This is a blog on practical work in science and technology. Children can’t learn science and technology simply from books; they have to experience what the physical world really does.
Practical work in science and technology can be the vital connection between the natural world out there and the world of connected ideas inside a child’s mind. But we have to make that connection happen. Work with their hands is essential but children have to put the experience into their own words — it’s language that captures the concepts that come from practical work. Language we see in group talk, in talk to the class, in drawings to help the words, and in structured writing that we ask them to do.
Unless we hear their words (and see their pictures) we never really know what is in their minds. When they give us the correct answers in a test, we might be seeing only our own words coming back at us, not words that tell us what they really think.
So they must have the opportunity to think with real things in their hands. But as they move up through the grades, we have think through practical work more carefully.
Practical work by learners has traditionally been seen as a way to establish science theory in the mind of the learner. There is an implied aim that the learner should discover the relationships between quantities/variables, but learners soon work out what they are supposed to “discover”, and the task then becomes one of getting the right result. For many learners, the motivating effect of small-group practical work fades as they move from primary school to senior school; the brightest learners may feel frustrated by having to “prove” what is quite obvious to them. For many other learners, practical work does not help them to form a clear understanding of theory because –
(a) the tricks needed to make the apparatus function and the demands of grasping the procedures in the worksheet represent an overload of information for them to deal with, and the basic ideas which the teacher wishes to make clear are often lost in the clutter of detail, and
(b) the previous experience and pre-conceptions that the learners bring to the prac may be reinforced by what they see in the apparatus – they explain the observations in terms of their own theories while writing down the explanation that the teacher expects to see. As a result, the learner may have two explanations that may be mutually incompatible – a personal explanation that makes more sense to him or her, and a teacher’s explanation that she should use in examinations.
We believe that science theory is taught much more effectively by a teacher who knows how to handle the apparatus, does convincing demonstrations, and asks probing questions before, during and after the demonstration.
What then is the place of learner practical work?
We believe that learners (those who intend doing sciences at university and those who do not) need practical experience with the real physical world:
- learners need to “get a feel” for materials and phenomena
- learners need to develop practical scientific skills and techniques
- learners need to think and work like a problem-solving scientist, technologist and engineer.
Remember that the sections on practical work apply to the whole year’s curriculum, not just the contextualising tasks
These practical activities need simple equipment and little time to do, but their power is in the discussion (learner-talk, not only teacher-talk) that should follow. Learners develop their science language and refine their concepts from vague ideas to more precise ones; this happens through language, in the explanations they construct and connections to other concepts they describe.
Examples of activities that build concepts by “getting a feel” for materials and phenomena, and promoting learner talk
These practical “getting-a-feel-for” activities we will call “experiences”. Examples of experiences in science are
- compressing air in a closed syringe
- watching a bead of water move outward along a tube connected to a bottle of air that is being warmed by a learner’s hands
- floating a bar magnet in a bowl of water and seeing it align north
- bending a length of wire repeatedly and feeling the temperature change in the bend
- growing a crystal
- estimating the weight of small objects after feeling the weight of 1 newton
- watching an indicator change colour in the wells of a micro-plate at increasing distances from a vial producing sulfur dioxide, to appreciate the effect of SO2 in the atmosphere
- feeling meths evaporate from one’s skin
- estimating the number of molecules in one breath,
This aim relates to the curriculum principle, “the word for the concept is not the concept”. A concept is built in a learner’s mind through repeated experiences with the phenomenon that it labels; for example, the word “evaporation” might be just the label a teacher gave to a single event, such as water on a wet path drying after rain. The concept of evaporation is much wider than this; the learner should have the experience of smelling a solid stick of mosquito-repellent, and seeing the solid material shrink over a period of a few days. And the learner should feel the difference in coldness on his skin when a smear of meths evaporates from his hand next to a smear of water. The learners should then describe or explain what they observed; their talk will require the concept of evaporation and so the word “evaporate” gains wider meaning and usefulness in their minds. Learners’ explanatory talk is the goal – it’s through using language that learners come to “own” the concept, have it ready for use in new contexts.
This kind of practical work builds Goal 2, construct [. . . and apply . . .] scientific and technological knowledge. Or whatever it is going to say
Assessment: This kind of activity lends itself to diagnostic and formative assessment but not to marking, lest learners fear to tell what they really think. But we could ask them to write ideas in a science thinking book, which teachers read but do not mark.
These practical activities we will call “exercises.” Here the aim is indeed to get the right answer or collect the right substance. Examples of such exercises in science are:
- estimating dimensions and other quantities such as the volume of liquid in variously-shaped containers e.g. work out by calculation the scale divisions on a conical rain-gauge
- using measuring instruments including rulers to work out areas and volumes
- measuring liquids using a micro-burette
- assembling an electric circuit with a lot of components and troubleshooting for bad connections and failed components
- measuring currents and voltages at points around a circuit and checking that all the voltage differences add up to the terminal voltage
- finding the concentration of a solution by titration as accurately as possible
- setting up the apparatus to collect carbon dioxide and testing for the gas
- collecting copper from copper oxide, confirming that one product is copper, and balancing the equation
- testing for certain ions in solution
- measuring and recording temperature changes in a solution and graphing the readings
- building models of molecules when given structural formulae
Prac exercises may reinforce theory and clarify the meaning of concepts, and that will be a good thing. However, the aim of these exercises is for learners to become good at the skills and techniques; consolidation of theory is the bonus.
