[Music] hi it's Mr Anderson and today I'm going to be talking about changes um these changes are physical and chemical changes and uh students sometimes struggle telling the difference between chemical and physical changes and teachers love to kind of ask you hard questions like uh let's see if if water is boiling is that a physical or a chemical change or if a moth ball vaporizes over years is that a physical or a chemical change or if you mix vinegar and baking soda is that a physical or a chemical change so hopefully by the end I'll give you a few Clues that'll allow you to answer that um this picture I I decided to start with this picture right here um I live in Montana and so in Montana the burgers that we have are are pretty good the steak that we have is really good in Montana but we don't have In-N-Out burger and whenever I go to California I love to get a nice In-N-Out Burger uh cuz the fries are perfect get a shake oh my goodness I'm already getting hungry um but when I eat that burger that burger is going to go through two changes the first changes it's going to go through are physical in other words I'm going to start chewing up that burger and making it into smaller little bits and then it's going to go through my digestive system and I'm going to start to chemically break down that burger now the cool thing about um about a burger is that that burger will eventually become you in other words the amino acids that are in a burger are going to be broken down and then they're going to use them up inside our body to actually build up the proteins inside our body and so it's important that you understand uh chemical and physical changes and the difference between them because you need to understand how you are made from a burger okay so let's get started let's start with physical changes my definition for physical changes occur when the appearance changes but the substance does not and so if we were to look at this pen for example is it under undergoing change we'd say no it's not changing at all but let's say that this pen were to change its appearance but it were still to be the parts of a pen that would be a physical change and so how could that happen well if we were to heat this pen up and so it were to melt slightly it still would be a pen if we were to break it in half or bend it it would still be a pen in other words as long as it doesn't combine with another chemical as long as that substance stays the same it's a physical change in other words if you start with something like water and we go from water that is a solid like in this um down here and then we end up with water that it is a let's say a liquid in other words it starts to melt or even if it's H2O that forms a gas a lot of this H2O inside this ice is actually going to sublimate so it's going to vaporize and turn into a gas well it's still H2O and so it's going to be a physical change at each of those points and so here are some things on the side that I said you could check off if it's a physical change if it's just melting if it's boiling and so I think I have a picture of that so for boiling water this always blew me away as a teacher um a lot of people don't know why water boils in other words they say okay you heat it up and it's going to boil but they don't know what's inside the bubbles inside boiling water and so what is inside the bubbles inside boiling water well it's not hydrogen and oxygen gas that'd be bad because if it was hydrogen and oxygen gas hydrogen and oxygen gas once they come out would quickly combust hydrogen is going to combust and explode and we know that doesn't happen and so what's actually in the bubbles in boiling water it's simply water vapor in other words it's water that is in the state of a gas and so we would say not a chemical change that's a physical change or if we were to for example break these bricks in half or keep breaking these bricks in half and half and half and half and half and they're still bricks then we call that physical or let's say we were to cut things in half so if we were to use this torch and to cut this metal in half the metal here and the metal here would still be the same and so we call that a physical change to this pipe now right along the point at which you're cutting if we combine that with oxygen right along that edge then it's going to be oxidized and so we call that a chemical change and then another tricky one that science teachers like to trick you up with is dissolving so if in other words if I were to take uh a little bit of sugar and add it to this tea as that Sugar dissolves in other words as it goes from this solid to more um surrounded by water kind of a state we wouldn't call that a chemical change we call that a physical change and so it's not a chemical change and if it's physical change then we don't have any kind of a chemical reaction taking place and we don't have a formula we simply have a change in its state or change in its appearance and so there's a lot of stuff that's not really a a chemical change so let's get to what a chemical change actually is chemical change is when you have a substance that changes and so for example if we go back to water again if I were to break down water into its gases H2 and O2 then you'd know that I not I don't have a water anymore I have a hydrogen gas and I have oxygen gas and so we'd know that a chemical change has occurred in other words the substance on one side yields that's what the sign means yields two new substances on the right and these would be the products over here and so we'd say a chemical change has occurred now what are some clues that tell us a chemical change has occurred uh maybe it produces Bubbles and so this