Under the new GCSE specifications in Wales, practical work in Science will be examined. This unit will help students to prepare for the practical examination.
Part ofBiology (Single Science)Practical skills
Try to be more precise in your measuring. Use an instrument with a smaller resolution, and read it to the smallest reading possible.
Ruler A will give a more precise reading and will reduce the uncertainty in your result.
An uncertainty of 1 mm in 25 mm is 4 %.
An uncertainty of 1 cm in 2.5 cm is 40 %. This is ten times bigger.
\({\%{\text{~uncertainty in reading}}}=\frac{\text{instrument resolution}\times 100\%}{\text{reading taken}}\)
The resolution is the smallest division on the instrument.
What is the uncertainty of a resolution of 0.01 ml in 5.52 ml?
(0.01 ÷ 5.52) × 100 % = 0.18 %
What is the uncertainty of a resolution of 0.5 ml in 5.5 ml?
(0.5 ÷ 5.5) × 100 % = 9.1 %