Water Water 1 Water is a molecule made

Water

Water 1. Water is a molecule made up of one oxygen atom joined to two hydrogen atoms.

Test for Water Cobalt chloride paper is used to test for the presence of water… Cobalt chloride paper Water It turns from blue to pink when water is present!

“To see if there are dissolved solids in a sample of water”

Hard and Soft Water. • When water flows over rocks that contain calcium or magnesium ions it becomes hard water. • Hard water is water that does not easily form a lather with soap. Soft water is water that easily forms a lather with soap. •

Experiment – Comparing different samples of water for hardness Procedure – How will you find out which water sample is hardest, and rank them all? How can you make sure the test is fair?

Experiment – Comparing different samples of water for hardness • Diagram Results

Hard water causes many problems: 1. It causes limescale (calcium carbonate) or “fur” to build up in kettles and boilers. 2. It wastes soap.

1. Ion- exchangers – these swap the ions that cause hardness for ions that do not cause hardness.

Distillation of seawater • The water evaporates, then condenses in the liebig condenser. • Water collects in the beaker, salt is left in the flask

Distillation is used to separate a mixture of liquids when the liquids have different boiling points! What happens to the alcohol when it reaches 78 OC? What happens to the water when it reaches 78 OC?

Water treatment

Water Treatment Water supplied to our homes must be attractive looking, odourless and safe to drink. In order to achieve this there a number of steps involved in the treatment of water:

1. Screening – Water is passed through a screen to remove floating things such as plastic bags and wood.

2. Settling – Aluminium sulfate is added to the water. This makes the tiny floating solids stick together and settle on the bottom of the settling tank. 3. Filtration – Water is filtered through filter beds made of gravel and fine sand.

4. Chlorination – Chlorine is added to kill the bacteria in the water. 5. Fluoridation – In Ireland we add fluoride to the water to help prevent tooth decay.

The breakdown of water by electrolysis • When electricity is passed through water, the water is split into hydrogen gas and oxygen gas

Sulfuric acid H 2 SO 4 is added because helps water to conduct electricity and speeds up the reaction There is twice as much hydrogen gas made as oxygen because there is twice as much hydrogen in water as oxygen!