Measurements and uncertainty

Sample questions

Original practice questions written in the style of the exam.

1. Question 14 marks

   In an experiment to find the enthalpy change of solution of ammonium nitrate, a student finds by difference that $1.24\,\text{g}$ of solid was added to water. The balance reads to 2 decimal places ($\pm 0.005\,\text{g}$ per reading). The temperature fell by $6.0\,^\circ\text{C}$, measured with a thermometer with an uncertainty of $\pm 0.5\,^\circ\text{C}$ per reading.

   (a) Calculate the percentage uncertainty in the mass and in the temperature change.

   (b) Identify the larger source of uncertainty and suggest one improvement to reduce it.

   Mark scheme

   • (a) Mass: $2 \times 0.005 = 0.01\,\text{g}$; $0.01 \div 1.24 \times 100 = 0.81\%$ (1)
   • (a) Temperature change: ; (1)