hello my name is Adam and today we're going to go over some practice problems using the density equation the density equation is density equals mass over volume so we can use this equation when we have an unknown metal and we want to determine what it is so say we have an object that we think is gold but we're not sure so we look up the density of gold and then we also think it could be fulls gold which is pyite so look up that density too the density of gold is 19.3 G per milliliter and the density of pyite is 4.8 G per Mill so now we determine what the density of our object is by calculating the mass and the volume and then we can deter see which one of these it's closest to so we'll determine the mass by putting on a scale and weighing it and we find that the mass mass is equal to 1,119 G and we'll determine the volume by placing our unknown object into a beaker of water the initial volume of this Beaker is 100 ml after we add our unknown object the final volume is 158 Mill so that tells us that the difference between these two has to be the volume of our object so the volume of our object is 58 ml so now we have the volume and the density which we can plug into our density equation and then compare that back to our known values so divide 1,1 19 G ided by 58 millit that gives us a density that rounds to 19 G per Mill so we determined that it rounds to 19 19 G per Mill and that's closest to our gold density so we conclude that our object is in fact gold next we're going to use our density equation in a different way so now we're going to use our density equation to solve for the mass of something we might want to do this because the scale on our WS broken or for another re don't have a scale but we know the identity of our object and we can calculate the volume so in this case we have aluminum and we know the density of aluminum is equal to 2.7 G per Mill and we can calculate the volume like how we did in the last problem we're going to put it into a container of water and measure the volume change so the initial volume once again is 100 m we add our object and the final volume is 110 M um so then the difference between these two is 10 m that's the volume of our aluminum block we can then use these two variables to solve for our maass but first we have to rearrange the equation we'll do this by multiplying both sides by V when we do this these two cancel out so we get mass by itself so we have volume * density equals mass and we just determined that the volume is 10 m and the density we looked up is 2.7 [Music] G per milliliter so that tells us that the mass of our object is 27 G all right so this is how we can use this equation to solve for a mass when we don't have the mass and don't have any other way to figure it out next we're going to use this equation to solve for the volume when we can figure out the mass and know the density once again we need to rearrange our equation that we started with which is mass over volume we'll start by multiplying both sides by volume this gives us volume time density equals mass and then to get volume by itself we divide both sides by volume or sorry excuse me by density this cancels out density on this side and gives us volume equals mass over over density so now we're going to determine the volume and our object that we have is iron so we know the density of iron is 7.8 G per Mill and we put this object this iron object onto a scale and determine that the mass is equal to 92 G so we can plug these two things into our density equ which is now solving for volume and determine the volume so 92 G / 7.8 G per Mill tells us that our final volume is 12 M all right so this shows us how we can use the density equation to solve for volume and in the last problem we saw we can solve for mass in the first problem we saw we can solve for density using this equation so I hope you've learned more about how to use this equation and I hope you have a good day thank you