Mass in each volume
Density = Mass ÷ Volume.
Wood and iron
A wooden stick and an iron rod are of the same size. The iron rod feels much heavier.
What property tells how heavy a substance is for its size?
What this lesson covers
The idea
Density is the mass present in a unit volume of a substance: Density = Mass / Volume; it describes how heavy a substance is for its size.
Wood and iron
A wooden stick and an iron rod are of the same size. The iron rod feels much heavier.
What property tells how heavy a substance is for its size?
- Density
- Colour
- Length
Find the density
Pick a mass and a volume. Make a density of 2 g/cm³.
Mass per unit volume
Density is the mass present in a unit volume of a substance. It tells how heavy a substance is for its size.
Density = Mass ÷ Volume. It is the mass in each unit of volume.
- Mass | Volume | Density
- 20 g | 10 cm³ | 2 g/cm³
- 40 g | 10 cm³ | 4 g/cm³
- 40 g | 20 cm³ | 2 g/cm³
Notes
Density = Mass ÷ Volume. It tells how heavy a substance is for its size.
Check yourself
Density is the mass present in …
A block has a mass of 40 g and a volume of 20 cm³. What is its density in g/cm³?
Answer: 2 g/cm³
40 g ÷ 20 cm³ = 2 g/cm³.
A block of aluminium has a mass of 27 g and a volume of 10 cm³. What is its density in g/cm³?
Answer: 2.7 g/cm³
27 g ÷ 10 cm³ = 2.7 g/cm³.
An iron rod and a wooden stick are the same size, but the iron rod is heavier. Iron has the greater …
- a unit length of a substance. Density is mass per unit volume.
- a unit volume of a substance — correct. Yes!
- a unit time. Density is mass per unit volume.
- length. They are the same size. The iron has a greater density.
- volume. They are the same size. The iron has a greater density.
- density — correct. Yes!