Science - Water Flashcards
What is hardness in water caused by?
It is caused by calcium ions
Name the five stages of water treatment and explain each stage.
Screening - wire screens trap large rubbish
Settling - water is left in large tanks where large solids settle to the bottom. Cleaner water is pumped off at top
Filltration - all the solids are removed by passingthe water through filter beds
Chlorination - chlorine is added to kill bacteria
Flourination - a chemical is added to water to prevent dental decay
Explain the forming of a lather on hard and soft water.
Soft water forms a lather easily.
Hard water does NOT form a lather easily.
Name two advantages and two disadvantages to hard water.
Advantages: tastes nicer, contains calcium for stronger bones
Disadvantages: causes limescale-blocks pipes, forms a scum
How is hardness in water removed?
Hardness can be removed by exchanging calcium ions with ions that don’t cause hardness or by distillation.
What is the softest and hardest form of water?
Distilled water is the softest and seawater is the hardest.
What is electrolysis?
It is splitting compounds into their elements by passing and electric current through them.
Name three unusual properties of water.
It expands when frozen instead of contracts, it has water tension which is a type of skin on top of the water, it is denser than ice.
What is a meniscus?
It is a curved surface of any liquid.
What is desalination?
It is the removal of salt from seawater to form freshwater.
