On Tuesday, Otober19, we did an experiment involving 3 food colourings, strips of paper, thin paper chromatography, and patience!
First we cut up a 66cm strip of paper into 3 strips of 22cm and cut one end of each strip into a point. Next we spotted the strips with a dot of food colouring each. One had a yellow spot, one had a green spot and the last one had an unknown coloured spot. Then we placed the strips (with the points facing downwards) into three test tubes containing water about 2cm high. This is where the patience comes in. We waited as the capillary action took place. It took a while but we observed that each spot started to dissolve. But after about 20 minutes, the dots had actually travelled up the strip as the water travelled up the strip also. For the yellow dot, there was no colour change. But the green dot eventually changed into yellow and blue (its component colours) and the unknown dot changed to red, yellow and blue. We then took out each strip and recorded the d1 which is the distance travelled by the solute or food colouring. We also recorded the d2 which is the solvent front or the distance travelled by the water. The class results were also recorded and we then calculated the Rf values using this equation:
Rf = d1/d2
The following picture is what our chromatography strip essentially looked like:
Click here for more detail on paper chromatography:
http://en.wikipedia.org/wiki/Paper_chromatographyHere is another way you could perform this experiment:
http://www.youtube.com/watch?v=fLc36wxLrVI&feature=relatedOn Thursday, October 21, we had our Chapter 1 and 2 test!
