5405952
Description
Flashcards by Anisha Rai, updated more than 1 year ago
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Created by Anisha Rai
almost 8 years ago
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| Question | Answer |
| What does natural water contain? | Dissolved salts which can be removed to obtain pure water |
| How can pure water be made? | By distillation |
| What is desalination? | An important method of obtaining water for domestic use in some countries |
| What is the boiling point of pure water? | 100 degrees Celsius |
| Give a simple chemical test to show the presence of water | Pure copper(II) sulphate is white. When water is present in a sample of copper(II) sulphate it turns blue. This colour change can be used to detect the presence of water (or water vapour). |
| What level of dissolved salts and microbes should there be in drinking water? | Sufficiently low |
| How is water of the correct quality produced? | By passing a suitable source through filter beds to remove solids, and then sterilising with chlorine |
| What do water filters contain that can remove some dissolved substances from tap water and improve taste and quality? | Carbon, silver and ion exchange resins |
| How do ion exchange resins work? | The resin beads have sodium ions attached to them. As the hard water passes through the column, the calcium and magnesium ions swap places with the sodium ions. The calcium and magnesium ions are left attached to the beads, while the water leaving the column contains more sodium ions. The hard water is softened because it no longer contains calcium or magnesium ions. Some ion exchange resins use hydrogen ions instead of sodium ions. |
| What are the argument FOR the addition of fluoride to drinking water | Dental health improves Fluoride addition is sometimes viewed especially important in low-income areas, where access to non-water sources of fluoride (such as toothpastes) is limited to residents |
| What are the argument AGAINST the addition of fluoride to drinking water | People have no choice in taking fluoride if it is in their water supply Consumption at higher levels over time has been proven to cause painful bone disease |
| Why might chlorine be added to drinking water? | To reduce microbes |
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