Learners should be able to describe what they are doing, using correct scientific terms, and of course a teacher will ask the learners to make inferences from observations, predict the effect of changing a variable, and use other process skills such as those on page .
This kind of practical work builds Goal 1, Develop skills in scientific inquiry and problem solving.
Assessment: this kind of exercise activity lends itself to marking memos.
This is the central aim of practical work, and it rests on the two previous aims – developing tacit knowledge of phenomena and materials, and developing scientific/technical skills.
Acknowledging that our learners are probably not going to discover science knowledge that took the world’s best minds hundreds of years to grasp, we aim instead for them to make real personal discoveries, ones that matter to them because they are personal.
We look to creating opportunities for them to make personal discoveries as they work like problem-solving scientists, technologists and engineers. They need to be given (or they identify for themselves) problems in context of the physical world, including those that impact on the natural environment and people’s needs.
The notion of investigation is now broader than determining the effect of a variable, though it includes that purpose when appropriate. It includes problem-solving in the sense that technologists and engineers meet human needs for solutions and more effective ways of doing things. The problem, as in real life, is often not well-defined and the learners must reformulate it in terms that allow solution or investigation. Designing might involve controlling variables but might also call for the making of a device or a system; in each case, the findings or solution needs to be evaluated along the way and the learners might need to change their approach. Perseverance is required and it has to be learned.
These activities we will call “practical problems”.
Examples of practical problems begin from questions such as
- How you prevent corrosion on steel? Does your method work?
- Can you make conductive putty/prestik? What are its properties?
- A rural community complains that its water from the borehole tastes bad – bitter and sweet and salty all mixed up. Here are samples in bottles; do something to help them.
- Can you make a brick lighter and improve its insulation qualities?
- Do kitchen water filters work?
- What natural dyes did people in Africa use before synthetic dyes were introduced? Do those dyes work?
- How does soap work? Soap was made long ago – how? It does not work well in “hard” water; what makes water “hard”?
- Crystals can be grown big enough to be used as jewellery. What are the conditions from growing the best crystals?
- what are the possibilities of real circuits that you can create with a conductive pen? What kind of substances can you use to draw conducting lines? What is the teaching potential of this method of making circuits?
- which is the best dish-washing liquid? What is the optimum concentration?
- make a fire-extinguisher that is triggered automatically by fire or heat
- what is the difference between a fast-blow and a slow-blow fuse; how are they made? Can you make one of each type?
The examples could be teacher-generated or they might arise from the learners’ own interests.
These investigations are not convergent to a correct conclusion which the teacher and Google know already (such as “investigate the laws of reflection”). Instead these prac investigations are divergent, open-ended and may have several solutions, some better than others.
It’s important to note two points:
- conceptual understanding is always an issue; some prac tasks can hardly get started unless the learners understand some principles of chemistry or physics; this is especially so if they have to identify variables when doing a problem like “what is the effect of . . .”
- At the same time, these tasks can be done with partial understanding of the principles. The learners working on the problem may use formal science knowledge but like scientists, technologists and engineers they are quite likely also to use tacit knowledge – a feel for what material, what technique, might work. The problems require learners to produce a workable solution and this does not necessarily imply that they must explain why it works.
So the framework for practical problem-solving is one drawn from reports of the Assessment of Performance Unit in the UK, that had a strong influence on curriculum thinking
Types of problems needing a scientific, technological or engineering solution
“Decide which . . .” problems
There are many problems in which learners must decide which product or method is best for something. The initial problem might be, Which is the best dish-washing liquid to buy? They have to formulate the question more precisely, for example, by deciding what “best” will mean.
“Find a way to . . .” problems
The initial problem could be put as, how efficient is a small motor when used as a generator? The learners have to reformulate this question so that it is open to investigation and plan ways to measure the efficiency. Or, Can you make invisible ink?
“Find the effect of . . .” problems
These problems are more like the standard school science tasks that look at the effect of changing one or more variables. For example, the initial problem might be, Does the colour of the light that falls on a photo-voltaic panel have an effect on how it behaves? The initial question has to be reformulated into a question that is open to investigation, and the learners have to decide what to measure and how.
 An example of apparatus reinforcing a mis-conception is the activity of adding bulbs in series to a circuit. As each bulb is added, all the bulbs become dimmer. The explanation is that the teacher expects is that each successive bulb reduces the current. But many learners explain the dimming by saying that the bulbs are now sharing the current (unchanged) among them. The apparatus in front of them provides all the evidence they need – they can see the changes in brightness and “see” the current being “used up”, and “used up” equally between the two and then the three bulbs.