A sample of water was contaminated with a dissolved solid. Devise a plan to separate pure water from this mixture, including a test to show that the water obtained is neutral. You may use some or all of the apparatus shown in Figure 11 and any other laboratory apparatus – 9014

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1. To separate pure water from a solution, you use simple distillation. First, pour the solution into a flask and heat it using a Bunsen burner. As the solution heats up, the water starts to evaporate because it has a lower boiling point than the dissolved solid. When the water boils, it turns into water vapour and travels through a condenser.

   The condenser has a cooling water jacket around it, which helps the hot water vapour to cool down and condense back into liquid water. This liquid water then drips into a clean beaker and is collected. The solid that was dissolved in the water stays behind in the flask, because it does not evaporate. The boiling point of pure water is 100°C, so heating it to this point ensures that only water evaporates.

   To test the purity of the water collected, pour a small amount into a test tube. Then, add a few drops of universal indicator or neutral litmus solution. If the water is pure, it will show a neutral colour, such as green with universal indicator. Alternatively, you can test the water using a pH probe. If the water is pure, the pH should be 7, showing that it is neutral

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