we can see that there are lots of tiny objects much smaller than us. Insects, white blood cells, bacteria, viruses, proteins, DNA, and on and on, and on. And if we keep going way, way down in the scale, we finally reach the nucleus of the atom, it's a 10^-15 meters. That means that the nucleus of the atom is 15 orders of magnitude smaller than humans. A human is 1 quadrillion times larger than an individual atomic nucleus but also means that we are made up of atoms. So, if the nucleus is 1 quadrillion times smaller than us, what do you think is 1 quadrillion or 15 orders of magnitude larger than us? Now, let's take a look at what's actually out there, what's 15 orders of magnitude larger than us? Is it a planet? No, not so much, is it the sun? A star, right? Or maybe a larger star than the sun? Nope, not even those are a 15 orders of magnitude larger than us. We have to go way out until we get to Nebula, these large clouds of dust and gas. Now with that a mind, do you think the nucleus had a consciousness is we do. That it would know that was part of a living organism that with 1 quadrillion times larger than itself. I think not unless it had a really good telescope. So how do you know that you are not part of a living organism a quadrillion time bigger than you? [MUSIC] Another thing about matter that you ought to understand is that, according to scientific law, matter is conserved, that is, it can neither be created nor destroyed. For example, if you burn a fuel like methane, CH4 as we symbolize it, this is natural gas. We use it to heat our homes and to cook our food. And in the presence of oxygen, all molecules of methane are transformed into an equal mass of carbon dioxide, that is CO2, and water, H20. It's just that the connections between those atoms are rearranged, all right? We don't lose any mass at all, we keep the exact same number of atoms, the same types of atoms, they're just connected to each other in different ways. And we also keep the exact same mass that we started with. Now armed with that idea of conservation of matter, see if you can figure out how heavy this atom of helium is. [MUSIC] Now if you were thinking about this the way I expected you to, perhaps you took the proton's mass and doubled it and added it to the neutron's mass that you doubled as well, right? So two times the proton mass, two times the neutron mass to get the total mass of the nucleus of helium. And you probably got A as your answer. However, when scientists measure they're mass of helium, the whole atom, they actually give bit, 4.00260 amu. That's not a huge difference but it is significant difference between the two masses, how was that possible. How is it that you can add these four particles together, and end up with a mass that's less than the total sum of the masses of the particles themselves? There's a little bit of magic to this or maybe it's not magic, maybe it's just science. The mass is less because when binding happens between subatomic particles, some of the mass is converted into energy. And then that energy is released into the universe, who figured this out? Einstein did and you probably already know the equation that's used to describe how this phenomena works, E=mc squared. That is energy is equal to the mass times the speed of light squared, this means that matter and energy can actually be interconverted. In fact, you can look at matter as simply a storage vessel for energy. And this is why chemistry is about better understanding the changes in matter and energy.
