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Ocean CO2 Absorption – Worksheet


Does warm or cold water absorb CO2  better?

If the oceans are absorbing large quantities of carbon, and if we know the oceans are warming due to global warming, what is the effect of warmer oceans on CO2 absorption? Let´s check with this experiment that shows how much CO2 will dissolve in the water and how much will be in its gaseous form above the water.cr





2 x 500 ml measuring cylinders

Effervescent fizz tablets (e.g. Alka Seltzer)

2 x Petri dishes that fit over the cylinders

Ice (optional)

Bowl or container of at least 5 litres


Stand and clamp to hold cylinders


Water heater


Funnel (optional)


  1. Fill the basin half-full with cold  (or iced) water. Place the stand beside the basin.
  2. Fill the graduated cylinder to the brim with cold water and cover the top of the cylinder with the petri dish. Turn it upside down in the basin, making sure that no water spills out of the cylinder (so no air bubble forms). Remove the Petri dish when the cylinder is already underwater.
  3. Secure the graduated cylinder with the clamp to the stand and place the funnel in the mouth of the cylinder.
  4. Place an effervescent tablet carefully under the funnel. (Be sure your hands are dry so as to not set off the reaction prematurely).
  5. Observe the air space that develops at the top of the upside-down cylinder. Record the volume of the air space formed.
  6. Repeat the same procedure with warm water and record your results in the table. What happens to the air space when warm water is used? Is more or less air released than with cold water?
  7. Repeat the same experiment two or three times more with both cold and warm water.

Results table


Experiment number

WARM water (volume of air/ml)

Experiment number

COLD water (volume of air/ml)

















AVERAGE volume


AVERAGE volume



Question: Does more CO2 escape from warm or cold water?


If more has escaped from the liquid, the water cannot absorb as much CO2.

Extension Question: With global warming and warmer oceans, will the oceans be able to absorb more or less CO2 than before?

What is the perfect pH of the oceans? Is it different depending on which ocean and whether it is in the deep ocean or the shallower coastal areas?

Start exploring

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