Return to Chemistry IndexDensity Determination

Marcea Anderson Thornton Township High School

150th & Broadway Ave.

Harvey, Il. 60426

708-596-1000Objectives:

(for jr. or sr. high school)

Purpose is to learn and practice techniques and calculations for determining

volume and density of a substance.Apparatus Needed:

Double pan balance, can of coke, can of diet coke, two evaporating dishes,

sugar. (demo.)

Density vial. (demo.)Recommended strategy:

Start by having a density vial sitting on the front desk for the students

to look at when entering the classroom. There are several kinds of denisty vials

that you can make for the classroom. A density vial uses several different

solutions and objects in one container, each having a different density they

will sink to their own level. Start with a plastic liter bottle or jar or a

large graduated cylinder. Pour in small amounts of the liquid solutions first

in the following order: syrup (1.36 g/cc), glycerine (1.26 g/cc), ethylene

glycol (1.11 g/cc), colored water (1.0 g/cc), oil (.9 g/cc),colored alcohol (.79

g/cc). Now, slide in the solid objects, they will sink to their level of

density within the solutions: lead piece (11.3 g/cc), rubber stopper (1.2

g/cc), plastic piece (.9 g/cc), oak (.9 g/cc), cork .2 (g/cc).

Give the students time to look carefully at the vial to notice the

different levels of the solutions and the objects placed in the vial. Ask the

students questions about the vial. "What do you see in the vial? Why is the

cork floating near the top and the copper piece is near the bottom?" Continue

asking questions until the students come to some conclusion that the solutions

and objects have different densities. You may change this lesson some what by

making the density vial as a demonstration. At this point, set the density vial

off to the side and tell the students that we will come back to this later in

the class period.

Bring out your double pan balance and soda cans. Ask the students about

the mass and volume of the two sodas. Then place the two cans on the balance,

the regular coke should be heavier. Ask the students why the regular coke is

heavier. Ask them what is in the coke that is not in the diet coke. (Hint:

nutrisweet is 200 times sweeter than sugar, so they only use a small amount of

it in diet coke.) Coke has a very sweet taste to it because of all of the sugar

added to it. Then ask the students ways to determine how much sugar is in coke

that is not in diet coke. Hopefully, the students will tell you to put sugar on

top of the diet coke can. You can do this by placing an evaporating dish on top

of each can, then add sugar to the dish on the diet coke can until the two cans

are balanced, this will give you equal mass of the two cans. Ask the students

questions about the soda cans. "What happened to the mass of each can? What

happened to the volume of the two cans? What do you suppose that this can of

each variable is telling us?"

At this point in the lesson, it will be necessary to explain the concept of

density. Talk about the variables in density and the formula for solving for

density. Go back to the denisty vial. Once again ask the students questions

about the vial, this time relating them towards the denisty of the various

solutions and objects. Your "recipe" for the density vial should list the

various densities of the solutions and objects to be used.