Students must be able to calculate density from mass and volume measurements prior to doing this lab.
This lab exercise is actually 3 mini labs student teams work through. They will need access to scales that measure at an accuracy of .5 to .1grams as whole gram scales are not accurate enough to see the differences and make good comparisons. Students will also need rulers, calculators, and possibly beakers or graduated cylinders.
In the first mini lab students determine how mass will change as they add marbles to film canisters (I use the old black film canisters but they are rare to find now so you can also use old pill bottles without the labels or other small containers that are similar and are all the same volume). They will notice mass change as marbles are added bu the total volume of the canister not change as the empty canister had "air" which s being replaced by something with more mass per volume, thus greater density.
The second mini lab students will use two pre-made 10ml graduated cylinders one with water and the other with corn syrup. Both are colorless substances without very distinct smells it makes it harder for students to quickly know they are actually different substances. Prior to the lab add some corn syrup to one of the 10ml graduated cylinders (5-7ml or so). Then add enough water to the other 10ml graduated cylinders so that it has the same mass as the one containing the corn syrup. Label the corn syrup A and the water B with masking tape. Students find that two different volumes can have the same mass.
The third mini lab requires the use of small wood or plastic cubes that come with math base ten sets which are used to show single units. They work well because they are manufactured to be the pretty much the same size and mass. Students measure the mass and volume of one cube then determine it for 2 cubes, 3 and so on. They should notice a pattern after the 2nd cube that mass and volume increases at a constant rate of one cube of mass and volume. They can simply multiply the single cube measurements by the number of cubes being used. If not they should see it after they graph the data in this section. This shows students the density remains the same as you add more material of the same kind as materials containing the same compounds (we get to this again later using water) will have the same density as mass and volume increase at the same rate.