Sometimes we want to measure something that is difficult to do directly. It is often possible to use an indirect method whereby we do easier measurements and then calculate what must be the desired measurement. (Some view such an ability to find the easiest method to reach an answer is a sign of intelligence.) This experiment will use an indirect method called displacement
Consider some sand: The grains must not fit tightly but rather have gaps between the grains, probably usually filled with air. How much space is between the sand grains? For industries who need to pack material into the minimum of volume, this might be considered wasted space. For creatures that live in soil, this is vital space that provides room for essential water and oxygen. For plants, soil that packs too tightly with little volume for water could doom survival in dry times. For a company that produces concrete, knowing the amount of space between gravel allows the maximization of profits by minimizing sand and cement.
For a selected sample of sand, gravel, or other granular material, determine the percentage of volume between the granules. Recall from Experiment 1-3 that there can be difficulties transferring materials from one location to another. Minimize losses due to transfers.
Divide the volume of air by the granular volume (step 1), then multiple by 100% to determine the percentage of volume between the granules.
Record your results in your science journal and write a formal report to earn credit.
Measure and compare the space in other granular materials. Does it make a difference if the granules are nearly the same size, or of diverse sizes? Does it make a difference if the granules have sharp edges or rounded edges. Does it make a significant difference if the granules are uniformly large or uniformly small?
In future experiments we will use volume as a fast measure of materials whenever we can. If you are not working in a well stocked laboratory, it would be helpful to begin to collect a variety of volume measuring containers. Calibrate each by comparing to your standard graduated cylinder. For example, fill a table spoon with water then transfer to the cylinder to measure. Keep a record in your science journal of the volume of each container in your volume set.