Water Flashcards
Describe the test that can be carried out to test for the presence of water
Cobalt chloride paper turns from blue to pink in the presence of water
Name the two elements that make up a compound of water and give the composition
Hydrogen and oxygen , 2 hydrogens and 1 oxygen
What is soft water ?
Water that easily forms a lather with soap.
What is hard water ?
Water that does not easily form a lather with soap .
What causes hardness?
The presence of calcium ions dissolved in the water
How can hardness be removed ?
By passing the water through an ion exchange resin
Give the two advantages of hard water
1) good source of calcium for strong bones and teeth
2) hard water taste better than soft water
Give the two disadvantages of hard water
1) wastes soap and leaves a scum
2) limescale blocks pipes and reduces the efficiency of kettles and washing machines
What is the boiling point for water ?
100C
What is the freezing point for water ?
0C
Name the five stages for the treatment of water( Sabrina screamed for clothing funds )
Screening Settling Filtration Chlorination Fluoridation
Describe screening
Removes large debris by passing water through a wire mesh
Describe settling
Aluminium sulphate is added to the water , it makes the particles stick together
Describe filtration
Very small dirt particles are removed through filtration
Describe fluoridation
In Ireland fluorine is added to prevent tooth decay
How does an ion exchange resin remove hardness
It replaces the ions in the hard water that cause hardness with ions that dont . The water then becomes soft water or deionised water
What is electrolysis ?
The production of a chemical reaction through electricity
What is a Hoffman voltameter ?
It is used to pass a current through water causing it to break down into hydrogen and oxygen
Why is sulfuric acid added to water ?
To help it to conduct electricity
What is the test for hydrogen ?
It burns with a ‘pop’
What is the test for oxygen ?
Relights a glowing splint
Why is there twice as much hydrogen than oxygen produced ?
Because each water molecule has two hydrogens atoms for every oxygen atom
Describe a test that distinguishes between hard and soft water
1) pour water from the various samples into different test tubes
2) make sure to use the same amount of water in each test tube to make it a fair test
3) add the same number of soap flakes to each test tube to also make it a fair test
4) shake the mixture
5) explain what test tube forms a lather
6) a lather will form in the test tube containing soft water and no lather will form in the test tubes containing hard water
