Physical Changes All About Us

hi every buddy here I am on my way to the lake to get a load of sand in my trusty egg carton and here I come okay but remember I'm going to do the talking you better tell mom you're going she knows while you're riding you can think about what I'm going to talk about matter matter you know things all around us like slides and Kites and sidewalks and benches in rain that helps trees grow and air that kites fly on those are funny things to think about why should anybody want to because those things will help everybody think about the different states of matter they sure think about wood wood is matter in the solid state you see Bing oh sure I see and water it's a liquid water is matter in the liquid state and the air that's all around us air is a gas air is matter and the gas State I can't see it but I can feel it when I wave my hand I can kind of feel it too okay now since you know the three states of matter solid liquid and gas we can talk about some ways matter can change you want to finish squashing this can okay do you know what this shows what that the size or shape of matter can be changed is that what this shows oh be quiet and come on I want to show everybody something else you know what my sister's drippy popsicle shows that the state of matter can change solids can change to liquids and liquids can change to gases and matter can change the other way too that's because matter is made of very small parts called BL no molecules a solid Like a Rock has a shape a solid keeps it shape and size unless something changes it solid things have shapes that's because in a solid the molecules are very close together and don't move around very much something like this when molecules are very close they have a strong attraction for each other you mean they hold on to each other kind of and that means that a solid keeps its shape unless something changes it but molecules in a liquid don't attract each other as much so a liquid takes the shape of whatever it's in liquids take the shape of their container oh in a liquid molecules have more energy than they do in a solid and they go faster too they bump and move around a lot they spread out to the sides of their container and settle to the bottom too and gravity gives the liquid a smooth top surface but even though liquids don't have a certain shape they do take up a certain amount of space a little water will fill a little space and a lot of water will fill a lot of space what's the unusual about that well that isn't the way it is with the gas when you blow into a balloon you're blowing air in air is a gas as soon as you blow any air in molecules of air go everywhere in the balloon well that's the way it is with all gases gases fill up whatever they're in how come let me let go of the balloon first and then I'll show you okay it's because of molecules again molecules in a gas have lots of energy they move in all directions until they bump into something and then they bounce off that's how they fill the whole container they're in even when you let some gas out of a container the molecules that are left in still fill it you think the balloon will be empty soon won't it be nope it'll still be full of molecules of air and because gas molecules have so much empty space between them we usually can't see gases is that why air is invisible that's why that's very interesting you sure know a lot about man I especially like the part where a solid changes into a liquid oh you little oh you made me forget my egg carton wait till I catch you while my daughters are busy chasing each other I'm going to make a physical change in a piece of wood a change in size is a physical change in matter the molecules of the wood aren't changing I'm just sort of chewing some of them out with a saw to separate the board into two pieces molecules in a solid attract each other so it takes energy to saw through wood but it takes even more energy to saw through metal the parts of a metal are attracted to each other even more strongly the kind of energy I'm using to do this work is called mechanical energy I have to use enough energy to overcome the force that holds the metal together and I did the physical change I'm going to cause will make something get bigger instead of smaller and I'll use a different kind of energy to do it than the girl's father did this is something I use usually do for my science classes it's a good demonstration see how easily the metal ball falls through the Ring of course that's because the ring is bigger than the ball but I'm going to change that it's not a trick I'll do it simply by using heat energy I'm going to make a physical change in the ball the flame heats the metal ball when the metal is heated what do you think will happen the ball became too large to go through the ring heat makes metal expand heat makes most substances expand that's another physical change and that's the end of my part of the story for now do you think you can behave I'll try because there's something else I want to show you about how heat makes metal expand and POS phys pain I can't hear you I said I want to tell something else about heat making metal expand what's bad sometimes things are built so that they can expand without causing any problems like what kind of things like railroad tracks for instance they're made of long pieces of metal you know do you think the pieces are put right up against each other no that's right see there's a space between the rails so they can expand when they get hot that's cool I'm back again and I'm going to show you another kind of physical change that happens to things when they get hot this is a piece of solid lead that I'm heating do you know why the lead is dripping where it's being heated it's dripping because it's melting it's changing to a liquid the lead is changing state from the solid state to the liquid state change of state is another kind of physical change the liquid lead is dropping into a dish but do you think the dish is filling up with liquid lead no the liquid lead is Cooling and changing back to solid lead if you make most solids hot enough they'll turn to liquids if you cool them enough they'll change to solids and if you think that's interesting I've got something else to show you this will help you understand why changes in state take place these things aren't hot they're very cold we call this dry ice but these are really chunks of solid carbon dioxide carbon dioxide is usually a gas but when it's cold enough it's a solid now I'm pouring in some alcohol the alcohol will get very cold much colder than water when it freezes now I'm floating an ice tray in the alcohol and I'm going to pour some water into the ice tray can you guess what's going to happen to the water if you think it's going to freeze you're right that'll take a little time but lucky you you're going to get to see it happen and speed it up motion ready the water's freezing do you know why coold does that to water because as the water cools off its molecules slow down attract each other more and arrange themselves in certain positions a change of state takes place liquid water becomes solid ice when water boils its molecules move so fast it changes to a gas I see it what's that ice cube tray for that'll help me tell you about water in the gases state water vapor the bottom of the tray is getting wet but where's the water coming from from the water vapor the cold ice cube tray cools the water vapor and changes it to tiny drops of liquid water the air cooled the hot water vapor and it changed State now I want to talk about another kind of physical change suppose some lemonade I make tastes too sour what should I do about it oh you know put sugar in it oh you're so smart but where's the physical change just wait a minute till I get the sugar now the physical change I'm talking about happens when some solids are mixed with some liquids like when sugar is mixed with lemonade let me put in some sugar and we'll see what happens the solid sugar seems to disappear into the liquid it dissolves dissolving is a physical change the molecules of the sugar fit in among the molecules of the lemonade which is mainly water when a solid is dissolved in a liquid we call it a solution is your solution sweet enough I'll see yes it is now you can make a solid come out of the solution by letting the liquid it in change to a gas you can let the liquid evaporate or heat it to speed up the evaporation and then you get the sugar back some of that sugar on the inside of the glass physical changes like the one you just saw are used to get the salt out of Salty Sea water and turn it into fresh water that's what I'm doing here I'm boiling sea water with salt dissolved in it the heat changes the liquid water into water vapor but there isn't enough heat to do anything to the Salt that's dissolved in the water the salt stays behind the hot water vapor cools when it goes into the glass tubes and changes state it becomes a liquid water without salt fresh water and when all that water has evaporated what do you think will be [Applause] left no more solution just salt with the water gone the salt that was dissolved the solid salt again and it doesn't look like salt but it is people can use salt from seawater sea salt is just sea water without the water now I'll use the sand I got at the beach what are you making the sand I already made them molds for candles you're making candle yep with the help of physical changes of course come on really see I'm shaving off pieces from big chunks of wax remember a change in shape is a physical change oh sure that's right and the next thing I'm going to do is a physical change change too it is sure I'm going to melt the shavings when solid wax changes to liquid wax that's a physical change hey I can smell a hot wax sure a little changes into a gas that fills the room that's what you smell and now the liquid wax will take the shape of the mold I made see I see and for when the liquid wax cools and it changes to a solid it'll keep its shape like this one did isn't that neat it sure is physical changes are really useful they sure are now I'll review what they are let me do it sure go ahead well physical changes are changes in size or shape or the state of things or when things dissolve and make Solutions or come out of solutions right right right you're a smart little sister you're not so bad a big sister either haven't I always told you that