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Physics practical

Density by displacement

Weigh five pebbles, find their volumes by displacement, and use the gradient of mass against volume to identify the rock.

What you will do

  1. 01Weigh each dry pebble on the top-pan balance.
  2. 02Part-fill the measuring cylinder with water and read the level at the bottom of the meniscus.
  3. 03Lower the pebble gently into the water and read the new level. The rise is its volume.
  4. 04Take the pebble out, blot it dry, and read the starting level again before the next one.
  5. 05Plot mass against volume, draw the best straight line and find its gradient: the density.
  6. 06Compare the density with the table to identify the rock.