Introduction
Chromatography is a
technique used to separate mixture into its individual components.
This method is
commonly used to test ink, food colouring, and other coloured substances. It is
widely used in a crime scene investigation. There are several types of
chromatography, but we will only discuss paper chromatography.
Activity 1: Food
Colouring
Objective: to test
mixture of colours in food colouring
Steps:
1.
Draw
a line on a rectangular filter paper about 1.5 cm from the bottom by using
pencil
2.
Put
one drop of each food colouring (red, blue and green) on the line by using
toothpick
3.
Pour
20 ml distilled water into the beaker
4.
Dip
the filter paper in the beaker and hang it by using toothpick
5.
Make
sure the pencil line is above the water level.
6.
Wait
10-15 minutes
7.
Record
your observations.
Results &
Observation:
Red colour shows
slightly orange at the top
Blue colour shows
slightly purple
Green colour separates
into blue and yellow
Discussion &
conclusion:
Red food colouring
shows the purest red colour, while green colour is a mixture.
Activity 2: Permanent
marker
The steps are the same
with Activity 1, only change the food colouring to marker.
We use 3 different
colours (red, blue and black) from 3 different brands of markers.
From the results, the
ink which traveled the highest is the most soluble in water.
Oppositely, the lowest
distance traveled by the ink shows the ink is less soluble in water. So, buy
that brand. You don’t want your writing easily wash away if it comes in contact
with water, do you?
As for the mixture of
colours, you have to test for yourself, as different marker gives different
result. You may be surprise with the result.
Activity 3: Detective
Play
I ask the students to
draw a group symbol. It is hidden from other groups.
Each of the symbols is
then put into an envelope.
Next, one group take
one envelope (make sure they don’t get their own).
Now, they have to find
out the owner of the symbol by testing the ink of the marker used.
Investigation steps:
The students get the
sample ink from the note. They use the chromatography technique.
The result is then
compared to the ink results from previous activity.
They should be able to
find out the brand of the marker used and then name which group owns the
symbol.
Result:
Out of 6 groups, 4
groups of students are able to state the correct owner of the symbol.
The fastest group with
the correct answer is the winner.
Download the
materials:
No comments:
Post a Comment