Separation Techniques – Filtration and Chromatography
Materials:
SOLVENTS: Water
SOLUTES:
Salt and Sand
Coffee Filter Paper, Cups and spoons
INTRODUCTION
Studying chemistry, the science of matter. One of the most important aspects of chemistry is separation of
mater. Mixture of substances into two or more distinct products. Oil to gas. Purification of metal from dirt
 Iron, Copper
DEMONSTRATION AND DISCUSSION IN SMALLER GROUPS
Demonstration Filtration – Sand and Water
Q. Does sand dissolve in water?
A. No
Q. How can we separate sand and water mixture?
A. Filtration
Perform filtration by using coffee filter and pour sand and water mixture.
Q. What does filtration separate?
A. Solid from liquid
Demonstration Separation Filtration – Salt and Sand
Q. Can we use filtration to separate salt and sand (two solids)?
A. No. Cannot separate two solids.
Perform filtration of salt and dry sand. Salt and Sand still mixed.
Q. How can we separate salt and sand? (Hint: Remember Solubility)
A. Salt dissolves in water. Then filter mixture.
Demonstrate dissolving pure salt with water.
Q. What happened to the salt?
A. Salt dissolved into water.
Q. How do we know?
A. Matter cannot disappear has to go somewhere. (Kids can taste water if they want)
Q. Can we separate water, salt, and sand mixture?
A. Yes can separate sand from water.
Add water to sand and salt mixture. Filter
Q. Where is the salt?
A. In the water. We call the salt a solute and the water a solvent. (Kids can taste if they want to)
Q. How can we separate salt and water?
A. Let water evaporate. (Will not do)
Separation Techniques – Chromatography
Materials:
SOLVENTS: Water with pinch of salt (0.1% salt by mass)
M&M’S
Whatman 1 filter paper, Cups, paint brush
HEALTH & SAFETY: Students must not attempt to eat the M&M’S or even lick them. They are for
laboratory use only.
While finishing discussion of filtration put one drop of water with paintbrush on top of each color M&M.
DEMONSTRATION AND DISCUSSION IN SMALLER GROUPS
What if everything is soluble in the mixture? How can we separate the components?
Tell kids that they cannot eat the M&Ms or even lick them. For laboratory use only.
Each M&M color is made out of either one or multiple dyes. How can we separate these dyes?
Chromatography – Separate soluble compounds from each other.
1. Place the piece of chromatography paper on a clean flat surface, with the shorter side horizontal
and draw a horizontal line in pencil (not biro) about 1.5 cm from the base of the paper.
2. Use the dampened paint brush to put 1 drop of water on top of each M&M. Let sit for at least
several minutes to remove the color. Wash brush and dry in extra paper. Use dry brush to paint
color from one of the M&M’S on the line about 0.5 to 1 cm from one end. Small spots are best.
3. Clean the brush in fresh running water then dry and paint the color of another M&M® on the line
about 1 cm from the first spot.
4. Repeat this until all the colors are on the paper or may need to use multiple sheets of paper.
5. Use a pencil to write the name of the color next to the corresponding spot.
6. Fold paper in thirds. Avoid folding on a spot.
7. Put water into the beaker up to depth of about 1 cm. Add pinch of salt and mix.
8. Lower the paper cylinder into the beaker of water thus allowing the water to rise up the paper.
Ensure that the water is below the level of the spots. Try to avoid moving the paper cylinder
about once it is in position.
9. When the water approaches the top of the paper cylinder remove it from the water. Mark with a
pencil the level of the water at the top of the filter paper
Encourage the students to make small intense spots on the paper and to avoid smudging.
Some dyes will be found to produce only one spot further up the paper, whilst others will have spread into
two or more areas of color.
If appropriate students should be told that the relative distance travelled by each “spot” depends not only
on its solubility in water but also on its attraction for the cellulose components of the paper.
Here are some questions for students.
a Why do you think some dyes separate out into different colors whilst others do not ?
b Why do you think some colors move further up the paper than others ?
d Look on the side of a M&M’S® packet for a list of the colored dyes used. Try to identify.
Red 40 (Red), Blue 1 (Blue), Blue 2 (Indigo), Yellow 5 (Yellow), Yellow 6 (Orange)