Water
| English | Chinese | Pinyin |
|---|---|---|
| water treatment | 水处理 | shuǐ chǔ lǐ |
| filtration | 过滤 | guò lǜ |
| chlorination | 氯消毒 | lǜ xiāo dú |
Pure enough to drink
- Clean water is essential for life, but natural water is full of dissolved and suspended substances.
- Making it safe involves water treatment 水处理 and testing.
Water treatment lab
Classify water processes by what they remove or change.
Chlorine is added during water treatment to:
Chlorination sterilises the water.
Filtration removes solid particles from water.
It removes insoluble solids.
Water treatment
- Filtration 过滤 removes solid particles.
- Chlorination 氯消毒 (adding chlorine) kills harmful microbes (sterilisation).
Treating water to make it safe to drink: sedimentation, filtration, carbon, then chlorination
Anhydrous copper sulfate turns which colour in the presence of water?
White anhydrous copper sulfate turns blue with water.
Cobalt chloride paper turns from blue to ______ in the presence of water.
A test for the presence of water.
Testing for water
- To test that a liquid is water: it turns anhydrous copper sulfate from white to blue, or cobalt chloride paper from blue to pink.
- To test it is pure water: it boils at exactly 100 °C and freezes at 0 °C.
At what temperature (°C) does pure water boil at normal pressure?
Pure water boils at exactly 100 °C.
"Is water" vs "is pure"
- A chemical test shows a liquid contains water.
- Only the boiling/freezing point shows it is pure water (no dissolved substances).
"Contains water" is not the same as "pure water". Sea water turns cobalt chloride paper pink (it contains water) but is far from pure. Purity is shown by a sharp boiling point of 100 °C.
You've got it
- water treatment: filtration (removes solids) + chlorination (kills microbes)
- test for water: anhydrous copper sulfate white → blue, or cobalt chloride blue → pink
- only the boiling point (100 °C) shows water is pure