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Home learning activities Subject Science Year Group Year 8 Unit of work / Knowledge organiser Mixtures and Separation Techniques Activities • Read through Sections 1-7 of the ‘Knowledge Organiser’ on ‘Mixtures and Separation Techniques’. Make careful and detailed notes on sections 1-3 as well as writing a list of the separation techniques which are described in the remaining sections. • Without looking at your notes, describe, in your own words, what a mixture is (compare your answer with Section 1 afterwards). • Learn the meanings of the key words from the ‘Mixtures and Separation Techniques Keywords’ sheet and complete the key words from memory on the ‘Keywords Test’ sheet. Find your score using the ‘Key Words’ sheet. • Read the ‘Key Revision Facts’ sheet carefully. • Describe, in your own words, the difference between ‘filtration’, ‘distillation’ and ‘chromatography’ without looking at the ‘Key Revision Facts’ sheet. • Complete the ‘Match and Draw’, ‘Filtration’ and ‘Dissolving’ activities on the ‘Test Yourself’ pages; the answers are provided at the end, but do not look at these until you have tried to complete the work yourself (be strict with yourself here). • Complete the exam question on ‘Mixtures and Separation Techniques’. Use the mark scheme (once you have tried the question) to mark your answers carefully. Where do you complete the work? In Study Books. What to do if you finish the work? (Extension activity) • Make sure you have completed the previous set work on ‘Pressure and Moments’ and then complete the ‘Mini Project’ on ‘Separating Mixtures’. These websites might help: • BBC Bitesize -> Secondary -> KS3 -> Science -> Chemistry -> Separating Mixtures If you are struggling with your work or if you have finished. Please email your classroom teacher directly using the email list found in the Home Learning section of the website. Year 8 — Mixtures and Separation Techniques 1. What is a mixture? 4. Crystallisation A mixture consists of two or more different substances, not chemically joined together. The substances in a mixture can be elements, or compounds, or both. Being part of a mixture does not change the chemical properties of the substances that are in it. Examples of mixtures are: Sea water, air, soil and bleach. 2. Pure or Impure? A pure substance consists only of one element or one compound. An impure substance is made of two or more elements or compounds that are not bonded together chemically. 3. Solutions Mixture formed from a solvent and a solute. 5. Filtration Examples of solutions are: Filtration is a method for separating an Dishwater (soap dissolved in water) insoluble solid from a liquid. When a Fizzy drinks (carbon dioxide dissolved in water) mixture of sand and water if filtered, Sweet tea (sugar dissolved in solution) the sand stays behind in the filter paper (residue) and the water passes through the filter paper (filtrate) Year 8 — Mixtures and Separation Techniques 6. Distillation 7. Chromatography Distillation is a method for separating the solvent from a solution. For exam- Paper chromatography is a method for separating dissolved substances from ple, water can be separated from salt solution by simple distillation. This meth- one another. It is often used when the dissolved substances are coloured, od works because water has a much lower boiling point than salt. When the so- such as inks, food colourings and plant dyes. It works because some of the lution is heated, the water evaporates. It is then cooled and condensed into a separate container. The salt does not evaporate and so it stays behind. coloured substances dissolve in the solvent used better than others, so they travel further up the paper. A pure substance will only produce one spot on the chromatogram during paper chromatography. Two substances will be the same if they produce the same colour of spot, and their spots travel the same distance up the paper. In the example below, red, blue and yellow are three pure substances. The sample on the left is a mixture of all three.
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