Quick answer: Density is mass per unit volume, ρ = m ÷ V. This Physics 9-10 lab on density and pressure gives the aim, the equipment, the safety points, a step-by-step method, sample results and 7 analysis questions; the answers are on a separate page and the lab sheet is a free printable PDF.
How can you find the density of a block, a stone or a liquid with a ruler, a balance and a measuring cylinder? In this lab you measure mass and volume for four samples, calculate their densities and decide which would float. You also compare the reliability of different volume measurements.
Level: Physics grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: GCSE P3, IGCSE 1.8
Aim
To determine the density of a regular solid, two irregular solids and a liquid, and to decide which float in water.
Equipment
- Digital balance (0.1 g)
- 100 cm³ measuring cylinder, water, thread
- Ruler, wooden cube, steel bolt, small stone
- Cooking oil, small beaker
Safety
Wipe up any spilled water or oil at once because the floor becomes slippery. Lower solids gently into the cylinder so that glass does not break. Do not taste the oil.
Method
- Measure the mass of the wooden cube on the balance. Measure its edge with the ruler and calculate the volume.
- Measure the mass of the bolt. Fill the measuring cylinder to 40.0 cm³, tie the bolt to the thread, lower it in slowly and read the new level. The volume is the rise.
- Repeat step 2 for the stone, using a level of 40.0 cm³ again.
- For the oil, measure the mass of the empty beaker, pour exactly 50.0 cm³ into the beaker using the cylinder, then measure the mass of the beaker with oil. Subtract to find the mass of oil.
- Calculate the density of each sample using ρ = m ÷ V.
Results
Sample results (readings at the bottom of the meniscus):
| Sample | Mass m (g) | Volume V (cm³) | Density ρ (g/cm³) |
|---|---|---|---|
| Wooden cube (4.00 cm edge) | 38.4 | 64.0 | 0.60 |
| Steel bolt | 31.2 | 4.0 | 7.80 |
| Stone | 43.5 | 15.0 | 2.90 |
| Cooking oil | 46.0 | 50.0 | 0.92 |
The stone raised the water level from 40.0 cm³ to 55.0 cm³, and the bolt from 40.0 cm³ to 44.0 cm³.
Analysis questions
Question 1 Wooden cube
Show that the volume of the cube is 64.0 cm³ and calculate its density.Question 2 Convert the stone
Calculate the density of the stone in kg/m³.Question 3 Identify the bolt
Compare the density of the bolt with the table of the lesson and identify the metal. Give the density in kg/m³.Question 4 Float or sink
State whether each of the four samples floats or sinks in water (1.00 g/cm³), giving a reason.Question 5 Fraction under water
The wooden cube floats. Use its density to calculate the fraction of its volume below the water surface.Question 6 Reading uncertainty
Each level reading in the cylinder has an uncertainty of ±0.5 cm³. Calculate the percentage uncertainty in the volume of the bolt and of the stone, and state which density is more reliable.Question 7 Improve the lab
Suggest two ways of improving the accuracy of the densities.
