A complete mind map with information about chromatography using filter paper and gas to separate substances.
Tom Johnson
Mind Map by Tom Johnson, updated more than 1 year ago
Tom Johnson
Created by Tom Johnson over 9 years ago

Resource summary

  1. Chromatography is used to identify substances in a mixture/sample
    1. Gas Chromatography
      1. How Does it Work?
        1. 1) A gas is used to transport substances through a column packed with solid metal
          1. 2) The substances (compounds) travel at different rates through the metal column and are separated out during the journey
            1. 3) The substances all reach a detector at the end of the metal column at different times
              1. 4) The time taken for the substances to get to the detector from entering the column is called the "retention time"
                1. 5) A recorder in the detector creates a graph with the x axis measuring time. Every time a new substance reaches the detector, it creates a peak on the graph
                  1. 6) This graph is called a "gas chromatograph" and the number of peaks shows the number of different compounds in the sample
                    1. 7) The position of the peaks on the graph shows the retention time for each substance
        2. What Does it Do?
          1. Gas Chromatography is used to separate out and identify a mixture of compounds when moving through a gas and identify the substances present
        3. Chromatography Using Filter Paper
          1. What Does it Do?
            1. Chromatography using filter paper is used of commonly separating out substances in a sample, commonly artificial colourings. Eg. a food colouring might contain one dye or a mixture of dyes. Chromatography will help separate out these dyes
            2. How Does it Work?
              1. 1) A pencil baseline is drawn onto a strip of filter paper with a drop of food colouring (or choice of sample) placed upon this baseline
                1. 2) The filter paper is then rolled up and placed in a beaker with the water of solvent of choice only just touching the filter paper. The baseline is to be kept above the water level
                  1. 3) The solvent will then seep up the filter paper, bypassing the baseline and taking the dyes from the baseline with it
                    1. 4) The mixture of dyes will then begin to separate due to the different dyes absorbing into the filter paper at different rates (heights on the filter paper)
                      1. 5) The filter paper is then known as a "chromatogram" and displays the different dyes on it due to the different colours at varying heights up the filter paper
                        1. 6) A chromatogram with 4 spots means AT LEAST 4 different dyes, not EXACTLY 4 different dyes due to there being the possibility of multiple dyes absorbing in the same place
                2. How to Work Out the "Rf" Value for Each Chemical (Substance)
                  1. Rf= Distance Travelled By Substance (Eg. Food Colouring) ÷ Distance Travelled by Solvent (eg. Water)
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