Oxygen in the Atmosphere PCA

Oxygen in the Atmosphere PCA:

Oxygen is essential for humans.

Many substances , including metals, react with the oxygen in the air. Some react quickly and some slowly.

E.g / When Iron rusts it uses up oxygen in the air. Reactions like these can be used to find out the percentage of oxygen in the air.

Experiment:

How much air is used when metal reacts with it?

Hypothesis - 

About one fifth of the volume of air is oxygen

Apparatus and Chemicals - 

• Test Tube
• Beaker (100cm3)
• Ruler
• Iron Wool

Method - 

1 Put about 3 cm depth of iron wool into the test tube and wet it with water. Tip away excess water.

2 Put about 20 cm³ water into the beaker. Invert the test tube and place it in the beaker of water (see diagram). Measure the length of the column of air with the ruler.

3 Leave for at least a week.

4 Measure the new length of the column of air, taking care not to lift the test tube out of the water.

Rusting is an oxidation reaction of iron with oxygen.

iron + oxygen → iron oxide

What you should know:

1.7. Investigate the proportion of oxygen in the atmosphere