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This activity demonstrates the ability of an acidic substance (in this case, vinegar) to ‘dissolve’ coral reefs and shells which protect ocean life.

Although corals and shells are not dissolving as fast as demonstrated in this experiment, it is possible to reach these levels in the future.

What you’ll need

  • Clear cup or container
  • ½ cup of vinegar
  • A piece of chalk or sea shells

Activity steps

  • Carefully half fill a clear cup or container with clear vinegar.
  • Add a piece of chalk to the container. Some chalk is made with a protective cover to stop chalk rubbing off on hands. It may help to break a piece of chalk into smaller pieces to better see effects of the vinegar.
  • Observe what is happening. Older children and adults can try to guess the chemical reaction that is taking place.

Safety guidance

  • Check that there are no allergy issues to chalk or vinegar.

More ideas
You can also try this activity using sea shells instead of chalk. If you do not live near the sea, these could be collected from a local restaurant that serves sea food. Shells with rough or ridged surfaces will react more quickly than those with smooth surfaces.

Find out more
You may be able to observe bubbles on the surface of the chalk. Vinegar contains acetic acid. The acid reacts with the calcium carbonate (ie the chalk) to form calcium ions, water and carbon dioxide.

2H(acid) + CaCO(chalk) -> Ca2+ (calcium ions) + H2O (water) + CO(carbon dioxide)

Ocean acidification

This process of atmospheric carbon dioxide dissolving into the ocean, and turning the waters more acidic is shown below.

Subject Update Learn More Ocean Acidification Process Figure 1
Ocean acidification diagram

At a larger scale, this experiment shows how powerful the impacts of ocean acidification can be. One of the problems associated with ocean acidification is that it affects the balance of carbonate ions in the oceans. These ions are the chemical building blocks used by a number of organisms to create shells and structures, including corals. Less carbonate ions makes life more difficult for creatures to make their carbonate structures. As more energy is spent on building structures, less energy is available for other processes such as reproduction and growth.

Gallery Coral Life Mantis ShrimpXL Catlin Seaview Survey
This mantis shrimp has an exoskeleton that contains calcium carbonate, which could be damaged if the ocean becomes more acidic.

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