Ocean Acidification and CO2 Absorption

In this experiment students initiate a reaction that produces CO2 in an enclosed water-air environment. The CO2 formed will be absorbed into the water, making it more acidic and changing the colour of the indicator. The experiment can be carried out in pairs and takes about 15 minutes. An additional experiment to test the solubility of CO2 in warm and cold water can be carried out afterwards, explaining how global warming can affect marine CO2 absorption.

©The Royal Meteorological Society. All rights reserved.

~ 1 hour


Download the resource below.

What you need

  • Bicarbonate of soda (baking soda)
  • White vinegar
  • Bromothymol blue Indicator (diluted with water: 8 ml bromothymol blue (0.04% aqueous) to 1 litre of water)
  • 2 x 500 ml Beakers
  • Small plastic or paper cup (100 ml)
  • Masking tape
  • 2 x Petri dishes or lid for large beakers
  • Teaspoon or 5 ml measuring cylinder
  • Two sheets of white paper
  • Safety glasses and lab coat


  • Indoor

Curriculum links

  • Chemistry
  • Physics
  • Geography