3M Science at Home: chromatography capillary action experiment


How does capillary action make chromatography possible?

Key Concepts

  • Capillary action icon
    Capillary action
  • Chromatography icon
  • Adhesion icon


  • Density icon

  • Introduction

    Imagine for a moment a tree in your yard or a local park. How does that tree get the nutrients it needs to live and grow? It is true that it obtains energy from sunlight, but it also acquires water through its root system. Does this occur due to absorption, or is there a more specific way to describe what is happening? How does the water go up into the tree, moving against gravity? Why doesn’t the water more or less drain back down and out of the tree? Trees use capillary action to move fluids around their systems. With this activity you will explore how capillary action makes chromatography possible, why it is such an important scientific process, and a few of the ways it can be utilized by chemists and engineers for scientific exploration.

  • Background

    You’re probably familiar with capillaries as they pertain to your body, but by definition they are any tube that has an internal diameter of hair-like thinness. Capillaries are a fundamental structure for life on earth as things like circulation and growth depend on that method of movement. Capillary action is when liquids can flow in a narrow space, even against gravity. If you have ever dipped a paintbrush in paint or water, the paint fills the paintbrush because of capillary action. Since gravity is so crucial for our planet to function, there must be a way for things to run counter to that force so that life can still thrive.

    In our experiment today, you’ll learn that chromatography is the separation of a mixture (our marker ink) by passing it in a solution (water) through a medium (coffee filter) in which the components of the mixture (the various colors that make up any given marker color) move at different rates. Capillary action is important to the process of chromatography because it allows a liquid to move through a medium. The first controlled chromatography tests were very similar to the experiment we will do today- dye makers used chromatography to test the mixtures of dye they were using with paper or string. In 1901, chemist Mikhail S. Tsvet used chromatography to isolate chlorophyll in plants. Today, we will use chromatography to learn what marker ink is made of.

  • Preparation

    1. Fill a container with water from the sink
    2. Draw a large dot or a ring in the middle of the bottom of the coffee filter using one color of marker
  • Procedure

    1. Make a prediction. How will dipping the coffee filter in water affect the ink on the coffee filter?
    2. Place the bottom inch of the coffee filter in the water but leave the rest of it dry. 
    3. Observe what happens to the marker ink on the coffee filter.
    4. Try again with a different color or pattern and see if things change or stay the same. Remember to only change one variable at a time to make sure you get good results.
  • Observation and Result

    You should see the water move up the coffee filter and the different colors in the ink start to separate. There are two things working together to separate the colors from each other in the ink. First, the water and ink are flowing up the filter because of capillary action. The fibers in the coffee filter are packed close together so the water can flow up them just like the bristles on a paintbrush. 

    Second, the different densities of the dyes allow them to separate into different bands along the filter. As we learned earlier, chromatography is the separation of a mixture (our marker ink) by passing it in a solution (water) through a medium (coffee filter) in which the components of the mixture (the various colors that make up any given marker color) move at different rates.  

    In our experiment, as the water travels up the coffee filter, it carries the ink particles with it. Because the ink particles are a mix of lots of different colors, and the different colors have different densities, some are carried farther than others, so you can see the colors separate. Some colors are actually mixtures of lots of different inks, while some are just one or two inks mixed together. See if you can discover which colors make the best patterns. 

  • Clean Up

    Remember to clean up when you are done. Pour the water down the sink and wash the container. If you want to keep the coffee filters and use them to make an art project, or a decoration, you can certainly do so, or you can throw them away when you are done. 

  • More to Explore

    How often were you able to correctly guess what colors would show up based on the color of the marker? Were any marker colors more impressive than others? Why might they be different? Do you think that the same marker color but from a different brand of marker would give the same result, or a different one?

    Sometimes scientists need to separate things which are combined together, like you did with the inks in these markers. Can you think of or look up any times when it might be useful for them to use this same kind of method? Try to find or think of examples where a scientist might need to separate things that are combined, but where this method wouldn’t work. Why wouldn’t it work for those?

  • Safety First & Adult Supervision

    • Follow the experiment’s instructions carefully.
    • A responsible adult should assist with each experiment.
    • While science experiments at home are exciting ways to learn about science hands-on, please note that some may require participants to take extra safety precautions and/or make a mess.
    • Adults should handle or assist with potentially harmful materials or sharp objects.
    • Adult should review each experiment and determine what the appropriate age is for the student’s participation in each activity before conducting any experiment.

