Why are Seashells Hard?

Shell Science

Is it possible to soften the hard shell of a snail? Learn what makes shells so tough! Try this experiment to find out.

What You Need

  • Safety goggles (or face mask or swim goggles)
  • Hammer
  • 2 seashells of the same species (e.g., 2 clamshells or 2 snail shells)
  • 2 glass jars
  • White vinegar

What To Do

Caution: You need an adult’s help for this experiment.

  1. Put on your safety goggles and use the hammer to break both shells into several pieces.
  2. Put half of the shell pieces into each of the glass jars.
  3. Cover the shells in one jar with white vinegar. Leave the other shells uncovered.

  4. After three days, remove a few pieces of shell from the vinegar. Put on your safety goggles and use the hammer to break them into even smaller pieces. Do the same with a few pieces of shell from the other jar. Is there any difference between the shells from the two jars?
  5. Wait two more days and repeat Step 4.

How It Works

Shells contain calcium carbonate, which gives them their strength and hardness. Vinegar is an acid. It dissolves the calcium carbonate, making the shells weaker. The longer you soak the shells, the less calcium carbonate they contain and the easier they are to break.

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