{"id":245792,"date":"2024-11-11T16:00:49","date_gmt":"2024-11-11T08:00:49","guid":{"rendered":"https:\/\/thepiquelab.com\/blog\/?p=245792"},"modified":"2026-02-13T11:32:19","modified_gmt":"2026-02-13T03:32:19","slug":"separation-techniques-how-to-find-pure-substances-through-chromatography","status":"publish","type":"post","link":"https:\/\/thepiquelab.com\/blog\/separation-techniques-how-to-find-pure-substances-through-chromatography\/","title":{"rendered":"Separation Techniques: How To Find Pure Substances Through Chromatography"},"content":{"rendered":"

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Introduction<\/strong><\/p>\n

Do you find drawing conclusions from the results of a chromatogram challenging?<\/p>\n

In this Chemistry blog post, I will draw similarities between paper chromatography and a track race to help you understand key concepts of paper chromatography better.<\/p>\n

You can also watch our explainer video<\/a> on The Pique Lab\u2019s YouTube channel for free!<\/p>\n

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Read Also:<\/h3>\n
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  1. [Secondary 1 Science Explainer Video] Separation Techniques: How To Analyse 4 Dyes On A Chromatography<\/a><\/strong><\/li>\n
  2. Solutions & Suspensions: How Is Solubility Tested In Chemistry Examinations<\/strong><\/a><\/li>\n<\/ol>\n<\/div>\n

    Let’s Take A Look At This Chemistry Question<\/h2>\n

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    Source: Chua Chu Kang Secondary School \u2013 2020 Chemistry S1E SA2 Examination Paper [Q13]<\/span><\/em>
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    Let us begin by defining a chromatogram.<\/p>\n

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    \ud83d\udd0e\u00a0What Is A Chromatogram? \ud83d\udd0e<\/strong><\/p>\n

    A chromatogram is the result of a paper chromatography<\/strong> \u2014 a separation technique used to separate and identify small amounts of substances<\/strong> that are dissolved in a solvent<\/strong>. We can also use it to test the purity of a substance.<\/p>\n<\/blockquote>\n

    Let us look at the results of the chromatography.<\/p>\n

    What is the highest solvent level labelled in the diagram below?<\/p>\n

    If we were to compare it with a race, the highest solvent level is like the finishing line.<\/p>\n

    Meanwhile, the part I labelled in purple is the start line of the race.<\/p>\n

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    The start line is where I will put a tiny drop of the sample, just like what you see in F.<\/p>\n

    This chromatography paper is dipped into the solvent and the solvent moves up the paper, just like how racers run towards the finishing line.<\/p>\n

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    If the sample is made up of two or more components, the different components will move at different speeds together with the solvent and they will start to separate.<\/p>\n

    Let\u2019s take a look at the results.<\/p>\n

    Let’s Analyse Dye E<\/h2>\n

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    How many spots do you see for E?<\/p>\n

    There are two spots! This means that E is made up of two components, which are separated to form two visible dots on E.<\/p>\n

    Let us compare the two dots. What can we say about spot X below? It is closer to the finishing line.<\/p>\n

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    Do you think it moved faster or slower?<\/p>\n

    Since it is closer to the finishing line, it means that it moved faster<\/strong> and its component is more soluble<\/strong> in the solvent.<\/p>\n

    Let us take a look at spot Y, which is further away from the finishing line.<\/p>\n

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    Is spot Y more soluble or less soluble?<\/p>\n

    Since it is further away from the finishing line, it has moved slower<\/strong> in the solvent and is less soluble<\/strong> in the solvent.<\/p>\n

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    Let’s Analyse Dye F<\/h2>\n

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    Dye F has only one dot.<\/p>\n

    Does it mean that it is only made up of one component? No!<\/p>\n

    You\u2019ll notice that the dot is still on the start line and has not moved up together with the solvent.<\/p>\n

    We can compare it with a runner who did not run the race and just stayed at the start line.<\/p>\n

    Since F did not move with the solvent, it is insoluble<\/strong> in the solvent.<\/p>\n

    Hence, giving no results.<\/p>\n

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    Let’s Analyse Dye G<\/h2>\n

    How many components is dye G made of?<\/p>\n

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    Since we can only see one dot, this means that it is made up of only one component and is not mixed with any other substance.<\/p>\n

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    Let\u2019s Analyse Dye H<\/span><\/h2>\n

    Like dye E, dye H is also made up of two components since we can see two dots.<\/p>\n

    Let us label them!<\/p>\n

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    Thought Process<\/h2>\n

    Now that we\u2019ve analysed the results of the chromatogram, let\u2019s review the question.<\/p>\n

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    Source: Chua Chu Kang Secondary School \u2013 2020 Chemistry S1E SA2 Examination Paper [Q13]<\/span><\/em><\/p>\n

    We are looking for the dye, which is a pure substance<\/strong>.<\/p>\n

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    \ud83e\udd14\u00a0What Is A Pure Substance? \ud83e\udd14<\/strong><\/p>\n

    A pure substance is made up of only one component<\/strong> and cannot be mixed with other substances.<\/p>\n<\/blockquote>\n

    Let\u2019s take a look at our chromatogram.<\/p>\n

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    How many dots should we look for in the chromatogram?<\/p>\n

    We should look for the chromatogram with only one dot that has moved up the solvent.<\/p>\n

    Which result shows us that there is only one component in the dye?<\/p>\n

    It is dye G<\/strong>!<\/p>\n

    Answer For Q13<\/h2>\n

    Option (3)<\/p>\n

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    Conclusion<\/h2>\n

    I hope that after reading this Chemistry blog post, you will remember the following key points when analysing a chromatogram:<\/p>\n