Quality of Water Essay

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SCIENCE SCIENCE Water Quality Water Quality KS4 KS4 Chemistry Chemistry | | Student Name Student Name SC20 SC20 This Study Pack aims to cover: 1. Hardness of water 2. Water treatment. This Study Pack aims to cover: 3. Hardness of water 4. Water treatment. | Contents | Water Quality Notes | 2-5 | Practice questions | 6-15 | Exam questions | 16-26 | Mark scheme | 27-32 | WATER TREATMENT Hard as ion support worksheet 1 Aims The water that comes from a tap is not pure. It has many substances dissolved in it. Sometimes the ions dissolved in the water make it hard. Hard water has some benefits and some disadvantages. In this task you will review your understanding of what hard water is and the difference between permanent hardness and temporary hardness. Questions 1 Water is said to be hard when it contains two particular ions. One is calcium ions, Ca2+. Which is the other ion? Highlight the correct ion. Li+ Fe3+ Cl− Mg2+ O2− 2 Water can have ‘permanent’ or ‘temporary’ hardness. Which type of hard water forms scale (limescale)? 3 What do you have to do to hard water to cause it to form scale? 4 Having hard water may mean you need to add more soap powder to a washing machine. The scale can coat the heating element, which heats the water. Why can it be expensive if the heating element gets coated in scale? 5 Hard water may have some health benefits. Why might people with brittle bones be encouraged to drink hard water? (Hint: check Question 1.) Figure 1: Diagram of an ion-exchange column An ion-exchange column is used to soften water. The resin beads inside the column are covered with sodium ions. The resin works by exchanging the ions in the hard water for sodium ions. 6 The resin softens the water when the hard water ions are swapped with

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