States of matter - AQA SynergyRequired practical - determining density

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 bigger 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 various materials.

Method

Method 1: Regular solids

Method 2: Stone or other irregular shaped object

1. Place the stone on the top pan balance and measure its mass.
2. Fill the displacement can until the water is level with the bottom of the pipe.
3. Place a measuring cylinder under the pipe ready to collect the displaced water.
4. Carefully drop the stone into the can and wait until no more water runs into the cylinder.
5. Measure the volume of the displaced water.
6. Use the measurements to calculate the density of the stone.

Method 3: Water or any liquid

1. Place the measuring cylinder on the top pan balance and measure its mass.
2. Pour 50 cm³ of 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 50 cm³ of water.
4. Use the measurements to calculate the density of the water.

Results

Some example results could be:

Analysis

Using the results from the table above, the densities can be calculated using:

Density = mass ÷ volume

Mass of steel cube = 468 g

Volume of steel cube = 60 cm³

Density = mass ÷ volume

468 ÷ 60 = 7.8 g/cm³ (= 7,800 kg/m³)

Diameter of steel sphere = 2 cm

Mass of steel sphere = 33 g

Density = mass ÷ volume

33 ÷ 4.19 = 7.9 g/cm³ (= 7,900 kg/m³)

For a stone of mass 356 g, the volume of water displaced into the measuring cylinder is 68 cm³.

Density = mass ÷ volume

356 ÷ 68 = 5.2 g/cm³ (= 5,200 kg/m³).

Mass of 50 cm³ of water is found to be 50 g.

Density = mass ÷ volume

50 ÷ 50 = 1 g/cm³ (= 1,000 kg/m³).

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, when 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
  • the displacement can may not have been set up correctly each time and any additional drops of water would cause some to dribble out of the spout before use
• The experiment above shows steel to have two different values for density. One reason may be that some measurements are taken to different numbers of significant figures and this can create rounding errors. It can also mean that the actual value may be between 7.8 g/cm³ and 7.9 g/cm³.

Hazards and control measures