Carbon cycle: exchanging carbon dioxide between the atmosphere and
ocean (for pupils)
Carbon dioxide dissolves in the ocean. There is an
exchange of carbon dioxide between the atmosphere and the oceanís surface.
Universal indicator goes yellow in the presence of
Carbon dioxide dissolved in water (known as being in
solution) is acidic.
What you need
Universal Indicator solution
Tap water (fresh water)
A copy of the carbon cycle diagram (below)
Wear eye protection. Blow gently through the straws;
do not suck up water. Dispose of the straws at the end of the
What to do
- Pour 100 cm3 of sea water into one
beaker and 100 cm3 of fresh water into the other beaker.
- Put several drops of universal indicator into
- Using the straw, blow gently and consistently into
the water, first for the sea water, then the fresh water. For each, time
how long it takes the indicator to become yellow. Record the results.
What did it mean when the indicator was yellow?
Which beaker turned yellow quickest?
Which water absorbs more carbon dioxide before becoming acidic?
Highlight this part of the carbon cycle on your diagram.
Overall questions on the carbon cycle
Carbon is in the cycle in solid, liquid and gas forms. Which products
show each of these forms (one example of each)?
Which processes happen quickly (give examples)? Which ones happen very
slowly (give examples)?
Which processes are going on outside the window today?
Which processes do you take part in?
Which processes did dinosaurs take part in?
Coal and natural gas form from ancient plants. What processes affected
these plants that probably wonít affect the plants you see outside the