Sciences - Co-ordinated (Double) - 0654 CIE

Water

Gbogbo ọrọ náà

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.

Ebumnobi

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.

Akọmọ Ojú-ẹkọ

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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Ayẹwo Ẹkọ

Ekele diri gi maka imecha ihe karịrị na Water. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

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