DST KSSR

Floating & Sinking Experiment

Diver in a Bottle

Materials you will need: • Paper Clip • Plastic Pen Top with Clip • Plasticine (Modelling Clay) • Empty Plastic Water Bottle with Lid (2L)

Steps:

1.  Make a plasticine (modelling clay) figure 3.5cm (1.25in) long.  Fix the paper-clip to its head and hang it from the pen top.  Fill the bottle with water and drop in the scuba diver.
2.  The pen top should float with its top just above the water level.  Make the figure bigger or smaller if needed.  Then pour in more water and screw the top on tightly.
Why the diver rises and sinks:

When you put the pen top in the water, a bubble of air is trapped inside it.  This trapped air bubble makes the diver less dense than water, so it floats.  When you squeeze the bottle, water squashes the air and takes up more space in the pen top.  Now the diver is denser than water, so it sinks.  When you relax your grip on the bottle, the air in the pen top expands again.  Now the diver is less dense than water, so it comes back up to the surface.