15 - Air and Water

Question 1

Describe the 3 ways to test for water

Answer 1

1. Blue Cobalt II Chloride Paper turns blue to pink
2. Anhydrous Copper II Sulfate powder turns from white to blue crystals
3. Testing melting and boiling points. The melting point is 0 degrees Celsius and the boiling point is 100 degrees Celsius.

Question 2

Where does water come from?

Answer 2

Water that is pumped into our homes is from groundwater which is a rock underground that contains water. Water also may come from rivers

Question 3

How is water purified?

Answer 3

1. Water is pumped into screens that remove solid floating debris
2. A coagulant is added to make particles stick together such as aluminum sulfate.
3. Water is brought to the floatation tanks where the coagulated particles float to the top and are skimmed off.
4. Water is filtered through coarse sand to remove larger insoluble debris.
5. It then goes through further filters such as more sand or charcoal which removes bad tastes and smells.
6. Chlorine is added to kill bacteria and other microbes
7. Fluoride is added to fight tooth decay

Question 4

State the uses of water

Answer 4

At Home:
1. Drinking
2. Cooking
3. Washing

In Industry:
1. Washing
2. Dissolve
3. Used for steam

Question 5

State the composition of clean air

Answer 5

79% nitrogen
20% oxygen
Remainder: Noble Gases, carbon dioxide, water vapor

Question 6

State all the pollutants in the air, their source, and the problems that they cause

Answer 6

1. CO = Incomplete combustion = Reacts with hemoglobin causing it to be unable to carry oxygen
2. Sulphur Dioxide = From the combustion of fossil fuels that contain sulfur = Irritation to the eyes, throat, and respiratory problems. Causes acid rain.
3. Nitrogen Oxides = Car exhausts = Forms acid rain and respiratory problems
4. Lead = From burning petrol as lead for better performance = Damage to brain and nerve cells in young children

Question 7

State the importance of catalytic converters in car exhausts

Answer 7

Insufficient amounts of oxygen lead to incomplete combustion of carbon in fuel which produces pollutants: oxides of nitrogen and carbon monoxide.

This is why the catalytic converter catalyzes the reduction of NO2 into N2 and oxidation of CO into CO2 which is less harmful to the air.

Question 8

Describe how fractional distillation of air works

Answer 8

1. Air is filtered to remove dust
2. Water and carbon dioxide are removed.
   
   • Water vapor (air is cooled causing it to condense
   • Absorbent beads trap carbon dioxide
3. The air is compressed causing it to heat up but is cooled by recycling
4. Cold compressed air passes through a jet which makes it very cold.
5. Steps 3 and 4 are repeated until the air turns liquid except for neon and helium which are removed using charcoal.
6. Liquid air is pumped into a fractioning column which is slowly warmed up. The different gases boil off one by one and are collected in tanks. The gas with the lowest melting point are collected first because they evaporate first.

Question 9

What is required for rusting?

Answer 9

Oxygen and Water

Question 9

How to prevent iron from rusting?

Answer 9

1. Coating with plastic, paint, and grease
2. Electroplating with tin or chromium
3. Galvanizing with molten zinc
4. Sacrificial Protection: Attaching a piece of metal more reactive than iron