Science corner

2nd December 2005 at 00:00
Sophie Duncan makes flowers that bloom in water.

Take a circle of paper about six centimetres in diameter. Draw lines through the centre to divide the circle into six equal segments. Each line needs to be marked halfway between the centre and the outside of the circle.

Cut along each line, stopping at the mark. These are the petals of the flower. Cut around the edge of each segment to make a petal shape.

Fold the petals into the centre, making sure that the folds are pressed down firmly. Place the flower in a bowl of water. The petals should unfold.

Water is drawn into the paper through capillary action. The folds put the paper fibres under tension. As the paper absorbs water, the fibres swell up and the petals unfold.

While this experiment demonstrates a scientific principle, the fun doesn't need to end here.

Different types of paper absorb water at different rates. Newspaper and tissue paper absorb water quickly and these flowers will bloom almost immediately, but other papers respond less quickly.

Why not encourage your students to try and define a fair test to work out how quickly different papers absorb water. What are the characteristics of papers that absorb water quickly and slowly?

You could try testing strips of paper dipped into water and measuring the time it takes for the water to travel up the paper. Adding some food colouring to the water might make it easier to measure the time.

Alternatively you could drop equal amounts of water on to a sheet of paper, and watch how far the drop expands over time.

Once you have ranked the papers, you can make a set of flowers that bloom over time. You can also try making flowers of different shapes and sizes for an even more interesting display.

With Christmas coming up you could use snowflakes or star shapes instead.

Other folded shapes also work as well.

Try a concertina of paper. Place it in the water and watch as the paper flattens out.

Sophie Duncan is project manager for science at the BBC

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