Water (T2)

Question 0

What is an “ion exchange resin”?

Answer 0

Some filters contain ‘activated ingredients’ like carbon and silver. These attract some of the dissolved substances within water by clinging to the filter and not passing through, despite the atoms being a lot smaller than the gaps of the filter.

An advanced form of one of these filters is called an ion exchange resin.

They look like tiny beads and each bead has tiny “pores” on the surface that trap and release different ions.

In water purification, sodium or potassium ions might be released while the beads absorb the ions of copper and nastier chemicals that could harm the drinker.

Question 1

How is pure, drinkable water obtained?

Answer 1

Normally, pure water can be obtained by distillation.

One of the cheapest and best ways for a long term supply is an advanced form of filtration.

• water from a source (eg: reservoir) is exposed to a flocculation agent
• this causes the small materials to cluster and sink to the bottom of the reservoir
• these act as a coagulant for all of the larger solids found within the water drawn from the primary source
• it is then passed through several filters steadily removing all of the waste solids within it
• it is then exposed to chlorine to dispose of any bacteria within it along with any fortifying minerals that are being added

Question 2

What is a “precipitation agent”?

Answer 2

A precipitation agent is added to water so it can bond to the chemicals that are not wanted in the water (eg: metal) and then this precipitate solidifies and can be removed with a filter.

Question 3

Describe “desalination”…

Answer 3

Desalination is the removal of salt from sea water to produce drinkable water.

This is becoming increasingly important for high population countries like India and China, with limited water resources.

It is currently a very high energy intensive process.

CO2 is pumped into the atmosphere during the desalination process due to the burning of fossil fuels to create the required energy.

However, newer and cheaper ways are being looked at which will hopefully cause this problem to recede in the future.

Question 4

Describe a very simple test to see if water is pure…

Answer 4

• boil a sample of the water
• if the whole sample boils away it is pure
• if a substance is left behind then the water is not pure