density Beth

Density
Bethany Faint - 10B

Contents
•
The Discovery of density
•
Formulas and Units of Density
•
Examples of the Density rule
•
Densities of some common substances
•
Floating and Sinking
•
Calculations of density for objects
•
Calculations of density for gas

The discovery of density
• 250 BC - Ancient Greece
•
The King of Syracuse gave his
goldsmith some gold. “Make a
crown”, he said. So the goldsmith
did. But the King was suspicious.
Perhaps the goldsmith had kept
some of the gold. Perhaps he had
mixed in cheaper silver to take its
place. He asked Archimedes to

test the crown.
•
Archimedes knew that the crown
was the correct mass. He knew
that silver was less dense than
gold. So, if the crown contained
any silver it would have more
volume than it should.
• But how could he check the volume
of the crown? Stepping into his
bath one day, Archimedes noticed
the rise in the water level. Here
was the answer to the problem!
Put the crown in the water and
measure the rise in level. Put an
equal mass of pure gold in the
water. See if the rise in level was
the same. “Eureka!” he shouted.
Which is Greek for ‘I have found
it’.
•
Was the crown made of pure gold?
Unfortunately, nobody wrote
down the result. So we shall
never know……

•
Density of the measurement of how close and
how heavy are the particles of matter in an
object.

•
It is measured in kg/m
3
or g/cm
3
or g/mL
•
The Rule for density = Mass/Volume
Formulas & Units of Density

Examples of the Density
Rule
• Q. A stone has a mass of 10
grams. When it is immersed in a
measuring cylinder of water, the
water level rises 5mm. What is
the density of the stone?
• A. Density = Mass/Volume
•
= 10 grams/5 mL
•
= 2 g/mL