Page 57 - Big Ideas Year 9 sciPAD 2025

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SCIPAD - BIG IDEAS - BOOK 1
THE NATURE OF MIXTURES
(a) Name the pens that contain only one pigment. 

(b) Green is made by mixing blue and yellow. Did the manufacturer use the pigment
from the light blue marker, the dark blue marker or a different blue pigment? Justify
your answer. 


(c) How many different red pigments were used in the 8 marker pens? 
(d) Did the manufacturer use the same yellow in the orange and green marker pens?
Justify your answer. 

(e) Which of the pigments used in making the pens is the least soluble in water? 

8. Someone has drawn graffiti on your sciPAD! You
share a bench with four others. You take an ink
sample from the graffiti and from the pens of
the four suspects. Using chromatography, you
separate the pigments in the ink samples. The
chromatogram on the right shows the results of
your investigation.
Which suspect most likely drew the graffiti?
Justify your answer. 


5. Why should the ‘start line’ always be drawn in pencil? 

6. Explain why the solvent level must be lower than the sample spots on the filter paper. 

7. The chromatogram below was obtained using a set of felt-tip pens and water as the
solvent. (Note: Spots of the same colour and same height can be assumed to be the same
substance.
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