WWW Site for John Lawrence Bencze, Associate Professor, Science Education, OISE/University of Toronto

Procedural Education
Developing Expertise for
'Judging Ideas'

Developing Expertise
for Experimentation

Welcome! This page provides perspectives, general practices and links to resources for helping students to develop expertise for conducting self-directed experiments in science & technology. Experiments can be used for Judging Ideas, which is a major phase of my constructivism-informed pedagogical framework. If you have comments, questions, suggestions, resource ideas, etc. about anything here, please write to me about them. Thanks.


NoST/STSE Regarding Experimentation
When scientists & technologists seek empirical support for claims about phenomena, they often use experimentation. This is an approach that should be distinguished from 'studies,' about which perspectives and practices are elaborated elsewhere. As indicated in the figure at right, an experiment is an activity in which the one or more independent ('cause') variables are forced to change. To develop ideas about food decay, for example, we could conduct and experiment by steadily increasing the temperature (independent variable) of food-bacteria mixtures and measure the rate of food decay (dependent ['result'] variable). Instead, we could find some food-bacteria mixtures in nature, measure their temperatures and determine the rate of decay in each case. This latter type of inquiry would be a study, which is a type of inquiry in which the independent ('cause') variable is allowed to change naturally. It also would be a correlational study, because we would be comparing (correlating) how changes in one variable (e.g., natural temperature changes) may affect changes in another variable (e.g., rate of decay).

Which of these two sorts of investigations inquirers choose to use depends on various factors. Experiments often produce quick results and, for that reason, they may be preferred over studies. Sometimes, however, experimentation is impractical and, therefore, studies are necessary — as in the case of much of astronomy, for example. Perhaps more significantly, it often is ethically problematic to conduct experiments in some cases. With every experiment, there is a risk of negative side-effects of forcing a variable to change. Asking volunteers to smoke different numbers of cigarettes in order to determine cigarettes' effects on human heart rate may work, but it risks giving them lung cancer! — along with other possible unexpected negative side-effects. Such issues are elaborated below and through my page about studies.

Strategies for Helping Students to
Develop Expertise for Experimentation

There are various approaches for helping students to develop skills they could use for conducting experiments, but resources here are based on the constructivism-based approach at Skills Pedagogy. Resources for the Modelling & Practice stages of this framework are provided on this page, through the links at right. Resources for helping students to express their pre-instructional skills for science inquiry (including experimentation) are provided at Expressing Inquiry Skills.

Interactive Teacher Demonstrations: Teachers can engage students in discussions, in a Socratic style, usually involving manipulation of concrete phenomena in an experimental way. Four common techniques are illustrated below. During and after such demonstrations, teachers should ensure students at least begin to develop understandings of important principles relating to experimentation — including, for example, those ideas described briefly at right.
Characteristics of Experimentation
  • experimentation involves forcing a 'cause' (independent) variable to change;
  • a cause variable should be changed in regular increments over a reasonably wide range;
  • the experiment should be repeated at least once; this may involve having duplicate preparations for each value (e.g., 5 set-ups at each temperature) of the cause variable;
  • other known possible cause variables should be kept unchanged or at a 'normal' level;
  • where feasible, quantitative and qualitative observations of cause and result (dependent) variables should be made;
  • each observation (i.e., measurement and/or description) should be repeated;
  • where feasible, related, comparable result variables (e.g., leaf colour & thickness) should be studied;
  • experimentation should be used in conjunction with theory-development; e.g., data from experiments may not mean much or be misleading without appropriate theory.
  • it should be made clear that experiments can be used to evaluate possible WISE Problems.

Ball & Ramp: This demonstration simulates a ski ramp or playground slide. The idea is to explain the set-up (shown at right), demonstrate what it can do, relate it to skiing or sliding, and get students to help you design a 'fair' test. Variables affecting distance travelled may be: angle of ramp, weight of ball, force of release of ball, diameter of tube, etc. Through trial-and-error and discussion, students generally can develop understandings of the sorts of points list above. Elastic Band Launch: This demonstration should only be chosen when working with students who have the maturity to handle its 'fun' aspect. Again, show students how to 'launch' elastic bands and engage them in a discussion about what test(s) can be conducted with them (perhaps using bands of different lengths and thickness). As a WISE Problem application, you might discuss these as rocket tests.
Alka Seltzer: Alka Seltzer™ breaks down to produce CO2 gas upon contacting water. The amount of gas formed tends to depend on the water temperature, the acidity (increased by adding vinegar), surface area of tablet (by breaking it into smaller pieces), among others. Remember to use a large cylinder (or clear, plastic bottle); One seltzer tablet easily displaces more than 100 mL of water (The container of water is inverted in the tub by cupping a hand over its opening!). A possible WISE Problem connection could be made by asking students to read the ingredients list for the seltzer and research their effects.
Balloon Activities: There are several variations of using balloons for pointing out the sorts of characteristics of experiments as those listed above. Balloons of different sizes and shapes can be shown to students. The teacher can ask students what can be done with them to learn more about them. They suggest inflated them and letting them  go. This lends itself to looking at distance travelled, loops completed or sound made, etc. Or, students might suggest tying the balloons off, inflating them to different volumes and letting them drop. They also might suggest using them to create static electrical charges in people's hair. Try to work with some of the students' suggestions. Others can be reserved for guided practice, below.

Student Reading: Teachers should encourage students, depending on their age and stage of development, to read various summaries and descriptions of experimentation such as the description @ Sample Experimental Project. Many of these are available on various Web sites, accessed through Skills Ed. Resources. Many textbooks also provide information about the nature of experimentation. All such resources should be used with caution, paying attention to the extent to which they provide realistic portrayals of experiments and their role in science and technology. The extent to which they suggest that knowledge buiding is an inductive/empirical process often is a problem, for example.

Multimedia References: Students can learn about the nature of experimentation through films, video recordings and various animated Web pages on the internet. Teachers can check their school, school district and union libraries. Web-based resources are available through Skills Ed. Resources. Again, all such resources should be used with caution, paying attention to the extent to which they provide realistic portrayals of experiments and their role in science and technology. The extent to which they suggest that knowledge buiding is an inductive/empirical process often is a problem, for example.

Student Practice
Students should be given several opportunities to gain some practice in developing expertise regarding experimentation. Generally, these may involve: i) designing & conducting experimental inquiries and/or ii) analyzing & evaluating completed inquiries. As students work through the various activities, they should have opportunities to interact with peers. Teachers also should interact with students on a regular basis, questioning them about what they are doing and reasons for their actions. Generally, teacher interactions should encourage students to develop independent experitse, rather than developing a reliance on the teacher for the 'right' answers, methods, etc. Some specific suggestions for these sorts of activities are provided at right, along with links to relevant resources.
  • A common and pragmatic approach is to provide students with some sets of variables involving phenomena for which equipment and materials are relatively easily available. Some possible sets of variables are provided @ Expt Design Exs. These activities could be used in conjunction with a guide sheet that provides some suggestions about experimental design, such as @ Expts Template.Other examples are provided @ Expts Practice and @ Expt Purpose & Design.
  • In terms of analysis & evaluation of projects involving experimentation, and excellent source is students' science textbooks, which tend to have numerous 'labs' or 'inquiries' that involve experimentation.
All rights reserved, J. L. Bencze, 2008.