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Inhaled and Exhaled Air

This worksheet will explain the main differences between inhaled and exhaled air.

'Inhaled and Exhaled Air' worksheet

Key stage:  KS 3

Curriculum topic:  Biology: Structure and Function of Living Organisms

Curriculum subtopic:  Gas Exchange Systems (Breathing)

Difficulty level:  

down

Worksheet Overview

QUESTION 1 of 10

Breathing

 

Everyone knows that we breathe in oxygen and breathe out carbon dioxide. But that's not technically true. The truth is we breathe in air and breathe out air... so what's the difference?

 

Inhaled Air

So, we need oxygen to live, but do you know how much of the air is made up of oxygen? 80%? 75%? ....it actually only makes up ~21% of the air.  

So what else is in there?

The air that is all around us is made up of mostly nitrogen, ~78% nitrogen in fact. So what about the other 1%? ...The other 1% is made up of ~0.04% carbon dioxide, some water vapour and other gases such as argon, helium and neon.  

 

 

Exhaled Air

The reason we breathe is to get oxygen into our bodies to allow for respiration, so you would think that the air we breathe out would have a lot less oxygen right? Well, there is less oxygen in exhaled air but probably a bit more than you would expect. Exhaled air actually contains ~16% oxygen which means we only use ~5% of the oxygen available!

The percentage of nitrogen stays at ~78% (as we do not have any use for nitrogen) but the main different is the increase in carbon dioxide. The carbon dioxide in exhaled air is ~4% and the percentage of water vapour is also higher than in inhaled air.  

 

 

 

Experiment Time

There is a very simple experiment that we can do to prove that exhaled air contains more carbon dioxide than inhaled air.

Carbon dioxide will turn colourless limewater milky/cloudy.  

 

 

The CO2 percentage in inhaled air is so small that is have not effect on the limewater, however bubble some exhaled air through it and it will turn milky/cloudy. 

Which gas makes up ~78% of the air around us?

oxygen

carbon dioxide

nitrogen

water vapour

How much of the air we breathe in is oxygen?

~16%

~21%

~50%

~78%

How much oxygen would you find in exhaled air?

~0.04%

~16%

~21%

~78%

Other than carbon dioxide, which gas would you find more of in exhaled air?

carbon monoxide

oxygen

nitrogen

water vapour

Fill in the correct percentages of gases found in inhaled air.

(We ought to include the ~ symbol (which means approximately), but just write the numbers in the table below).

 Percentage (%)
Nitrogen
Oxygen
Carbon Dioxide

What is the chemical test for carbon dioxide?

Relights a glowing splint

Turns lime water milky/cloudy

Burns with a squeaky pop

Turns universal indicator purple

Why does lime water not change when inhaled air is bubbled through it?

The percentage of carbon dioxide is too high

The percentage of carbon dioxide is too low

The percentage of oxygen is too high

The percentage of oxygen is too low

Fill in the correct percentages of gases found in exhaled air.

(We ought to include the ~ symbol (which means approximately), but in this case just write the numbers in the table below).

 Percentage (%)
Nitrogen
Oxygen
Carbon Dioxide
  • Question 1

Which gas makes up ~78% of the air around us?

CORRECT ANSWER
nitrogen
  • Question 2

How much of the air we breathe in is oxygen?

CORRECT ANSWER
~21%
EDDIE SAYS
  • Question 3

How much oxygen would you find in exhaled air?

CORRECT ANSWER
~16%
EDDIE SAYS
  • Question 4

Other than carbon dioxide, which gas would you find more of in exhaled air?

CORRECT ANSWER
nitrogen
  • Question 5

Fill in the correct percentages of gases found in inhaled air.

(We ought to include the ~ symbol (which means approximately), but just write the numbers in the table below).

CORRECT ANSWER
 Percentage (%)
Nitrogen
Oxygen
Carbon Dioxide
  • Question 6

What is the chemical test for carbon dioxide?

CORRECT ANSWER
Turns lime water milky/cloudy
EDDIE SAYS
Colourless lime water will turn milky or cloudy in the presence of carbon dioxide.
  • Question 7

Why does lime water not change when inhaled air is bubbled through it?

CORRECT ANSWER
The percentage of carbon dioxide is too low
EDDIE SAYS
There is no change in the lime water when it is in the presence of inhaled air because there is not enough carbon dioxide in inhaled air (only 0.04%) to have any effect on the lime water.
  • Question 8

Fill in the correct percentages of gases found in exhaled air.

(We ought to include the ~ symbol (which means approximately), but in this case just write the numbers in the table below).

CORRECT ANSWER
 Percentage (%)
Nitrogen
Oxygen
Carbon Dioxide
---- OR ----

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