3B Scientific Density Paradox Set User Manual

3B SCIENTIFIC® PHYSICS

Density Paradox Set U45056

Instructions

05/11 ALF

1. Safety instruction

This experiment uses hot water. Risk of scalding!

• Be careful using hot water.

2. Description

The density paradox set consists of two identical
plastic cylinders with hooks, which have a density
close to that of water.

3. Technical data

Length: 60 mm approx.

Diameter: 20 mm approx.

Weight: 8 g each approx.

4. Operation

The following equipment is also required to carry out
this experiment:
2 Beakers from U14210 (set of 10 beakers)
String

• Tie some string to both cylinders.

• Fill one beaker with hot water and the other with

very cold water.

• Dangle both cylinders in the beaker with the hot

water.

The cylinders initially sink, but after a short time they
rise back to the surface.

• Take the cylinders out of the hot water and

dangle them in the beaker with the cold water.

The cylinders initially float but shortly afterwards they
sink to the bottom.

Explanation:

Unlike liquids, the density of most solid bodies
undergoes little change. The material from which the
two plastic cylinders are made is an exception to this
which leads to their apparently paradoxical
behaviour. The cylinders sink in hot water because the
water is less dense than they are. Heat causes the
cylinders to expand so that their density decreases to
less than that of the hot water. This is why they rise to
the surface and float after a while. In cold water, the
cooling causes the density to increase to more than
that of the cold water.

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Subject to technical amendments

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