Evaporation

Transcript

What is Evaporation?Evaporation is the process in which a liquid gets converted into its vapour. It can be used to separate a solid dissolved in a liquid. How can Evaporation be used in Separation? If we take a solution of water and salt and evaporate it then water will disappear and only salt will remain. Activity 9.2Take a bowl or any container and fill it half with water. Add 2–3 teaspoons of salt into it and stir till the salt dissolves to form a solution. Take a small piece of black or dark coloured thick paper and spread a few drops of the salt solution on it. You can also create any art of your choice with this salt solution. Allow it to dry and then observe it. Salt is left behind Activity 9.3Take some salt solution (prepared in Activity 9.2) in a china dish. If a china dish is not available, another suitable vessel may be used. Heat and let the water boil away. Allow the china dish to cool down. What do you observe? What is left in the china dish? Observation We observe that the water is evaporated and the salt is left behind. Is there a method in which we can get both Salt and Water?Yes, by the method of distillation, both salt and water can be obtained from salt water. We take Salt and Water Solution in a Kettle We heat it and keep a plate near the mouth of the Kettle Salt left in the Kettle and water get collected in beaker Water Vapour cools down to form Water which gets collected in beaker Practical use of Evaporation River Water (We can Drink it) Sea Water (We Can’t drink it, as it is too Salty) We Separate Salt from it How is Salt (Namak) obtained from Sea Water?Sea Water put in Shallow Pits Exposure to Sunlight This Salt purified and impurities removed Water Evaporates and Solid mixture remains containing mainly Salt What does Evaporation do?Salty Water Heat Sunlight converts Water to Water Vapour Salt (This we purify and use)