The objective of this project is to use paper chromatography to analyze ink
components in permanent black markers.
Matter makes up everything in the universe. Our body, the stars, computers,
and coffee mugs are all made of matter. There are three different types of
matter: solid, liquid, and gas. A solid is something that is normally hard (your
bones, the floor under your feet, etc.), but it can also be powdery, like sugar
or flour. Solids are substances that are rigid and have definite shapes. Liquids
flow and assume the shape of their container; they are also difficult to
compress (a powder can take the same shape as its container, but it is a
collection of solids that are very small). Examples of liquids are milk, orange
juice, water, and vegetable oil. Gases are around you all the time, but you may
not be able to see them. The air we breathe is made up of a mixture of gases.
The steam from boiling water is water's gaseous form. Gases can occupy all the
parts of a container (they expand to fill their containers), and they are easily
Matter is often a mixture of different substances. A heterogeneous mixture is
when the mixture is made up of parts that are dissimilar (sand is a
heterogeneous mixture). Homogeneous mixtures (also called solutions) are uniform
in structure (milk is a homogeneous mixture). A sugar cube floating in water is
a heterogeneous mixture, whereas sugar dissolved in water is a homogeneous
mixture. You will determine whether the ink contained in a marker is a
heterogeneous or homogeneous mixture, or just one compound.
In a mixture, the substance dissolved in another substance is called the
solute. The substance doing the dissolving is called the solvent. If you
dissolve sugar in water, the sugar is the solute and the water is the solvent.
For this project, you will be making a small spot with an ink marker onto a
strip of paper. The bottom of this strip will then be placed in a dish of water,
and the water will soak up into the paper.
The water (solvent) is the mobile phase of the chromatography system, whereas
the paper is the stationary phase. These two phases are the basic principles of
chromatography. Chromatography works by something called capillary action. The
attraction of the water to the paper (adhesion force) is larger than the
attraction of the water to itself (cohesion force), hence the water moves up the
paper. The ink will also be attracted to the paper, to itself, and to the water
differently, and thus a different component will move a different distance
depending upon the strength of attraction to each of these objects. As an
analogy, let's pretend you are at a family reunion. You enjoy giving people hugs
and talking with your relatives, but your cousin does not. As you make your way
to the door to leave, you give a hug to every one of your relatives, and your
cousin just says "bye." So, your cousin will make it to the door more
quickly than you will. You are more attracted to your relatives, just as
some chemical samples may be more attracted to the paper than the solvent, and
thus will not move up the solid phase as quickly. Your cousin is more attracted
to the idea of leaving, which is like the solvent (the mobile phase).
Chromatography is used in many different industries and labs. The police and
other investigators use chromatography to identify clues at a crime scene like
blood, ink, or drugs. More accurate chromatography in combination with expensive
equipment is used to make sure a food company's processes are working correctly
and they are creating the right product. This type of chromatography works the
same way as regular chromatography, but a scanner system in conjunction with a
computer can be used to identify the different chemicals and their amounts.
Chemists use chromatography in labs to track the progress of a reaction. By
looking at the sample spots on the chromatography plate, they can easily find
out when the products start to form and when the reactants have been used up
(i.e., when the reaction is complete). Chemists and biologists also use
chromatography to identify the compounds present in a sample, such as plants.
Terms, Concepts and Questions to Start
- adhesion, cohesion forces
- capillary action
- stationary phase, mobile phase
- hydrophilic, hydrophobic
- Rf value
- paper chromatography
- Why do different compounds travel different distances on the piece of
- How is an Rf value useful?
- What is chromatography used for?