 The water replacement method is a method that allows us to measure the volume of an object that is oddly shaped, for example a spoon like this. Why would I need to know the volume? I need to know the volume if I want to calculate the density of an object. The mass of the object can easily be obtained by putting on a scale, but the volume, if it's oddly shaped, cannot. According to legend, the method was invented by Archimedes when he was tasked to figure out if a crown was really made out of gold. He could figure out the mass, the density of the crown, but the problem is he couldn't figure out the volume. It was oddly shaped and melting the crown down to measure the volume was not really an option. So he was blocked and he didn't know what to do until one evening when he was going to take a bath, when he realized that when he steps inside the bath, the water level inside the bathtub raises by some amount which is exactly equal to the amount of volume that his body was submerged. So apparently, the moment he figured that one out, he was getting out of the bathtub, running down the street and screaming Heureka, which apparently means I have found this in Greek. Now let's use this method to figure out the density of my spoon. I'm not going to use one spoon, I'm going to use several spoons. Why? Because if you use more mass, then we have also more volume, that means you will have probably a higher precision and our result is going to be better. So if you can, use several objects at once. So first of all, I will need a container in which I can completely submerge my spoons because if they cannot be completely submerged, the experiment will not work. If they're not completely underwater, you will not get the correct volume. So I used my cup here and I marked where the cup is empty and where is one liter of water in my cup. I knew this in this case because there was a real line here that told me where the liter is. When I measured the distance between those two lines, I got that 14.5 centimeters, corresponded this around my liter, I'm sure about the one. I'm not so sure about the second digit, so I write it with two significant figures. So here is my liter. So now all I have to do is to submerge my spoons for which I can quickly measure my mass by putting them on a scale. So I get 114 grams, 114 grams. Again, I'm using several spoons instead of one because the density is a material property. It doesn't matter the amount of material you take. If I take more mass, I will get more volume. With higher amount of material, I will get a better precision. So I dumped my spoons in the water and I'm going to measure by how much my water volume raised from the line I had previously drawn. It's a bit difficult because I don't have so many spoons in there. What I get is a difference of about 0.3 centimeters. Now how do I convert the centimeters into volume? Well, I have my own unique conversion here. I want to get rid of the centimeters. I put my 14.5 centimeters at the bottom and my liters at the top. So I get 0.3 divided by 14.5. It gives me 0.02 liters or around 20 milliliters. Note I'm going to write down the final answer with only one significant figure. I'm going to keep however for the calculations that I had actually 20.6 here. I look at my calculator. So I'm rounding at the very end and I'm going to put here in the 20 milliliters in the calculator. I'm using 20.6. And what I get is 5.5. However, I only had one significant figure. So I'm going to report this as 6 grams per milliliter. You see that my answer only has one significant figure. That means actually also the 6 could have been a 5, could have been a 7. But at least it gives me an order of magnitude. And of course if I want to get more precision I need a better measuring device. Or alternatively I could use more spoons. The main problem here was that I only got a very little water displacement. So if I had used many more spoons, hopefully I would have gotten a bigger value here which then would have increased my precision.