Next Generation Science Standard (NGSS) Supported - Disciplinary Core Ideas

This experiment was selected for Science at Home because it teaches NGSS Disciplinary Core Ideas, which have broad importance within or across multiple science or engineering disciplines.

Learn more about how this experiment is based in NGSS Disciplinary Core Ideas.

Physical Science (PS) 1: Matter and Its Interactions

Grades K-2

  • 2-PS1-1. Different kinds of matter exist and can be described by its observable properties.
  • 2-PS1-2. Different properties are suited to different purposes.

Grades 3-5

  • 5-PS1-1. Matter of any type can be subdivided into particles that are too small to see, but event then the matter still exists and can be detected by other means.

Grades 6-8

  • MS-PS1-1. Atoms form molecules that range in size from two to thousands of atoms. Molecules may be extended structures with repeating subunits.
  • MS-PS1-2. Each pure substance has characteristic physical and chemical properties that can be used to identify it.
  • MS-PS1-4. In a solid, atoms are closely spaced and may vibrate in position but do not change relative locations.

Grades 9-12

  • HS-PS1-1. Each atom has a charged substructure consisting of a nucleus, which is made of protons and neutrons, surrounded by electrons.
  • HS-PS1-2. The periodic table orders elements horizontally by the number of protons in the atom’s nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect pattern of outer electron states.
  • HS-PS1-3. The structure and interactions of matter at the bulk scale are determined by electrical forces within and between atoms.
  • HS-PS1-4. Stable forms of matter are those in which the electric and magnetic field energy is minimized.

PS2: Motion and Stability: Forces and Interactions

Grades K-2

  • K-PS2-1. Pushes and pulls can have different strengths and directions.
  • K-PS2-2. Pushing or pulling on an object can change the speed or direction of its motion and can start or stop it.

Grades 3-5

  • 3-PS2-1. Each force acts on one particular object and has both strength and a direction. An object at rest typically has multiple forces acting on it, but they add to give zero net force on the object. Forces that do not sum to zero can cause changes in the object’s speed or direction of motion.
  • 3-PS2-2. The patterns of an object’s motion in various situations can be observed and measured; when that past motion exhibits a regular pattern, future motion can be predicted from it.

Grades 6-8

  • MS-PS2-1. For any pair of interacting objects, the force exerted by the first object on the second object is equal in strength to the force that the second object exerts on the first, but in the opposite direction.
  • MS-PS2-2. The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

Grades 9-12

  • HS-PS2-1. Newton’s second law accurately predicts changes in the motion of macroscopic objects.
  • HS-PS2-2. Momentum is defined for a particular frame of reference; it is the ass times the velocity of the object. In any system, total momentum is always conserved.
  • HS-PS1-3. If a system interacts with objects outside itself, the total momentum of the system can change; however, any such change is balanced by changes in the moment of objects outside the system.

Grades K-2

  • K-PS2-1. When objects touch or collide, they push on one another and can change motion.

Grades 3-5

  • 3-PS2-1. Objects in contact exert forces on each other.
  • 3-PS2-3. Electric and magnetic forces between a pair of objects do not require the objects to be in contact.
  • 3-PS2-4. The sizes of the forces in each situation depend on the properties of the objects and their distance apart and, for forces between two magnets, on their orientation relative to each other.

Grades 6-8

  • MS-PS2-3. Electric and magnetic forces can be attractive or repulsive, and their sizes depend on the magnitudes of the charges, currents, or magnetic strengths involved and on the distance between the interacting objects.
  • MS-PS2-5. Forces that act at a distance can be explained by fields that extend through space and can be mapped by their effect on a test object.

Grades 9-12

  • HS-PS2-4. Forces at a distance are explained by fields permeating space than can transfer energy through space.
  • HS-PS2-5. Magnets or electric currents cause magnetic field; electric charges or changing magnetic fields cause electric fields.
  • HS-PS2-6. Attraction and repulsion between electric charges at the atomic scale ex plain the structure, properties, and the constant forces between material objects.

Grades K-2

  • K-PS2-1. A bigger push or pull makes things go faster.

Grades 3-5

  • 4-PS3-3. When objects collide, the contact forces transfer energy so as to change the objects’ motions.

Grades 6-8

  • MS-PS3-2. When two objects interact, each one exerts a force on the other that can cause energy to be transferred to or from the object.

Grades 9-12

  • HS-PS3-5. When two objects interacting through a field change relative position, the energy stored in the field is changes.