Motivation

Abstract

These and similar remarks are quite often heard by young people in school. In particular, due to the importance of school grades for student achievement in society, teachers are often led to threaten with the award of poorer school grades to discipline the students.

Appendices

Appendix A. Problems and Exercises

P2.1. Indicate examples of extrinsic and intrinsic motivation and discuss the differences between the two types of motivation. In what ways is intrinsic motivation possible in chemistry lessons? Describe three examples of teaching situations and appropriate motivation.

P2.2. Students’ misconceptions are particularly useful to create incongruities and anomalies and thus to offer motivating discussions in the classroom. Explain three self-selected examples in this context and illustrate the intended incongruity.

P2.3. Spectacular experimental effects easily motivate students to observe carefully. Choose two experiments, which are likely to create extrinsic motivation only, and find two other experiments which help to develop an intrinsic or substantive motivation.

P2.4. The start into a new topic of chemistry should be motivating for the students. Choose a topic and describe an introduction that (a) follows up on the previous knowledge of the students, (b) is characterized by an incongruity, (c) takes an everyday life reference, (d) is particularly motivating through self-activity of the students.

P2.5. The everyday language contains idioms that are not always scientifically correct, but provide motivation to think about and to correct them. Discuss this with three examples of your choice and suggest proper expressions for these issues.

Appendix B. Experiments

• E2.1. Constant Melting Temperature

  Problem: Students observe in their daily live that heating a substance increases the temperature. If a pure substance melts during heating, the temperature remains constant until the substance is completely melted: during the melting process the supplied energy is needed to breakup the crystal lattice of the solid substance. Students should recognize this in the following experiments and are motivated to think about energy and temperature.

  Material: Thermometer (200°C, with digital display), tripod and wire gauze, test tubes and beakers, wood clamp; ice, naphthalene (N), or stearic acid.

  Procedure: (a) The temperature of an ice–water mixture is measured. The mixture is heated one minute in the beaker, after a good stirring, the temperature is read off again.

  (b) A test tube is filled to a quarter with naphthalene and is heated with the Bunsen burner until all substance is melted; the melt is stirred with the thermometer and monitored. While stirring all the time the temperature is recorded every 30 s until the substance is condensing to a solid and completely solid again.

  Observation: As long as the ice melts, the temperature remains constant at 0°C. The naphthalene smells strongly of moth balls (since moth balls contain this substance). As long as there is a mixture of liquid and solid naphthalene, the temperature remains constant at 80°C, when the substance is completely solid, the temperature sinks down to room temperature.

  Disposal: The test tubes with the solid naphthalene are provided with a stopper and kept in the laboratory until the experiment is performed again.

• E2.2 Boiling Temperature of Water [16]

  Problem: Students often know only the scientifically reduced statement: “water boils at 100°C.” To show the relation of boiling temperatures and air pressure, the flask for boiling water can be connected to a pump to produce low air pressures and to measure lower boiling temperatures.

  It is also possible to replace the air in the boiling flask by water vapor and to condense it by cooling down with a wet cloth (see picture). By condensing of water vapor the pressure in the flask is decreasing, and the measured boiling temperature sinks to nearly 70°C. This results in the motivational incongruence for the students that the boiling temperature of water is not, as usual, reached by heating, but by “cooling.”

  Material: Round flask (500 mL) with side tube and valve, plug with thermometer (thermal sensor), water jet pump, tripod; water, boiling chips.

  

  Procedure: (a) The flask is filled with water to a quarter, it is brought to boiling (use boiling chips!) and the boiling temperature is measured at atmospheric pressure. The water pump is connected and the boiling temperature is measured again during the air extraction (caution vacuum, wear goggles!).

  (b) The water in the flask is heated to boiling for 1 min until the air has been completely replaced by water vapor (use boiling chips). The burner is taken away, the valve closed, the flask rotated 180° (see picture). A wet cloth is placed on the flask and the temperature recorded. The process is repeated several times, finally, the flask is rotated upright again, and the valve is opened carefully to fill the flask with air again (caution, wear goggles!).

