Chapter 28 - Water Flashcards
What is water?
Water is a compound made up of hydrogen and oxygen
What are the 4 stages of the water cycle?
- Evaporation
- Condensation
- Precipitation
- Run-off
What are the stages of water treatment?
- Screening
- Settling
- Filtration
- Chlorination
- Fluoridation
What is involved in screening?
Passing water through a wire mesh or screen to remove any floating material
What is involved in settling?
Water flows into large tanks and the chemical ‘aluminium sulfate’ is added. This causes small insoluble particles to come together and settle at the bottom of the tanks
What is involved in filtration?
Water is passed through beds of sand.Any remaining insoluble particles are removed.The water is now clear in colour but may contain bacteria.
What is involved in chlorination?
Chlorine is added to the water to kill any bacteria present. The amount added is carefully monitored
What is involved in fluoridation?
Fluorine is added in some countries to prevent tooth decay
Water turns cobalt chloride paper from,…
…blue to pink
Water turns anhydrous copper sulfate from,…
…pale blue to bright blue
Electrolysis
The splitting up of a compound by passing electricity through it
What piece of apparatus can be used to electrolyse water?
A Hoffman voltameter
Why is a small amount of acid added to water during electrolysis?
Pure water is a poor conductor of electricity, so a small volume of dilute sulfuric acid is added to improve its conductivity
What is the chemical formula of water? What does this mean?
Water has the chemical formula H2O. When split the molecule releases two hydrogen atoms for every one oxygen atom
Meniscus
The curved surface of a liquid in a vessel
