air by mr. bronks composition of air air breathed inair breathed out 79% 21% 0.03%

AirBy

Mr. Bronks

Composition of Air

Oxygen

Nitrogen

Carbondioxide

Air breathed in Air breathed out

79%

21%0.03%

Oxygen in Air

• The part of air that supports combustion or burning

• Used up by breathing so use in hospitals

• Also rusting or corrosion• Rockets carry their own

supply of Oxygen

Rocket Fuel?

Burning thingsWhen something is burned it reacts with oxygen. For example:

Magnesium + oxygen Magnesium oxide

Carbon + oxygen Carbon dioxide

Sulphur + oxygen Sulphur dioxide

The Fire Triangle

Fire

Fuel

Oxy

gen

Heat

Percentage of Oxygen

When we cover the candle the oxygen is used up – the water rises to fill the gap

We measure the rise and find it’s around 21%

Candle

Water

Gas Jar

Testing for carbon dioxide

Air

Limewater turns milky/cloudy

Limewater

Proves Carbon Dioxide in Air

Testing for Water Vapour in Air

Drops on the test tube

Ice and Salt

Cobalt Chloride Paper turns pink in the presence of water

CO2

Catalyst• A substance that speeds up a

chemical reaction but is not used up in the reaction. Here platinum is used as a catalyst in this catalytic converter.

CO2

CO

CO2

Catalyst• A substance that speeds up a

chemical reaction but is not used up in the reaction. Here platinum is used as a catalyst in this catalytic converter.

CO2

COCO2

Oxygen

• Catalyst speeds up reaction but is not used up – Manganese Dioxide

• Oxygen does not dissolve in the water

Test for Oxygen

• Relights a glowing splint

Oxygen

Test for Oxygen

• Relights a glowing splint

Burning Magnesium in Oxygen• Burns much brighter• In fact goes crazy-nuts-bright-and-

scary

Oxygen

• Very Bright Flame

Burning Magnesium in Oxygen

• White Powder remains- Magnesium Oxide

Burning Magnesium in Oxygen

• Add water

2MgO +H2O2Mg(OH)

Water

2MgO +H2O2Mg(OH)

Water

Red Litmus turns Blue colour proves liquid is a BASE

• Very Bright Flame• White Powder remains-

Magnesium Oxide

Burning Magnesium in Oxygen

Add water and Red Litmus paper turns Blue colour proves liquid is a BASE

Rusting also needs Oxygen

Just like the candle the steel rusts and oxygen is used up. The space is filled with water

Steel wool

Water

Gas Jar

2 weeks later

Rusted

Preventing Rusting

Metals needs water and oxygen to rust

Preventing Rusting

• Plating• Painting• Greasing• Dry• Galvanising

Summary

H/W

• P233• Q 1,2,3,4,5.