  Observation: (a) Under reduced pressure thermometers show boiling temperatures below 100°C. (b) The water shows first the boiling temperature of 100°C. By cooling the flask the water starts to boil again, temperatures decrease down to 70°C. Finally, whistling air penetrates into the flask, and the flask is filled with air again.

• E2.3. Same Mineral Tablets, Different Gas Volumes

  Problem: Students know that carbon dioxide is dissolved in mineral water and that the same gas is released in small gas bubbles, when mineral tablets are dissolved in water. By collecting the gas of one dissolving tablet (see picture) students are not realizing that only a certain portion of the released gas occurs in the cylinder, the other part dissolves in water to saturation. If in addition a second tablet is dissolved in the presence of this saturated solution, the volume of carbon dioxide is nearly two times bigger than by the first tablet. This incongruity motivates students to reflect and to interpret these phenomena with the solubility of gases in pure water.

  Material: Graduated cylinder (250 mL) and matching stopper, glass bowl; mineral tablets (type “carbonate/citric acid”).

  

  Procedure: The cylinder is completely filled with water and with the help of the stopper placed pneumatically in the glass bowl half filled with water. Under the opened cylinder one mineral tablet is placed, and the produced volume of gas is marked or recorded. A second tablet is placed in the same way and the resulting gas volume is also recorded.

  Observation: The gas volume of the first tablet may result in about 70 mL, of the second tablet 70 + 130 mL: a total of 200 mL is observed (the actual volumes differ according to the brand of the tablets, they should be tested prior to use in the demonstration).

• E2.4. Extinguishing Fires of Fat and Metals

  Problem: Most fires in everyday life are extinguished with water. Therefore, students are usually unaware that it is not possible to extinguish burning metals, e.g., magnesium or burning fat with water – on the contrary, treating these fires with water causes terrible accidents. The experiments can be demonstrated either for a discussion of these safety aspects as well as a way for students to create a cognitive conflict and to solve it. In the experiments you can see that the burning fat at high temperatures of 300°C or more evaporates the added water instantly and an explosive mixture of vaporized fat and air burns with a big yellow flame. In the case of burning magnesium, the vigorous reaction of the metal with water forms metal hydroxide and hydrogen: this gas burns with a bright white flash. Instead of extinguishing both flames they are increasing to big fires – you have to eliminate the air from both fires, with sand in case of burning metals, and by closing the container in case of the burning fat.

  Material: Tripod and wire gauze; tea light with aluminum container, magnesium turnings (F), deionized water bottle with water.

  Procedure: (a) The wick of a tea light is cut off. The paraffin is heated strongly in the aluminum container until smoke is produced by decomposition of paraffin and the smoke is ignited. A water jet is aimed directly onto the burning paraffin. (b) A spoon of magnesium turnings are put together on the wire gauze and ignited by the strong burner flame. A water jet is aimed onto the burning metal (caution, wear goggles! For protecting the table against burning spots, cover the table with aluminum foil).

  Observation: (a) The burning fat creates an up to one meter high yellow flash; (b) the burning magnesium forms a high, bright white flash.

• E2.5. Blue Lightning Through Explosions of Gas Mixtures

  Problem: A historic show experiment shall demonstrate that striking experiments are usually associated with big emotions: even the Bavarian Queen wished to see the “Blue Lightning” for a second time and Liebig tried to perform the reaction of nitrous oxide and carbon disulfide again (see Sect. 2.2). Instead of nitric oxide he incorrectly used oxygen in the mixture with carbon disulfide and the round flask exploded injuring the king, the queen, and the experimenter himself. Today we use no round flasks for this experiment, but cylinders with parallel glass walls: those explosions cannot destroy the cylinder, the reactions are carried out safely.

  Material: Glass cylinder with cover glass, glass bowl, large test tube with a discharge pipe, plastic pipette (5 mL), burner, ammonium nitrate (O), carbon disulfide (F/T), oxygen (O).

