Science - Combined - 0653 CIE

Water

Overview

Water looks simple, but the water that reaches your tap has been tested, treated and cleaned, and the water in a river carries a hidden cargo of dissolved gases, minerals and pollutants. Chemistry gives us the tools to test water for purity, to identify it, and to make it safe to drink.

In this lesson you will learn the chemical tests for water and the physical tests for its purity, why distilled water is used in the laboratory, what natural water may contain (the good and the harmful), and the three stages of treating a domestic water supply: filtration, removing tastes and odours, and chlorination.

Objectives

[Core] Describe chemical tests for the presence of water using anhydrous cobalt(II) chloride and anhydrous copper(II) sulfate
[Core] State that distilled water is used in practical chemistry rather than tap water because it contains fewer chemical impurities
[Core] Describe the treatment of the domestic water supply in terms of: (a) sedimentation and filtration to remove solids (b) use of carbon to remove tastes and odours (c) chlorination to kill microbes

Lesson Note

Clean water is essential to life, and unsafe water spreads disease. Understanding how to test water and how a public supply is treated is chemistry with a direct human impact, and it brings together ideas about purity, solubility and reactions you meet elsewhere in the course.

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Lesson Evaluation

Congratulations on completing the lesson on Water. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

What colour change shows water using anhydrous cobalt(II) chloride? A. white to blue B. blue to pink C. pink to blue D. blue to white Answer: B
Pure water boils at: A. 0 C B. 50 C C. 100 C D. 110 C Answer: C
Why is distilled water used in practical chemistry rather than tap water? A. it is cheaper B. it contains fewer chemical impurities C. it boils faster D. it is already chlorinated Answer: B
Which substance in natural water is beneficial? A. sewage B. plastics C. dissolved oxygen D. excess nitrates Answer: C
Which stage of water treatment kills harmful microbes? A. sedimentation B. filtration C. carbon treatment D. chlorination Answer: D