To demonstrate why our trachea needs cartlige to keep it open
- take 2 sheets of paper (or balloons)
- hold them a few centimeters apart
- blow through the gap (or use a hairdryer)
- What do you expect
- observe the gap between the sheets
When air passes through a narrow place the pressure decreases which means that the tube will normally collapse.
Rings of cartilage are needed to keep the wind pipe open.
The products of respiration
To test for Carbon Dioxide
Limewater, Test-Tubes (or conical flasks), Bungs (corks), Glass tubes & drinking straws,
- Half fill test-tube with (clear) Limewater
- Put in 2 glasstube bung
- Decide if you will Inhale or exhale, your partner should do the opposite.
- By exhaling or inhaling bubble gas through the limewater for a set number of breaths
- Compare with your partner the colour of the limewater
The tube through which we exhaled was Cloudy / Milky
The tube through which we inhaled was left clear
Lime water goes Milky when in contact with Carbon Dioxide CO2
Therefore exhaled breath has MORE carbon Dioxide than Inhaled air
To test for Water Vapour from your breath
Cold Tile, Anhydrous Copper Sulphate Powder (white)
- Remove tiles from fridge after spending time there overnight
- Exhale / Breath on cold tile
- Sprinkle copper sulphate powder on the tile
- Observe any changes
The Anhydrous Copper Sulphate Powder went blue in colour
Copper Sulphate Powder is blue when in contact with water
The water vapour from our breath condensed on the cold tile.
We produce water vapour when we respire
Cobalt Chloride can also be used to test for water vapour, however these test papers are hard to use when they get old. Also these papers are banned in Irish Schools
Blue Cobalt Chloride Paper goes Pink in the presence of water