Chemistry - 0620 CIE

Water

Bayani Gaba-gaba

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.

Manufura

Describe chemical tests for the presence of water using anhydrous cobalt(II) chloride and anhydrous copper(II) sulfate.
Describe how to test for the purity of water using melting point and boiling point.
Explain that distilled water is used in practical chemistry rather than tap water because it contains fewer chemical impurities.
State that water from natural sources may contain substances, including: (a) dissolved oxygen (b) metal compounds (c) plastics (d) sewage (e) harmful microbes (f) nitrates from fertilisers (g) phosphates from fertilisers and detergents.
State that some of these substances are beneficial, including: (a) dissolved oxygen for aquatic life (b) some metal compounds provide essential minerals for life.
State that some of these substances are potentially harmful, including: (a) some metal compounds are toxic (b) some plastics harm aquatic life (c) s ewage contains harmful microbes which cause disease (d) nitrates and phosphates lead to deoxygenation of water and damage to aquatic life Details of the eutrophication process are not required.
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.

Takardar Darasi

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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Nazarin Darasi

Barka da kammala darasi akan Water. Yanzu da kuka bincika mahimman raayoyi da raayoyi, lokaci yayi da zaku gwada ilimin ku. Wannan sashe yana ba da ayyuka iri-iri Tambayoyin da aka tsara don ƙarfafa fahimtar ku da kuma taimaka muku auna fahimtar ku game da kayan.

Za ka gamu da haɗe-haɗen nau'ikan tambayoyi, ciki har da tambayoyin zaɓi da yawa, tambayoyin gajeren amsa, da tambayoyin rubutu. Kowace tambaya an ƙirƙira ta da kyau don auna fannoni daban-daban na iliminka da ƙwarewar tunani mai zurfi.

Yi wannan ɓangaren na kimantawa a matsayin wata dama don ƙarfafa fahimtarka kan batun kuma don gano duk wani yanki da kake buƙatar ƙarin karatu. Kada ka yanke ƙauna da duk wani ƙalubale da ka fuskanta; maimakon haka, ka kallesu a matsayin damar haɓaka da ingantawa.

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