hi kids miss block here and thanks for joining me today as we discuss density ready let's get started so what exactly is density density is the amount of matter in a given space so if we were to look at this diagram right here all the way on the left you can see that we have a few atoms in this box and they're fairly spread out they're not crowded it doesn't have a very high density instead it has a very low density as we move to the right you can see that there's more and more atoms and it's getting more and more crowded right here we have a lot of atoms in this space it has very high density we have more matter in that given space as compared to this on the Left we can see this often when we look at a density column so in this picture right here I know pretty colors right we have this red liquid floating on top of all the other colors the reason it's floating on top is because it has the least amount of matter in a given space that's the lowest density likewise that purple liquid on the bottom has the most amount of matter in a given space it is the most dense so if we recall our picture from before the atoms are spread out in this red liquid compared to the atoms in this purple liquid they're going to be more compact this kind of applies to this problem we going to look at next this might look a little familiar so try to answer it now pause the video I'm going to keep going so in this example right here we're asking what would happen to a piece of quartz as we drop it through a density column and we're going to ask where this quartz that has a density of 2.7 grams per cubic centimeter is going to do what's going to end up with it the answer this problem is actually going to be d it's going to pass through W X&Y but not Z the reason is is because the density of the course is 2.7 grams per cubic centimeter while W has a density of one gram per cubic centimeter x has a density of 1 point 8 gram for a cubic centimeter and Y has a density of 2.3 grams per cubic centimeter so the atoms in W X why they're spread out more they're much less dense they're going to float or allow the courts to pass through however Z has a much greater density those atoms are much more crowded together okay there's much more matter in a given space for Z so courts will actually end up floating on layer Z it will not pass through density has many applications in earth science or we look at it and influences a lot of different earth processes for example if we're gonna look at the layers of the earth and you think back to that density column we looked at the earth itself is like a giant density column the denser materials are towards the center of the earth and the less dense and least dense materials are closer to the surface we're going to add the water and the atmosphere on top of that to you would even have a greater density column all right because the atmosphere is resting on top of the hydrosphere now density can be expressed mathematically through the following formula density equals mass over volume and that's why before that definition might have sounded familiar because we kind of combine these two factors together mass remember is the amount of matter in a given space and we express mass and grams and volume is the amount of space an object takes up and we can express that either using cubic centimeters or milliliters let's look at another sample problem well before the sample problem remember you could find density on the front page of your reference tables that equation so what you need to know is right there you do not need to memorize this formula now let's try a simple problem so shown to the right we have an empty 1000 milliliter container has a mass of 250 grams when filled with the liquid the container and the liquid have a combined mass of 1300 grams what's the density this liquid take a moment to solve it out pause it I'm gonna keep going this is the solution to it so the answer is actually going to be be taking my equation for density so it's going to be density equals mass over volume now I have to find the mass of the liquid I know that the beaker sorry the graduated cylinder has a mass of 250 and then the graduated cylinder and liquid have a mass of 1300 so if I take 1300 and subtract the mass of the graduated cylinder I'll get the mass of just the liquid and that works out to being 1050 grams I also know since I filled the graduated cylinder I'm going to have a volume of 1,000 milliliters so I take 1050 grams divided by a thousand milliliters and I end up getting an answer of 1.05 grams per milliliter and my answer ends up being B sometimes you're asked to manipulate a density formula so they'll give you density and you need to find um mass or maybe you need to find volume they'll give you two of those variables so you can use something called a density triangle if you have trouble manipulating equations now the key is is that you have to memorize where all the variables go in the triangle because if you don't you're gonna mess up as always I do recommend doing the math out but I know some of you do struggle with maths so for example if I was looking for the mass I would cover up that mass and now I'm left with density and volume since in the triangle they're next to each other we're gonna multiply them so we end up getting mass equals density times volume likewise I was looking for volume I cover up the V and I see that mass is over density so as a result volume equals mass divided by density now if I change the shape or size of an object as its density change let's take a look at these two items right here aluminum foil we should all be very familiar with that right so on the Left I have a roll of aluminum foil and on the right I have bars of aluminum now which one's more dense you might be inclined to say the bars of aluminum but since they're made of the same substance there's no change in density they will have the same ratio of mass to volume so they have the same amount of matter in a given space let's take a look at this graph this is not aluminum but instead this is pyrite all right and I have taken five samples of different sizes of pyrite and they've been plotted on this graph so let's say we looked at a smaller sample of pyrite right have mass of 50 grams in a volume of 10 cubic centimeters I solve out its density and I find this five grams per cubic centimeter now I'll take a bigger piece of pyrite one that has a mass of 150 grams and a volume of 30 cubic centimeters I solved that one out and I find that its density is five grams per cubic centimeter so while the size might have changed and while one might have felt lighter because it was just smaller the ratio of best of all I'ma stay this aim I will still find the same amount of matter in a given space in each sample there's density is the same there is no change in density let's take a look at this sample problem pause it solve it out but I'm going to keep going so we're looking back at our old friend aluminum here and a student calculate a density of five different pieces of aluminum base you know each having a different volume which graph best represents the relationship so they had a different volume they were each at different size however they're all still aluminum they haven't had any changes to them so as a result the density should not change so we want to find a constant relationship and that would be a as a volume increased the density stayed the same now there is a way to change the density and this change is density of an object we need to find a way where we can change the volume without changing the mass because if we can change the volume we can cause the matter to become more compact squish those atoms together more or we can go and we can make you know make those add spread out increase that volume and this can either be done by a change in pressure or a change in temperature pressure alright as I increase the pressure on an object the volume will decrease an inverse relationship since the volume is decreasing without a change in mass the density will increase thereby causing a direct relationship you can see that right there this happens with metamorphic rocks they increase pressure on them and the atoms get more and more compact as a result they will be much more dense temperature works in the opposite way as temperature increases the volume in it will increase since the volume is increasing those atoms can really spread out and as a result the volume is increasing without a change in mass that density will decrease giving us an inverse relationship that's why if you think about it when you have like a hot air balloon you're heating up that air and the molecules are spreading out and they're getting warmer and warmer and the hot air can rise up however water is kind of a unique substance because if you think about what we just said substances should be most dense in the solid phase but that's not the case is illustrated by our picture here because the ice is floating alright so with most things should be most dense in the solid phase ice is floating in water thereby signaling that it must be less dense well think about this with water when it freezes when water drops below 4 degrees Celsius that's when water's most dense 4 degrees Celsius ok our three point nine eight according to the reference tables um you know it will start to freeze and if anybody's put a can of soda in the freezer what happens to that can it explodes why is it explode because the water in the soda starts to expand all right increasing the volume instead of having the volume contractor shrink all right so as water freezes it expands the volume is increasing thereby making it less dense than liquid water hopefully this video is able to help you and you got a lot from it and understanding density feel free to watch it again or come to extra help I'll see you again soon take care bye bye I have a special guest who made it all possible because they took a little nap say hi nope nope okay this is what happens when they just wake up I love you boy