Specified practical

Determination of the density of liquids and solids

There are different ways to investigate density. In this required practical activity, it is important to:

  • record the mass accurately
  • measure and observe the mass and the volume of the different objects
  • use appropriate apparatus and methods to measure volume and mass and use that to investigate density

Aim of the experiment

To measure the density of liquids and solids.

Method

Method 1: A regular shaped object

  1. Use a ruler to measure the length (l), width (w) and height (h) of the object.
  2. Place the object on the top pan balance and measure its mass.
  3. Calculate the volume of the cube using ( l \times w \times h).
  4. Use the measurements to calculate the density of the object.

Method 2: An irregular shaped object

  1. Place the object on the top pan balance and measure its mass.
  2. Fill a measuring cylinder so that there is enough water to cover the object when it is placed inside the cylinder. Take the reading of the volume.
  3. Carefully lower the object into the cylinder.
  4. Take the new reading of the volume. Subtract the original reading to obtain the volume of the object.
  5. Use the measurements to calculate the density of the stone.

Method 3: A liquid

  1. Place the measuring cylinder on the top pan balance and measure its mass.
  2. Pour eg 30 cm3 of liquid (eg water) into the measuring cylinder and measure its new mass.
  3. Subtract the mass in step 1 from the mass in step 2. This is the mass of 30 cm3 of water.
  4. Use the measurements to calculate the density of the water.

Results

Some example results could be:

Object Mass (g)Volume (cm³)Density (g/cm³)
Steel block46860
Stone35668
Water3030

Analysis

Using those results – the densities can be calculated using:

Density = mass ÷ volume

Mass of steel block = 468 g

Volume of steel block = 60 cm3

Density = mass ÷ volume = 468 ÷ 60 = 7.8 g/cm3

For a stone of mass 356 g, the volume of water in the measuring cylinder rose by 68 cm3.

Density = mass ÷ volume = 356 ÷ 68 = 5.2 g/cm3

Mass of 30 cm3 of water is found to be 30 g.

Density = mass ÷ volume = 30 ÷ 30 = 1 g/cm3

Evaluation

  • Density can be measured for regular solids, irregular solids and liquids.
  • Densities calculated from measurements are subject to experimental error. This could be because:
    • the top pan balances used by different people may not be identically calibrated
    • the resolution of the measuring cylinders may be different, causing different values for the volume to be recorded

Risk assessment

HazardRiskControl measures
There are no significant risks associated with this procedure