  Procedure: In the preparation, ammonium nitrate is decomposed in a test tube by gentle heating; the resulting colorless gas of nitrous oxide is introduced pneumatically into the cylinder (under the exhaust hood!). The pipette is filled with 2 mL of carbon disulfide and emptied into the cylinder; the cylinder is covered with the cover glass. After removal of the cover the mixture is ignited by the Bunsen flame. The experiment is repeated with oxygen and carbon disulfide.

  Observation: A light blue flash appears and a specific sound is heard reminiscent of a barking dog (the experiment is therefore also called “barking dog”). In the second experiment a white flash is seen, which is accompanied by a loud bang.

• E2.6. Diet Coke Is Lighter Than Coca Cola

  Problem: The concept of density can be introduced by an effect, which surprises most students and therefore challenges them to explain the effect. Both cans are placed into ice-cold water: the can of Coca Cola drops down to the bottom of the container, the can of Diet Coke swims.

  You need to weigh both cans, to discuss the higher mass of 330 mL Coca Cola and to interpret this according to the high content of dissolved sugar in Coca Cola. Moreover, students are motivated to develop the idea of density: Coca Cola has the higher density compared to Diet Coke or Cola Light.

  Material: Large glass cylinder, balance, areometers (densities around 1.0 g/mL); 330 mL-can “Coca-Cola,” 330 mL-can Cola Light or Diet Coke, ice water.

  Procedure: The cylinder is filled to three quarters with ice water; both cans are placed into the water. Then both cans are weighed. Both samples of coke are heated to release the carbon dioxide; the densities of both solutions are measured by an areometer.

  Observation: The can of Coca Cola sinks to the bottom of the cylinder, the can of Cola Light swims on the surface. The can of Coca Cola weighs about 20 g more than the can of Cola Light. The density of the Coca Cola is a little bigger than 1.0 g/mL.

  Note: The production technology of canned Cola causes an air bubble in the can. These bubbles may differ from can to can and therefore the can of Cola Light may also sink in water. Try out some cans and choose the right ones before you show the experiment.

• E2.7. Ice Lets a Bottle Burst

  Problem: Another density phenomenon is provided by the anomaly of water: ice occupies a bigger volume than a portion of water with the same mass. We are very familiar with the fact that ice floats on water and we do not think about the fact that normally the solids sink in their melts: a candle sinks in its melt, a piece of lead sinks in the molten metal.

  To show the density anomaly of water, you can fill a container with cold water, close it and cool it to below the freezing point: the container bursts because of the larger ice volume.

  Material: Small glass bottle with screw cap, thermometer (−20–100°C); ice water, ice-salt freezing mixture.

  Procedure: The ice-salt mixture is produced and the temperature of −15°C is shown to the students. The bottle is filled to the brim with ice water and then is closed. The bottle is placed into the ice-salt mixture, after a few minutes the bottle is taken out of the mixture.

  Observation: The water freezes to ice and the bottle bursts into pieces of glass.

• E2.8. Black Carbon from White Sugar

  Problem: A most amazing phenomenon for students of any age is the reaction of white sugar and colorless sulfuric acid to black carbon: it can be shown that sugar is a carbon containing compound. Starting with the exciting sugar–sulfuric acid reaction, the students may be motivated to study the chemistry of carbon compounds in organic chemistry.

  Material: Beaker (100 mL), glass bowl, glass rod; sugar, pure sulfuric acid (C), water.

  Procedure: Sugar is added to about 3 cm high in the beaker and stirred with a little amount of water. It is covered with sulfuric acid about 3 cm high and the mixture is stirred briefly with the glass rod; the beaker is put into the glass bowl for protecting the table. Wait and observe.

  Observation: The white mixture turns black, water steam is formed with a strong hissing noise and swelling reaction, thereby the mixture heats up very strongly. It forms a black, porous substance in the form of a sausage, which can be up to 10 cm long. A sweet smell from the decomposition of sugar is noticeable.

  Disposal: The black substance – mixed with concentrated sulfuric acid – is carefully wrapped in aluminum foil and is disposed of in the container for solid waste. The beaker is rinsed with water and cleaned with paper.

