Density - a Physical Property  Physical Properties Elmhurst College
 Diet vs. Reg. Coke  Density of Ice  Density of Gold Chemistry Department
 Density of Liquids  Density of Gases   Virtual ChemBook

DENSITY Applications
with Liquids and Solids

 
DENSITY is a physical property of matter, as each element and compound has a unique density associated with it. Density defined in a qualitative manner as the measure of the relative "heaviness" of objects with a constant volume. For liquids the density may also vary with the temperature.

Density Comparison to Water:
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 vs. if a rock sinks, it is more dense than water.

 Liquid Density examples based upon differences in mass or weight per unit volume.

Density of a liquid with a constant volume, varies according to the weight. The higher the weight, the higher the density.

Layers of Liquids Demonstrations:
In this series of demonstrations the theme is that a variety of liquids have different physical properties as shown by their densities. The most dense liquids will be found on the bottom, the least dense liquid is on the top. See Table below.
Layers of Liquids - Demonstrations with Density

Any objects placed in the liquids will seek their own level depending upon the density. If an object has a density that is intermediate in value, the object will float between two layers.
Floating objects in water

Floating Spheres:
In the case of the floating spheres, the water is the most dense and hence on the bottom. If the alcohol is very carefully added to the water with only a minimal mixing, the alcohol will layer on the top of the water since it is less dense. The oil drops that are added are more dense than the alcohol so will fall through the alcohol, but will remain on top of the water. The oil is less dense than the water. See Table below.
Floating Spheres - Demonstrations with Density
Lava Lamp:
The lava lamp in this demo does not actually work on the principle of original electric lava lamp. In this case, a cylinder is prepared with water on the bottom and oil floating on the top. Small amounts of salt are added. Since salt has a high density of 2.16 g/mL, it forms a coat around some of the oil and causes it to sink, since it now has a higher density than water. As the salt covered oil drop rests on the bottom of the water, the salt dissolves into the water. When all of the salt has dissolved, the oil drop again rises to the top since it is now again less dense than the water. See Table below.
Lava Lamp - Demonstrations with Density

Other Demonstration Examples:
Nylon Rope:
The adipylchloride or (acid) solution is dissolved in hexane. The hexane is less dense than the the lower water solution and thus floats on top of the water. The chemical reaction occurs right between the two layers. See Table below.

Deep Purple Magic: In this demo, dichloromethane is added to water that contains iodine. The density of the dichloromethane is greater than that of the water, therefore it sinks to the bottom. During the demo, the iodine is extracted from the water into the dichloromethane and gives a very deep purple color.

 

 
 Density examples based upon differences in liquids and solids. The solid has a constant density, but the density of the liquids varies to give various effects.


Ice cubes in different liquids:
In this demo ice cubes are placed into two clear liquids which appear to be identical. One liquid is water and the ice cube floats. The other liquid is ethyl alcohol and the ice cube sinks. The ice cube has a constant density, but its behavior changes because of the different densities of the liquids. See Table below.

Mysterious Ice - Demonstrations with Density


Eggs in different liquids:

Again in this demo, the egg has a constant density, but the liquids have different densities. If the egg is more dense than the liquid it will sink as in plain water. If the liquids is more dense than the egg, it will float as in the case of the salt water. See Table below.
Egg Densities - sugar water/oil
Floating Eggs - sugar and water - Demonstrations with Density

In one case, the egg floats in hydrochloric acid because the bubbles of carbon dioxide attach to the side of the egg and make it less dense than the water so that it floats.
Smart Eggs - salt water and acid - Demonstrations with Density


Liquid Density examples based upon differences in temperature.

There are a number of changes to the structure of water or any other liquid that occurs with increasing temperature. The water molecules gain energy which is used to bend and break the hydrogen bonds. On raising the temperature, the size of ordered clusters of water molecules decreases, the number of smaller clusters increases, the number of hydrogen bonds decreases and the average distance between the water molecules increases.


Underwater Volcano Demonstration: What makes hot water rise? As stated above, the hot water has less hydrogen bonds and the spaces between water molecules increases. The net effect is to have less mass per unit volume. This translates into a lower density. The lower density water floats on top of the denser cold water. In the photo, the hot water is colored with red dye to make it more visible.

 Demonstrations with Density
Mysterious Ice
Layers of Liquids
Egg Densities - sugar water/oil
Smart Eggs - salt water and acid
Floating Eggs - sugar and water
Floating Spheres
Lava Lamp
Underwater Smoke Stack
Floating objects in water
 

 

 Densities of Common Compounds

 Substance

 Density
grams per mL

Hexane 

0.660

Ethyl Alcohol 

0.789

 Rubbing Alcohol

 0.79

 Ice 

0.92 

Corn oil

 0.93

 Water 

1.00

 Sea Water (3%)

 1.03

25% Salt water

1.25

Dichloromethane

1.3 

 Corn Syrup

 1.38

 Salt

 2.16