Density is the amount of matter that is inside a three dimensional object. The more dense an object is, the faster it will fall or sink, even the smallest change in density can cause two bodies of water to be separated. For example salt water is slightly more dense than freshwater so you can have a layer of freshwater that is floating on top of the salt water. If an object is less dense than water it will float, like most wood. But if it is more dense it will sink, like steel or rocks. The formula for density is mass (or weight) over volume. Mass/weight is the measure of gravity that is pushing down on an object, and volume is the amount of space inside of an object. So in order to find the density of an object you divide the mass of an object by the volume of the object. That is the direct way of finding density, using the formulas. There is also an indirect way of finding the density of an object, which is the amount of water that it displaces. That amount is the density of the object.
Part one
In this part we weighed and measured all of our marbles of every material, we used wood, metal, and glass marbles. We used those measurements to calculate the volume of each sphere, we already had the mass. We then used both of those measurements to find the density in pounds over inches cubed. Then had to convert them to grams over centimeters cubed. In order to solve for the density of each sphere we had to divide the average mass by the average volume to get the density. Then I created a conversion table to convert pounds over inches cubed to grams over centimeters cubed. All three of the densities that we calculated corresponded to the published values.
Part two
In part two we used wooden cubes to determine the relationship between mass and volume. We weighed the cubes at different intervals, the intervals were 1, 2, 3, 4, 7, and 10 cubes. And we measured the dimensions of one cube and used those to calculate the volume of each intervals of cubes. As the volume increased, the mass increased, or you could say that as the mass increased the volume increased. Then we converted the volume from inches cubed into centimeters cubed.
The meaning of the slope of this graph is how much the volume and mass increases with each cube you add. Even though you don't go up by one cube each point on the graph, if you draw a line through the points that represents the slope you can use that to figure out the volume and mass for each amount of cubes. The graph is linear because the cubes are all the same and that causes the two values to increase by the same amount each time.
Part three
In this part of the project we used water displacement to find the density of the plastic materials that are used in automoblox vehicles. In order to find the volume of each object we used the water displacement, and weighed them to find the mass. Then we used the density formula (mass over volume) to solve for the density. It is possible that either ABS or Polystyrene, the densities of both are very similar.
Conclusion
I learned a few things during this lab. One thing I learned was that the measurements had to be fairly precise in order to get the density in a reasonable range, and that it is a pretty tough thing to do, and is time consuming, despite how easy it seems. Some limitations of the calculated volume measurements is that sometimes the shapes are too weird to get proper measurements of them. And with the water displacement sometimes with certain materials it could tamper with the mass measurements, like when wood soaks up water. But it could also be harder to get a really precise measurement. In my opinion the most accurate way to determine density is to solve for the volume of an object, and divide the mass by it, it leaves less room for error. If you know the density of an object you can look up what materials have that density and make an educated guess based on that. Mass exists everywhere, but weight only exists on earth because it is the force of gravity on an object.