Helping you explore how science works with post-16 students

Lesson D: Chemical data

Key facts

  • Relevance: AS/A chemistry

  • Time: 60 minutes

Download resources


Many of the investigations conducted by professional chemists involve making measurements. However, there is a degree of uncertainty about the data sets that result from these measurements.

In many investigations in chemistry (and other fields) theoretical models are used to decide which measurements are made and how the resulting data are analysed. 

In considering the implications of such investigations, chemists need to recognise the potential uncertainty that results from the use of models and analogies.

The focus of this teaching is to enable students to recognise a range of different sources of uncertainty in investigations, and to appreciate how this uncertainty can be handled.


The lesson aims to teach students:

  • the different reasons why scientific measurements always include a degree of uncertainty; 
  • the techniques that scientists use to deal with experimental error, particularly the use of error bars. 


This lesson consists of four activities.

Activity D1

Students are presented with cards that describe pieces of scientific research and draw attention to uncertainty in the research. Students are asked to identify the sources of that uncertainty. The teacher takes feedback from the group and classifies the uncertainty in terms of human error, random error, systematic error or uncertainty arising from assumptions and models used.

Activity D2

With the aid of notes and OHTs the teacher gives a short presentation explaining some of the ways scientists deal with uncertainty. The presentation includes the meaning of error bars, the use of lines of best fit and the distinction between accuracy and precision are described. Students are then asked to use these ideas in the context of published data tables.

Activities D3 and D4

In these activities the issues already raised are reinforced through consideration of a published piece of chemistry research and some A-level chemistry work.