This experiment is to determine whether a physical change or chemical change has taken place when a piece of paper with ink dot is pour into chromatography fluid. Chromatography is a process used to separate mixtures. The word chromatography originated from the Greek words “Khroma” and “Graphein” meaning “colour” and “to write” or “to represent”.
APPARATUS AND SUBSTANCE USED ARE AS FOLLOWS
- Chromatography paper
- Ink dot
- Boiling tube
- Chromatography fluid (is a combination of Ammonia×1+Ethanol ×1 + Butanol ×3
- Scissors
METHODS
A piece of chromatography paper was cut about 1.5cm×160cm in size, then a pen was used to supplied a dot ink onto the paper a few times in the bottom part of the paper as you held it up with you hand, when the ink has dried pour a little chromatography fluid into a boiling tube then place in a stand, then the paper was place into the tube and fold over the top edge so that the paper hangs vertically .The content was left for half an hour.
(a) Before
RESULT
(b) After
It was witnessed that the dot spot on the paper increase in volume and expand on a straight line with different colours like rainbow, it changes from black colour to orange colour which stays at the bottom then to blue, pink and purple respectively, the speed of travel is slower in orange while the speed of purple is much faster.
CONCLUSION
This experiment shows that different dye travel at different rate through the chromatography paper when a current of water flows through it. Some dye molecules partition themselves in two phases in a particular proportion, example some dye molecules attach strongly to the wet fibre so that at the surface of a fibre, 90% of dye molecules attach to the fibre and 10% of them in water, and some molecule will distribute themselves 50% on fibre and 50% on water.
This is a physical change because the molecules of colour can be separated; they are mixture rather than being chemically combined. Some colour molecules cling hard, while others are weak held to the paper, those that are weakly held travel further up the paper and spread further than those with the stronger bond.
- This technique has been used in forensic and medical profession.
- It is commonly used in laboratories to isolate new compounds, analyse subtle differences between different environmental samples, and even in the sequencing of DNA.
- Chromatography is used to detect, separate, or purify different substances. Using this process in food, drugs, blood, soil, water, air, fuel and petroleum and radioactive-fission products are analysed.
- In medical field, chromatography can determine the presence of drugs in a person’s blood. In water and air quality analysis chromatography is used to isolate pollutants.
