Density
1. Which weighs more?
A tonne of gold or a tonne of sawdust?
They both weigh a tonne, gold is just much denser.
2. The density of a substance is the weight of a cm3 block of something. The more it
weighs the denser it is because the particles are packed tighter and therefore
packed more into that little cube.
3. State the density of:
a)
b)
c)
d)
Water = 1 g/cm3
Wood = 0.3 g/cm3
Copper = 8.9 g/cm3
Gold = 18.9 g/cm3
4. To find density you need to the volume of the substance and the weight. You the
divide the mass by the volume.
5. State the mathematical formula for:
a) The volume of a rectangular prism = Length x Breadth x Height
b) Density = Mass ÷ Volume
6. To find the volume of an object that is standard 3D shape (Cube, Rectangle) you
just do Length x Breadth x Height, but if it isn’t standard filling a measuring
cylinder with a set amount of water, dropping the item in and seeing how much
the water rises also works.
7. To predict if a solid will float or sink in a liquid try and compare weight per cm3
and 2 cm3 in your mind to try and find which is denser. If the solid is denser than
the liquid it will sink but if it is lighter is will float.
8. An egg will float in salt water but not in fresh water because salt water is denser
than fresh water and the egg is also denser than fresh water. Since the egg is
denser than fresh water it doesn't float but the egg is slightly less dense than salt
water which allows it to float.
9. A steel boat will float in water because, though steel is denser than water, the
whole boat on average is less dense than water because most of the boat is fill
with oxygen. Also a boat that weighs 1000kg will keep sinking until it has
displaced 1000m3 of water, so as long as the top of the boat is above water by
the time it has displaced its weight it will float.
10. A piece of metal that has a mass of 6g and a volume of 2 cm3 its density would
be 3g/cm3
11. A piece of glass has the measurements of 4x2x3. Its volume would be 24 cm3.
12. A brick has the measurements of 20x8x6. Its volume would be 960 cm3.
13. The volume of the stone would be 20 cm3.
14. The mass of the stone above is 32g, so the density of it would be 1.6 g/cm3