Amy Sass

LAYERS OF LIQUIDS

Concept: Density

The science concept in this experiment is density and polarity. Density is a measure of compactness, of how much tightly mass is squeezed into a given volume. It is the ratio of mass to volume. Polarity is the attraction between two substances.

Materials:

250 mL graduated cylinder

50 mL corn syrup (polar)

50 mL colored water (polar)

50 mL vegetable oil (non-polar)

50 mL alcohol (dyed w/food coloring) (polar)

Directions:
1. Pour the 50 mL of corn syrup into the graduated cylinder.

2. Pour 50 mL of vegetable oil into the cylinder.(Pour down the side, tilt the cylinder, preventing any mixture).

3. Slowly pour the 50 mL of colored warer on top of the vegetable oil and watch carefully what happens. Which solution is more dense, the water or the oil? The water is more dense as evidenced by the fact that the water appears to go underneath the oil.

4. Pour 50 mL of alcohol into the cylinder on top of the other liquids.

Introduction: Did you ever try putting liquids on top of one another? What happens? Usually all the liquids will mix together giving you an ugly yucky color. Let me show you a little trick. First I will add one liquid, this is kind of thick, like corn syrup. Next, I will add another brownish liquid, that smells like coffee. Third, I will add another semi-thick liquid, like vegetable oil. Finally, I will add another thin liquid.

Explanation: Some liquids can not be mixed, so they separate based on their destiny. Density = mass/volume. More dense liquids sink to the bottom, while the less dense liquids rise to the top. So each liquid is less dense. The one on the bottom is the most dense. Another factor which helps to keep the liquids from mixing is polarity. Polarity is the attraction between two or more substances. A polar substance has both positive and negative molecules. A non-polar substance has no charge. Alike properties mix, so two polar substances will mix, while not alike substances will not mix. Therefore, the way the liquids are layered (polar on top of non-polar), helps to prevent the liquids from mixing. Corn syrup on the bottom, colored water on top of the corn syrup, vegetable oil on top of the coffee, and alcohol on top of the vegetable oil. There is only one exception in the experiment: corn syrup and coffee are both polar. This is possible because the molecules in the corn syrup are very viscous, so it does not mix.

Safety Precautions:

Waste Disposal:

References:

Magic Science by Jim Wiese 1998