in this video we're going to talk about the difference between a physical change and a chemical change when a physical change occurs the chemical identity Remains the Same you still have the same substance but when you have a chemical change the chemical identity of the substance actually changes you have a new chemical formula now let's say if you have a piece of paper and you crumple it is that a physical change or a chemical change crumpling paper is a physical change it's still paper the substance is still the same you haven't changed the identity of the substance so that makes it a physical change now let's say if you were to uh burn paper if you took a lighter and you burn paper the paper will eventually disappear it will turn into carbon dioxide and water vapor so in this case the the chemical identity of the paper is changing it's changing into a new substance into water and carbon dioxide so burning paper is a chemical change now what about freezing is freezing a physical change or a chemical change so if you take liquid water and you put it inside your freezer and then it turns into ice what type of change occurred is it physical or chemical freezing is a physical change freezing takes a liquid and converts it into a solid any type of change in a state of matter is a physical change ice is still water it's just water in its solid form so the chemical identity has remained the same liquid water has the formula H2O ice still has the formula H2O so you haven't really change the chemical identity of the substance so if the chemical identity of the substance is still the same then the only change that could have occurred is the physical change not a chemical one now let's say if you take water and you add electricity to it and it breaks down into hydrogen gas and oxygen gas is that a chemical change the electris of water is a chemical change if you can break it down into its elements then the chemical identity has changed hydrogen gas behaves completely different than liquid water oxygen gas is completely different than water it's a whole new chemical substance and so when you get a new substance from another substance that's a chemical change now what about burning gasoline let's say as you drive your car you're burning gasoline is that a physical change or a chemical change gasoline is basically a mixture of hydrocarbons and when gasoline reacts with oxygen in air it creates carbon dioxide and water in a combustion reaction so therefore the chemical identity of the substance is changing gasoline when after reaction with air turns into water vapor and carbon dioxide which is a completely different substance than gasoline so that's a chemical change the chemical identity is changing you can see that in the new formula that's being uh presented so anytime something is burning if you burn paper if you burn gasoline if you burn wood all of those are chemical changes you no longer have wood once you burn it it's in the air it's CO2 and water now what about when iron metal rusts when it corrodes and form iron oxide is that a physical change or a chemical change any type of corrosion is a chemical change when iron metal rusts it reacts with oxygen and it turns into iron oxide so iron oxide and iron are completely uh different substances iron oxide might be that orange red rust that you see around iron metal on the outside iron metal conducts electricity iron oxide does not so it's a whole new substance which makes it a chemical change so any type of burning process any corrosive process that's a chemical change so any time something is reacting if there is a chemical reaction it will lead to a chemical change now what about boiling let's say if you boil liquid water into steam is that a physical change or a chemical change boiling converts a liquid into a gas steam is still H2O it's still water so that's a physical change another example of a physical change is melting melting is the opposite process of freezing melting will take a solid and convert it to a liquid so when ice melts into liquid water that's a physical change all you got to do is add heat to ice and it's going to melt into liquid water now let's say if you have a beaker and there's a red solution inside the beaker and let's say in the course of 30 seconds or a minute the color of the solution changes is this a physical change or a chemical change in chemistry whenever you see the color of a solution changes it's because there's some sort sort of chemical reaction that's occurring and therefore a color change is associated with a chemical change something is reacting and when something reacts chemically speaking the chemical identity changes so a color change is usually accompanied by a chemical change now let me get rid of a few things now what about vaporization is that a physical change or a chemical change vaporization is the process that occurs when a liquid turns into a gas which is like boiling if you boil water and you turn it into steam you're basically vaporizing water that's a physical change condensation is another physical change so when steam turns back into liquid water that's condensation sublimation is another word you want to be familiar with think of dry ice dry ice goes directly from a gas I mean from a solid to a gas so if you take dry ice and you put it on a table it won't turn into a liquid it's going to skip the liquid phase you'll see gas coming off the dry ice immediately that's sublimation no wonder it's called dry ice it doesn't liquefy at least at normal pressure or atmospheric pressure If you increase the pressure you could make dry ice turn into a liquid but at 1 atm at C Level pressure it doesn't happen now there's another term you need to be familiar with a deposition deposition is basically the opposite of sublimation that's when a gas goes directly into a solid skipping the liquid phase so if you take carbon dioxide any Air at 1 atm standard pressure and if you cool it down you could freeze it back into dry ice so anytime you have a change in the state of matter it's a physical change so anytime a solid is converting into a liquid or liquid changes into a gas or vice versa all of those changes are physical in nature so keep that in mind now let's say if you have zinc metal reacting with acid so it's being corroded by acid that's another example of a chemical change any type of corrosion whether a metal reacts with oxygen in the air in the case of iron or if a metal reacts with acid and is corroded by it that's a chemical change anytime something reacts you have a chemical change now let's say if you take a piece of copper metal and you pull it into a wire is that a physical change or a chemical change taking a bar of copper metal and turn it into a very thin wire that is a physical change the wire is still composed of copper most metals are ductile and malleable the ductility of a metal has to do with ability to be drawn into fine thin wires which is good to make electrical circuits and if you could take a metal and Hammer into sheets that's the malleability of a metal it's malleable if it could be hammered into sheets so all of these are physical changes just the same way as if you take a piece of paper and you crumple it that's a physical change you still have paper now what about when silver tarnishes so when it loses its color and it develops that black tarnish is that a physical change or a chemical change when silver tarnishes the silver reacts with sulfur and it forms silver sulfide which is blackish in nature that's an example of a chemical change the chemical identity of the substance is changing and sometimes you can tell visibly based on the color change silver is turning black so that's a color change which indicates a chemical change so that's all I have for this video so now you know how to distinguish a physical change from a chemical change