• E2.9 Electricity from the Lemon

  Problem: To motivate for electrochemistry an experiment with a lemon is possible: two different metal strips are immersed into a lemon; using copper and zinc an electrical voltage of about 1 V can be measured with the voltmeter. If the same metals are used no voltage should be observed. The same phenomena can be shown with metal strips in sodium chloride solution; with different combinations of metals you can establish the redox series of metals. It is possible to show with a 2-V electric motor that electric current is produced by those simple electrochemical cells.

  Material: Beaker, knife, voltmeter, 2-V electric motor, cables, and alligator clips; sodium chloride, metal strips of copper, zinc, and magnesium (F), lemon.

  Procedure: (a) A lemon is prepared with a knife to insert two metal strips. Strips of copper and magnesium are placed into the lemon, they are connected by cables and alligator clips with the voltmeter, and the voltage is measured. (b) The beaker is filled halfway with a concentrated solution of sodium chloride. Two different metal strips are provided with cables and alligator clips and connected to the voltmeter; the metal strips are dipped into the solution and the voltage is measured. The experiment is repeated with different metal combinations and also with the same metals. The electric motor is connected as well.

  Observation: Dipping into the lemon, potentials of about 1.5 V are measured between copper and magnesium. In the salt solution the same voltage is observed, between zinc and magnesium smaller voltage values are measured. In case of the same metals, no voltage appears. For the higher voltages, the electric motor does work and shows the running electric current.

  Note: The juice of the lemon is a weak electrolyte solution: the electricity is not enough to run the electric motor. It succeeds, if two or three lemons are put in series.

• E2.10 Brass Name plate

  Problem: Students are motivated more strongly if they produce something that they can take home. They can produce their own brass name plate as an introduction into the topic “redox reactions with metals and acids.” This plate can be used not only at home, but students can also report their families and friends, how they have produced it: they may feel as experts in this area of chemistry, and may be proud of their competence.

  Material: Glass bowl, beaker (100 mL), pipette, brass plate or copper plate, candle, iron nail, knife; pure nitric acid (C), boiling chips, gasoline (Xn/F/N), filter paper.

  Procedure: One side of the metal plate is coated with heated liquid paraffin from the candle. With the iron nail you scratch a name or a desired figure deep into this layer of paraffin, so that the metal is exposed. You put the plate with the top layer of wax on a few boiling chips into the glass bowl and put it under the exhaust hood. In the beaker 5 mL of water and 10 mL of pure nitric acid are mixed and the mixture is dripped with the pipette onto the scratched parts of the paraffin layer. You wait about 10 min.

  Observation: The acidic solution reacts with the metal by forming a brown gas (nitric oxide) and a blue solution (copper nitrate solution). After removal of the remaining paraffin with the knife and gasoline-wet filter paper, the name or label is clearly visible in the metal plate.

  Disposal: The name plate and the glass bowl is rinsed with much water, the gasoline-wet filter paper is to be burnt under the exhaust hood.

• M2.1 Sphere-packing model of a salt crystal

  Problem: The manual production of structural models is highly motivating for many students, especially if they are allowed to take these models home. It is easily possible to illustrate the topic “composition of salts” with the example of the sodium chloride crystal structure, for example, the arrangement of sodium ions and chloride ions in the ratio 1:1 (see also detailed information in Chaps. 6 and 10).

  

  Material: Sodium chloride (rock salt) crystals, cellulose spheres (per student about 18 white spheres (diameter 30 mm) and 18 red spheres (diameter 12 mm)), glue.

  Procedure: The balls are glued together to layers as shown (see the picture), two times two layers are put in reverse order together to a square column. It is determined how many small balls touch one large ball and how many big balls touch one little ball. The produced model is compared with the original rock salt crystal. It should be discussed which aspects of the model are suitable, and which limitations of the model exist.

  Observation: The layers form a square column and show a closest sphere packing model of the sodium chloride structure. A large sphere is touched in the interior of the packing by six small spheres; a small sphere is touched by six large spheres. The ratio of spheres in the model is 1:1 (see also detailed information in Chaps. 6 and 10).