Experiment 1.4

Christie W. 09/09/08

Experiment 1.4

The Density of Liquids

A. Purpose:

The objective of this experiment is, by performing this experiment, to view the way that liquids will arrange themselves in a glass due to their differing densities.

“Density is a physical property of matter, as each element and compound has a unique density associated with it. Density is defined in a qualitative manner as the measure of the relative "heaviness" of objects with a constant volume. For example, a rock is obviously denser than a crumpled piece of paper of the same size; a Styrofoam cup is less dense than a ceramic cup. Density may also refer to how closely "packed" or "crowded" the material appears to be - again refer to the Styrofoam vs. ceramic cup. In chemistry, the density of many substances is compared to the density of water. Does an object float on water or sink in the water? If an object such as a piece of wood floats on water, it is less dense than water. Conversely, if an object such as a rock sinks, it is denser than water (Virtual Chembook).”

Water has a density of 1 g/cm³ at a temperature of around 4ºC. Oil’s density varies at temperature (as is the case with most substances), but stays under the max density of water, meaning that oil will float on water. Likewise, syrup has a higher density than water (about 1.3), which means that syrup will sink in water.

This experiment hopes to show that, since many liquids have differing densities, they will layer themselves according to density when placed together, with the denser liquids on the bottom and the less dense liquids on the top.

Density influences many natural processes in nature, and therefore scientists need to understand this concept to better interpret things such as currents and overturn in the ocean.

Hypothesis: If the oil, water, and syrup are placed in the glass, then, because of their differing densities, they will form into distinctive layers within the glass; the oil will form the top layer, then the water in the middle, and then the syrup will sink to the bottom.

B. Equipment:

1. Water

2. Vegetable oil

3. Something that measures the volume of a liquid, preferably in mL or cm³. A graduated cylinder would be ideal, but measuring cups will work as well.

4. Maple syrup (natural syrup does not work as well as something like Mrs. Butterworth’s®.)

5. A large glass

6. A mass scale, preferably one that reads in grams. (The scale should not go much over 500 grams, or it will be very difficult to read the mass of the objects in the experiment.)

7. Safety goggles

C. Procedure:

1. First, measure the mass of the graduated cylinder, or whatever is being used to measure the volume of the liquid. Be sure to write it down with the correct precision. If a standard mass scale from a grocery store is being used, its scale is probably marked off in units of 10 grams. Thus, the mass measurements should be in a precision of 1 gram.

2. Next, measure out 50.0 mL (1/4 sup if measuring cups are being used) of syrup. Now put the graduated cylinder from this number (using the rules for significant figures) to get the mass of the table syrup by itself. This method of measuring mass if called the difference method. Chemists often call it “measuring the mass by difference.”

3. Now that the mass of the table syrup has been measured, and the volume of 50.0 mL has been verified (as this was the volume measured out), divide the mass by the volume to get the density. Be sure to follow the significant figure rules while doing this. Finally, pout the syrup into the tall glass. Repeat this procedure for both the water and the vegetable oil.

4. Once the density of all three substances has been measured, look at the tall glass. The table syrup should be all at the bottom of the glass, the water should form a layer above that, and the vegetable oil should all be in one layer at the top.

5. Clean up the mess.

D. Observations:

1. The graduated cylinder has a mass of 26g.

2. The experimenter is skeptical of whether or not ¼ cup will fill the graduated cylinder to the 50.0 mL mark.

3. The graduated cylinder does indeed hold 50mL, and thus the volume of the syrup placed in the cylinder is 50.0 mL.

4. When measured, the syrup has a mass of 55g.

5. Using the density formula, the experiment decides that the density of the syrup is approximately 1.1 g/mL.

6. The experimenter decides to do the oil next to maximize the interest when the water is poured in.

7. The mass of the oil is 43g.

8. Once again, using the density formula, the density of the oil is 0.86 g/mL.

9. As the experimenter pours the oil into the glass of syrup, the syrup repels the oil and thus the oil forms a layer on top.

10. The mass of the water is 50g.

11. The density of the water is 1.0 g/mL

12. When the experimenter pours the water into the glass, the liquids form distinct strata.

13. Just for fun, the experimenter puts an ice cube in the glass to see where it will go.

14. The ice cube stays half in the layer of oil and half in the layer of water.

E. Conclusions:

Through experimentation, the above hypothesis was supported, in that when the experimenter poured the liquids into the glass, they separated into distinct layers within the glass because of their differing densities.

In this experiment, the experimenter took a graduated cylinder, measured its mass, and then put syrup into the glass. Using a mass scale, the experimenter measured the mass of the syrup: 55g. Then, using the density formula (mass/volume), the density came out as 1.1 g/mL, meaning that the density of the syrup outweighed that of water, which is 1 g/mL. The difference in density caused the syrup to sink to the bottom of the glass and the water to layer on top of it. When the experimenter measured the density of the oil, it came out as .86 g/mL, meaning that it would float on water due to its relatively low density. This idea held true. In the end, then, the syrup sunk to the bottom, the water formed a layer in the middle, and the oil stayed in a layer on top.

This experiment could have been improved by using a thinner glass; this would allow for a larger distinction between the layers, therefore increasing the effectiveness of the layering and of the experiment.

Ideas for further research were generated by the way the ice cube floated in between the water and the oil; the experimenter thought that the ice cube would float on top of the oil. The experimenter wonders if it was because the experimenter let the ice melt for a time.

F. Bibliography:

Domain: http://www.elmhurst.edu

Document: /~chm/vchembook/120Adensity.html

Rosenoff, Steven. Class Lecture. 09/07/08

Wikipedia contributors, "Density," Wikipedia, The Free Encyclopedia. 10/17/08.

Domain: http://en.wikipedia.org

Document: /w/index.php?title=Density&oldid=244719343

Wile, Dr. Jay L. Exploring Creation with Chemistry, 2nd Edition. Apologia Educational Ministries, Inc. 2007