in this video we're going to look at the concept and equation behind density and finish off by looking at how we're going to find the density of unknown solids and liquids experimentally density is just a measure of how much mass a substance has per unit of its volume so to find it all we need to do is divide these substances mass by its volume or to put it into a formula triangle would look like this because the symbol for density is the greek letter rho which looks like a p and because mass is measured in kilos and volume is measured in meters cubed in physics density is normally measured in kilos per meter cubed so if we take a solid aluminium as an example which has a density of 2 2710 kilos per meter cubed that means that a single one meter cube block of aluminium would have a mass of 2710 kilos we can also measure density in other units though with the common one being grams per centimeter cubed and if you want to convert the two just remember that one gram per centimeter cubed is equivalent to 1 000 kilos per meter cubed so aluminium has a density of 2.71 grams per centimeter cubed as an example question let's calculate the volume of 420 kilos of aluminium in the exam that tell you that the density is 2710 kilos per meter cubed you'll just have to rearrange the equation to work out the answer if we use the triangle we can see that to calculate volume we have to divide the mass by the density so we just do 420 kilos divided by 2710 which gives us a volume of 0.155 meters cubed the next thing we need to look at is how to calculate the density of a solid or a liquid experimentally let's start with solids if we think back to our equation we can see that in order to find the density we're first going to have to find the mass and the volume of our object finding the mass is the easy part we just place our solid on a balance and measure the mass the volume though is a bit trickier and depends on whether it's a regular or irregular shape if it's regular like some kind of cube or cuboid then we can find its volume by measuring and then multiplying its length width and height so for this cuboid here its volume would be four times three times two so 24 centimeters cubed however if the solid is irregular then we have to find this volume using a eureka can that's been filled with water and an md measuring cylinder the cool thing about eureka cans is that they have these outlets on the side which allows water to flow out and be collected by the measuring cylinder this means that as long as it's filled right up to the outlet when we add our solid substance to the eureka can a volume of water exactly equal to that of the solid would flow out of the can and into the measuring cylinder allowing us to measure the exact volume of the solid whichever of these two techniques we used though we now have both the mass and the volume so to find the density all we need to do is plug the values into the equation now to find the density of a liquid is a bit easier all we have to do is place an empty measuring cylinder onto a balance and zero the balance to resetter then we pour some of the liquid into the cylinder for example 10 milliliters which is the same thing as 10 centimeters cubed and we record the mass of that amount of liquid then we just divide the mass by the volume and that gives us our density in general the larger the volume that you measure the more accurate your density will be because it minimizes the effects of the uncertainty in taking your measurements you can also take multiple measurements so that you can identify any anomalies and also calculate a mean anyway that's everything for today so hope you found it useful and we'll see you soon