‘Named Small but Doing Great’: An Investigation of Small-Scale Chemistry Experimentation for Effective Undergraduate Practical Work

Abstract

In theory, practical work is an established part of university-level chemistry courses. However, mainly due to budget constraints, large class size, time constraints and inadequate teacher preparations, practical activities are frequently left out from chemistry classroom instruction in most developing countries. Small-scale chemistry (SSC) experimentation in which one uses miniature chemical equipment can drastically reduce quantities of chemicals used during experimentation, which can help overcome some of the barriers preventing practical work in the chemistry classroom. This study evaluated the effectiveness of using miniature chemical equipment at the undergraduate level in increasing students’ understanding of chemistry concepts as well as in improving their attitude towards chemistry practical work. Two comparable groups of first-year students who enrolled for a Practical General Chemistry course participated. A quasi-experimental design was employed in which the experimental group (N = 49) used the SSC approach while the control group (N = 52) followed the traditional approach for over 8 weeks. Data were gathered using chemistry tests, attitude and perception questionnaires and interviews. Findings showed that the SSC approach was as effective as the traditional laboratory approach in improving students’ attitude towards practical work, but more effective in enhancing students’ understanding of chemistry concepts. More interestingly, SSC was positively accepted by both students and instructors as an effective strategy for teaching first-year undergraduate chemistry practicals. Some shortcomings of the approach were also identified.

Appendix: SSC Experiment, Sample (Source: MyLab, 2012)

• Experiment 6: Effect of concentration on reaction rate

• Objective: to observe how the changing concentration of a reactant will affect the speed of a reaction.

• Theory: The rate of a chemical reaction can be measured in many ways. In reactions were gases are involved the rate can be monitored by measuring the pressure change in the system. Measuring how fast the colour of a solution changes is another method. Colorimeters are capable of measuring the amount of light passing through a solution containing colour absorbing species. What other methods do you know? In this experiment, hydrochloric acid reacts with sodium thiosulphate (Na₂S₂O₃) to produce colloidal sulphur as one of the products.

  $$ 2\mathrm{H}\mathrm{C}\mathrm{l} + {\mathrm{Na}}_2{\mathrm{S}}_2{\mathrm{O}}_3\to {\mathrm{S}\mathrm{O}}_2\left(\mathrm{g}\right) + \mathrm{S}\left(\mathrm{s}\right) + 2{\mathrm{Na}}^{+} + 2{\mathrm{Cl}}^{-} + {\mathrm{H}}_2\mathrm{O} $$

• Apparatus: MYLAB apparatus stand, 10 test tubes, test tube holder, spatula, thermometer, water bowl, glass beaker

• Materials: stopwatch, and two sheets of graph paper

• Chemicals: Hydrochloric acid (6 mol.dm⁻³), sodium thiosulphate and water

• Safety: Hydrochloric acid can cause burns and gives off a vapour which is irritating to the respiratory system. Be careful when you work with glass apparatus

• Procedure: Set up the apparatus as shown in the sketch below

  

• 1. Put four test tubes in the apparatus stand as shown on the sketch. Dissolve 5 spatulas of sodium thiosulphate in 10 ml water in the glass beaker

• 2. Prepare four diluted solutions of sodium thiosulphate as follows in the four test tubes. Use the syringe or the pipette to measure the volume accurately.

  Test tube	Sodium thiosulphate, Na2S2O3	water
  1	2 ml	0 ml
  2	1.5 ml	0.5 ml
  3	1 ml	1 ml
  4	0.5 ml	1.5 ml

• 3. Make four dark pencil marks (X) on a paper and put it beneath each of the four test tubes.

• 4. Use a stopwatch to time the disappearance of the black mark under the test tube. While looking from the top of the test tube through the solution in the test tube, start the stop watch immediately after you have added 2 drops of diluted HCl with a propette to test tube one. Stop the watch when the mark disappears completely.

• 5. Now, repeat step 4 with test tubes 2, 3, and 4 respectively and tabulate your data.

Post-lab exercise

• 1. What is the significance of adding varying amounts of water (1 ml to 4 ml) to the four test tubes?

• 2. Write the reaction of this experiment. What type of reaction is this?

• 3. Which one of the products of this reaction can be used as an indicator of the rate of the reaction (explain why the other factors cannot be used)

• 4. How do you prepare a 10 ml and 6 mol.dm⁻³ solution of HCl from an 11.65 mol.dm⁻³ stock solution of HCl.

• 5. Write the possible sources of error in this experiment?

• 6. What do you learn from this experiment?

• 7. Suggest any other method to do this experiment or suggest a similar experiment with different reagents, involving the factors that influence the reaction rate.