right here is uh mixing acetic acid um with sodium bicarbonate otherwise known as mixing baking soda with vinegar and what we're getting is Bubbles forming and those bubbles are going to be a new gas now you might be confused thinking yeah but you just talked about boiling water and how once that turns into bubbles then it's a physical change well think about it did we have bubbles inside the vinegar did we have bubbles inside the sodium bicarbonate no and so we've created something new we've created a gas and that's what's actually forming the bubbles and that's what makes the volcano explode when you did this in in elementary let's say we mix two chemicals together so we've got chemical a and chemical B and we mix one chemical and the other one which normally was cleared starts to get kind of Cloudy so we'd say a chemical change is probably occurring if we ever have a a clouds showing up either cloud liquid or clouds in the air that usually just means a new particle is being formed and so new chemical is being formed okay let's say we get a temperature change a temperature change is going to indicate a chemical reaction is taking place and so the simplest one would be like in methane methane is natural gas it's in AB bunson burner and so when we combine that with oxygen O2 gas we get some carbon dioxide we get some H2O and we get a lot of energy and so we're creating energy or giving off energy that was stored in the chemical bonds of the methane and so we would call that a chemical change in other words we've increased the temperature um so this right here is pretty cool we've got two different salts that are probably burning in alcohol and they're giving off colors depending on what kind of atoms they are um and we would call that a temperature change the salts by themselves are white um and then as we add enough energy you get combustion with the oxygen and so this is how fireworks are formed we have have salts that are mixed up and then they we give them combustion or or enough of an oxidizer and we can get all these different colors so a color change would indicate that we've got a chemical change going on and then the last one that would indicate that we've got a change is if we've got oh here's a cool one this is bioluminesence and so this is adding a couple of chemicals that actually glow um and so we see this in life a lot for example we have jellyfish that can produce this glowing protein um so that's chemical reaction we're mixing chemical and giving off light and the last one that I was trying to get to um is is bread if you've ever smelled baking bread there is a chemical change that's going on inside the bread so all the products by themselves didn't smell that way but we mix them together we get chemical reactions going on and so we've got a smell or a change in state now tasting bread is totally safe but tasting chemicals in the lab is not so safe and so I would steer clear of that uh this would be a sparkler and so what do you think chemical change physical change yeah that'd be chemical or going back to a couple of those answers at the beginning that I posed what about boiling water chemical or physical right answer would be physical or what about taking moth balls that you put in in your drawer to keep your sweaters the moths off from eating your sweaters if that vaporizes over time what that's going to be it's going to be a physical change okay and so the last thing I want to leave you with is if we ever have a chemical change then we have a chemical reaction and so in a chemical reaction you're taking these things which are the reactants this would be the first reactant the second reactant and then we're making products from that so if we mix hydrogen gas with oxygen gas and create water then we've had a chemical change and we usually have to add a little bit of energy to that now you should know this the reactants are on the left side the products are on the right side and this Arrow stands for the word yields and so if I to sketch this out for a second let's do hydrogen hydrogen is going to look like this hydrogen Is two hydrogen molecules attached together and so this two right here this is called the subscript that tells me that there are two atoms of hydrogen in a molecule of hydrogen um this two in the front means that we have two molecules of that and so on the left side we've got two molecules of hydrogen uh gas on the side but each of those molecules are made up of two atoms of hydrogen if we look over here at the oxygen o oxgen I'll draw that a little bit bigger oxygen attached to itself there's two oxygen atoms but there's only one molecule of that and so now let's look at the product well if we look at the product over here on the right side we're going to have one water so water looks like this it's got a hydrogen and a hydrogen it's got another water here hydrogen hydrogen and so if we count them up we should have the same if it's a balanced equation so how many hydrogens do I have on the left side one 1 2 3 4 how many hydrogens do I have on the right side 1 2 3 4 so that's balanced if you're look at the Oxygen's on the left side we've got one two on the Oxygen's on the right side we've got one two and so that's a balanced equation and so I've got a podcast on balancing equations you can take a look at if you don't know how to do that the key thing is that you can always change the coefficients this would be a one right here you can always change what comes before the formula but you can never change the subscripts because if you're changing the subscripts it'd be like breaking that oxygen a half and we know that that doesn't occur so I hope that's helpful those are chemical and physical changes