Investigating the Differences in Inspired & Expired Air (Cambridge International IGCSE Science)

Investigating the Differences in Inspired & Expired Air

• A simple experimental setup can be used to investigate the differences between inspired and expired air

The limewater test

• When we breathe in, the air is drawn through boiling tube A
• When we breathe out, the air is blown into boiling tube B
• Lime water is clear but becomes cloudy (or milky) when carbon dioxide is bubbled through it
• The lime water in boiling tube A will remain clear, but the limewater in boiling tube B will become cloudy
• This shows us that the percentage of carbon dioxide in exhaled air is higher than in inhaled air

Exam Hint Inspired and expired air means the same as inhaled and exhaled air, you can use either term.