2. Organising a ‘circus’ of experiments
Organising a laboratory parade (or circus of experiments) is a good way to enable students to perform their own experiments when you only have one set of apparatus. By devising a set of activities which are related, students move from station to station and gradually build up their understanding. Again, the students will be working in groups. You will need to decide how to organise the groups. You are also encouraged to think about ways of challenging the students who have a good understanding of the work.
By getting each group to measure the same objects and record their results on the board, you will be able to explain the concepts of ‘accuracy’ and ‘precision’. There is also an opportunity to calculate averages. Case study 2 describes a situation in which the teacher does not have very much equipment. Activity 2 shows what you can do with more equipment and Resource 4 gives you some specific ideas.
Case study 2: Making measurements
Mrs Otieno has limited access to measuring instruments and teaches in a mixed school. She had noticed that whenever they worked together the boys tended to do the work while the girls watched. She organised three stations for measuring the diameter of a pipe, the mass of small stones the students had brought from a nearby river and the volume of the same stones. With work stations for each measurement, she divided the class into groups of boys and girls. At the same time she had drawn a table on the board with a column for readings of volume, diameter and mass. She had three beam balances, three eureka cans, three measuring cylinders and three vernier calipers. Each group was asked to measure and record the value on the appropriate column on the board, within 5 minutes, and then move to the next station. In a previous lesson she had demonstrated how the vernier calipers, beam balance and measuring cylinder worked. The students enjoyed handling the apparatus, especially the girls who filled in their results before the boys. She also noted with a lot of pleasure how creative the students were in using the eureka can. There were variations in the readings. Mrs Otieno used this to help her students understand the idea of ‘uncertainty’ and the importance of using averages. She asked them to calculate the average for each of the three readings.
Activity 2: Thinking about ‘uncertainity’
Set up some different activity stations around the room. There are some suggestions in Resource 4 , but you may need to use different ones, depending on the equipment that you have available. Divide your class into groups and give them 4 or 5 minutes at each station. (Use a stop watch to time it.) While they are working, make a table on the board with a column for each station and ask one person from each group to write their measurements in the correct column. Emphasise that they should write their answer, even if it is different from the others. At the end gather them round the front and ask them to think about why some of the answers might be different. You could get them to calculate some averages and explain the difference between precision and accuracy. For the activities that used imprecise equipment (e.g. kitchen measuring jug) you could ask them to name a more accurate piece of equipment for doing the same job.