A Denser Coke
Grade Level: 5th - 8th; Type: Chemistry/Food Science
The goal of this experiment is to learn about density by comparing the relative density of cans of Coke to Diet Coke.
- What is density?
- Ice cubes float in water. Does the density of water depend upon the physical state of the water? Why?
- Salad dressing generally separates into two layers of oil and vinegar. What does this say about the relative density? Do you think it would separate into layers even if there was the same volume of oil and vinegar?
- How is density related to buoyancy?
- When you throw a rock into water, the rock sinks. A cruise ship is far heavier than a rock yet it doesn’t sink. Why?
The concept of density seems to stump many students. It is easy to understand weight and volume because weighing goods and measuring amounts are things we do every day. Density is somewhat more elusive because it involves both weight and volume. Density can be defined as mass per unit volume. If two items have the same size (that is, the same volume), but different weights, their density is different.
- Can of Coke
- Can of Diet Coke
- Two 500 ml or 1 liter beakers
- Triple beam scale
- Fill both beakers ¾ full of water.
- Place the can of Diet Coke in one beaker and the can of Regular Coke in another. What happens? If you have a camera, take a picture of the two beakers with the cans of soda in them.
- Take the cans out of water and weigh them. Write down how many kg the cans weigh. Using kg may seem somewhat odd, but this will be important in step #5.
- Check the label to determine the volume of the cans. Make sure you know volume in milliliters. Don’t worry about the contribution of the aluminum can to the total volume.
- Plug the values you obtained in steps 3 and 4 to the formula for density.
D stands for density, M stands for mass and V stands for volume
Calculate the density of both cans. The SI units for density are kg/m3. Since 1 ml equals 1 cm3, one g/cm3 = 1000 kg/m3. Double check your conversion and make sure your decimal points are in the right place. Do the values you obtained explain what you observed in step 2?
Terms/Concepts: Mass; Volume; Density; Buoyancy; SI units
- Gonick, Larry and Craig Criddle. The Cartoon Guide to Chemistry. Collins Reference (2005).
- What is Density? (http://www.elmhurst.edu/~chm/vchembook/120Adensity.html)
- Density (http://en.wikipedia.org/wiki/Density)
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