In the second of two articles on developing the processes of enquiry, hypothesis and testing, Alfredo Tifi, Natale Natale and Antonietta Lombardi describe how to build and apply some of the low-cost equipment they have developed.
To recap, science process skills are fundamental to science, allowing everyone to conduct investigations and reach conclusions. We are convinced that there is a serious educational gap in this area, both in bringing these skills into the classroom and in training teachers to do this. To facilitate the introduction of science-inquiry principles in school, we developed a set of lab activities for use in primary and secondary schools. In the first of two articles (Tifi et al., 2006), we discussed the development of these activities and described games involving ‘transformer machines’. Below, we describe contraptions – physical black boxes to inspire exploration, hypothesis and testing.
The principle behind contraptions is similar to that of the operating machines described in our first article, but these are physical black-box machines that have at least two external movable parts that act as input and output. The parts may be coloured threads, rotating knobs or stems, penetrating bars or tilting levers. The two are coupled through an inner mechanism of gears, pulleys and belts, wheels or Technic Lego®. Alternatively, common objects may be used, such as the rollers found in corrector pens.
The students explore the contraptions and do experiments, manipulating one of the external parts (input) and observing causal behaviour (output) on other external parts. The students can only infer the inner mechanism by developing models and comparing the predictions from the models with what happens with the actual machine.
Gear and pulley machines can have two or more wheels of the same or different diameters. They can be coupled using a single thread, or a continuous belt, creating a wide assortment of hidden mechanisms. See below for a construction plan of the tape contraption.
With a simple reel wound with two coloured threads in opposite directions, all hidden inside a card box, you can make a machine in which pulling a red thread causes a white thread on the opposite side to be drawn inside. If the threads are wound in opposite directions on two coaxial bobbins of very different diameters, pulling both threads causes the box itself to move vertically, whereas pulling just one thread causes the other thread to be drawn into the box at a different rate. See below for a construction plan of the thread-lifting contraption.
These investigations were the most popular among grade 4-5 children (ages 10-12): ideas within ‘research groups’ (3-4 pupils) were discussed and the children enthusiastically searched for effective models, using ribbons, wheels, pencil-made axis, and paper stripsw1.
Not only did the students closely observe the machine behaviour and record the factual evidence, as well as conjecturing, improving, debating and defending their models; they also had a strong creative need to make their own prototypes of the models. One group used the principle of the thread machine to build pretty gadgets for their mothers, in which different words of affection were displayed on the same fabric band, depending on the side from which the band was pulled.
The manipulative aspect of these tangible machines encourages representative and kinaesthetic thinking, both of which are crucial for scientific insight and speculation. Furthermore, the children feel comfortable with these investigations, because they are at the same level, tackling a completely new job with classmates of equal abilities. This is in sharp contrast to the low self-esteem that children often have in content-based curricular subjects. It is not uncommon to find children who cope successfully and participate actively in these modelling and creative activities, despite low scores in traditional schoolwork.
When both threads are pulled, the box moves upwards and towards the thread that is rolled around the smaller pulley. Relaxing the pulling force allows the box to drop under gravity. The rates of disappearance and emergence of the two threads are proportional to the diameter of the pulley to which they are fixed.
It is advisable to start playing with a similar machine where the big pulley is absent and the two threads are rolled on the same reel. The children will devise a simpler model; then it will be easier for them to jump to the two-wheel model.
This contraption is very puzzling for children and should be introduced after the simpler gear and pulleys contraptions. The tape contraption can be complicated further by changing one of the two wheels for a bigger one.