Science corner

12th March 2004 at 00:00
Easter activity: Sophie Duncan uses chemistry to make an eggshell ornament

Easter and eggs go together - and this week's activity investigates a way to decorate your classroom with eggs and the help of some chemistry.

If you place an egg in vinegar, the calcium carbonate in the shell will react with the acidic vinegar. Small bubbles of carbon dioxide can be observed on the shell, and after a couple of days the shell will have vanished, leaving the contents of the egg exposed. The white and yolk are held together in a semi-transparent skin of tissue that is not dissolved by the vinegar.

You can use this experiment to make eggshell decorations. First take your egg and consider how you would like it to look. Colour the shell with patterns using wax crayons, leaving areas where there is no colour. The unwaxed parts will react with the acid, so design it carefully to ensure the decoration will still be egg-shaped once those parts of the shell are gone.

Soak the decorated eggs in a container of vinegar for 24 hours. The unwaxed areas of shell will disintegrate. The coloured areas are protected by the wax, so remain intact.

The egg contents should be removed. Carefully puncture the skin around the egg and pour the contents into a bowl. Wash the shell carefully to remove all yolk and white, making sure you wash your hands afterwards. Tie a ribbon on to your egg and you have a lovely, light Easter decoration.

Eggs are very strong - you can show just how strong they are by trying this experiment. Break two eggs in half and remove the contents. Wash out the shell. Place the four halves on a flat surface, curved end up. Place a thin tray on top of them. Carefully add small weights to the tray - try books, or bean bags. See how much weight the eggs can support before they crack.

Sophie Duncan is project manager for science at the BBC www.bbc.co.ukscience

Rockets: in February 13 Science Corner we said Newton's "second" law of motion where we should have said "third". The explanation of the action involved was, of course, simplified for key stage 2 classes.

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