hi I'm Jason welcome to the section of the chemistry tutor here we're going to learn about the very important topic of density density is important because it's a physical property of everything around us and so when we start to learn about different elements and compounds and their properties density of the material is just going to be something that pops up over and over again so let's spend some time here talking about what that means so that when you see the word density in your book you're not worried about it you're not taking aback by it you totally understand what that means first of all density is a word that we use in our everyday language so most of you most of us have some idea what density might mean even without talking about chemistry so ask yourself that what do you think the word density means usually we talk about something being dense or not being dense and usually when something is dense it means it's hard to understand somebody's dense maybe they're hard to get along with something like that that's sort of what we mean in our everyday language but getting more towards the the language of science if you think about what's something that's dense might mean you might think of something being heavy you might think of something having mass because it's very dense material you might think of lead being very dense because it's this big heavy thing you might think of feathers not being so dense because this kind of this lightweight stuff so you know that mass / weight play a part in the definition of density but that's only part of what we're going to define that we have so the first thing you need to sort of know and I know that you all know this is that everything around you has mass right this marker has mass I can put it on a balance and I can figure out what its mass is I can tell you that this has maybe like six grams of mass here right but this marker also has a volume associated with it I can calculate that it's basically a cylinder so I know the radius of the cylinder I know how long the cylinder is I know some math so I can calculate the volume of this guy so I know its mass because I can measure that and I know its volume because I can measure that - and what happens is if you take the mass and divided by the volume you get what we call density its mass per volume or mass divided by volume however you want to think about it basically in layman's terms density is trying to tell you how much mass something has compared to how big it is because when you think about it for a second the mass of an object you know I'm the mass of a pile of lead here yeah it's important to know what that is maybe but the mass of a pile of lead is not really a great property of the substance because maybe my pile is this big maybe my pile of lead is this big maybe my pile of live is as big as a house so when I measure the mass of something that's useful to know but it's not the whole story if I'm talking about the property of the thing because I may have a truckload of of lead likewise maybe I have three feathers in my hand that I can take the mass of those feathers not going to be too much weight or too much mass but what if I have you know an entire backyard full of feathers or maybe an entire basketball stadium full of feathers it's gonna make me have a lot of mass but it takes up so much volume so when you really want to compare two things you can't just talk about the mass usually you need to talk about the mass in relation to how much space it takes up which is the volume so that's why we define something called mass per volume and that's what we call density so let's go and put some numbers to it make sure you understand so we're talking about the topic of density all right so what we know is that objects object has a mass in kilograms you can measure it in grams you can measure it in kilograms you can measure it in other units but they're all