Learn to separate mixtures using the method of chromatography!
With this experiment you can explore the different components of a mixture.
What is Chromatography?
Chromatography separates components from mixtures. Each component has a unique separation rate which can be used to identify different components in a mixture.
By using chromatography, we can find out all the different components a mixture is made of.
This method was discovered by Mikhali Tsvet, who separated colour pigments of plants!
The experiment below uses the method of chromatography. Let’s dive in!
Exploring STEM Concepts in Chromatography
Here are some key concepts related to chromatography that will be helpful to understand before you conduct your experiment.
Cohesion
Cohesion is the process by which particles that are the same stick together. For example, water molecules sticking to other water molecules.
Adhesion
Adhesion is the process by which particles that are not the same stick together. For example, water molecules sticking to a paper towel.
Capillary Action
The ability for a liquid, like water, to move up something solid, like a tube or into a material with lots of holes. This happens with the help of three forces called cohesion, adhesion, and surface tension.
Surface Tension
An effect where the surface of the liquid is strong. Water molecules are more closely bound together at the surface, meaning that the top of the water will be tighter. During capillary action, surface tension will hold the water together at the top!
Materials
- 5 clear glass cups
- 5 coffee filters
- Washable markers (Red, black, brown, green, and blue)
- Water
- Paper
- Writing utensil
How to Do The Chromatography Experiment
Step 1
Flatten a coffee filter. Choose one colour and draw a circle around the middle of the filter. Repeat with the other colours and the coffee filters.
Make sure to draw identical sized circles onto your coffee filters!
You should have five coffee filters each with a different coloured circle drawn on them!
Step 2
Fold your coffee filters in half.
Now fold it again.
Fold it again one last time so that it forms a thin triangle.
Step 3
Pour a small amount of water into each of your glasses.
You want to have enough water in the glass so that it will be able to travel up the coffee filter but not too much that the lines drawn on your filters will be directly in the water.
Step 4
Make a prediction: What do you think will happen when you place your filter in the water? Will all of the colours behave the same way? Jot down your predictions!
Unfold the filter papers all the way and put the papers into the glass cups with water. Be sure that the coloured lines do not go directly into the water. Observe your experiment and jot down what you see!
Were your predictions correct? What happened to each of the colours when the filter paper was placed in water?
The colours should have separated into different pigments that make up that colour!
Try This Twist on the Experiment
Experiment with other types of markers to see if you can separate the colours into their different components.
Try felt tipped markers, permanent markers, dry erase markers, etc.
Be sure to make predictions for each marker type you choose to test!
Why Did Some Colours Spread Further Than Other Colours?
Pigments from the markers separated based on how big or small the pigment molecules are and how strongly the pigment molecules are attracted to the filter paper.
If the pigment molecules are small, they will travel faster.
If the pigment molecules are more strongly attracted to the filter paper the colour will also travel faster.
Yeast acts as a catalyst because there is a certain enzyme in yeast called catalase. Enzymes are proteins that act as catalysts, thus quickening the speed of reactions. Catalase is very common and can be found in almost all living organisms when exposed to oxygen.
How Do the Colours Rise?
The water soaks the paper evenly taking the colours with it. This is known as the capillary effect or capillary action. The colours rise at different speeds because the dyes in the mixture interact differently with the water and filter paper.
