Density (formula: D = mass/volume)

Key Formulas:

Mass = Density x Volume

Volume = Mass/Density

Density tells you how much mass is packed into a certain volume.

Imagine two cubes that are exactly the same size:

  • One is made of wood.

  • One is made of iron.

The iron cube is heavier because more mass is packed into the same amount of space,There fore iron is denser than wood.


If two objects take up the same amount of space the one with the more mass has the higher density.


Key measurements;

Mass = g or kg

Volume = cm³ or m³ ml L

Density= g/cm³ or kg/m³

Liquid volume can also be measured in mL, Ex: 1 cm³ = 1mL or 1g/cm³ = 1000kg/m³

  • To convert g to kg divide by 1000

  • To convert Kg to g multiply by 1000

  • Large to small:l ( x ) , Small to large ( divide/)


Rectangular shaped objects

Formula : V = L x W x H


Irregular shaped objects:

  • Irregular-shaped objects cannot be easily calculated. For example to calculate a rock, using this exact formula isnt right. Instead, you can use the water displacement method.


1: pour water into a measuring cylinder

2: record initial water level

3: carefully submerge the object completely

4: record final water level then subtract the initial level from the final level.

Object volume = Final reading - Initial reading

Ex: V = 65ml - 40ml = 25cm³, Since 1 mL = 1cm³.


Floating and Sinking

    An object floats or sinks depending on its density compared to the liquid.

  • Less dense than the liquid : FLOATS

  • More dense than the liquid : SINKS

  • Same density as the liquid: can stay suspended (the object stays in the middle of the liquid).


An object has a mass of 120g and a volume of 15 cm³. find the density ..= 8g/cm³


Find the mass: A liquid has a density of 2g/cm³ and a volume of 15 cm³. 30g


Find the volume; an object has a mass of 80g and a density of 4 g/cm³ = 20cm³


A block is 5cm long, 3cm wide and 2 cm high. = 30cm³





Water rises from 25mL to 42mL when a rock is submerged what is its volume? write your answer in cm³.


An object has mass 60g and density 3g/cm³.What is its volume? 20cm ³


Why is water displacement useful for a rock?

  • it measures the rocks mass

  • it gives the volume of an irregular object yes

  • it measures the rocks temp.


A student reads a measuring cylinder from above eye level.What might happen?

  • The mass changes

  • A parallax error affects the reading

  • The object’s density becomes zero