Home Archivio 2015 12 - Anno XI Numero 2 Fizzy to the Max – a hands-on teaching unit based on Sherbet Powder

Fizzy to the Max – a hands-on teaching unit based on Sherbet Powder

Fizzy to the Max – a hands-on teaching unit based on Sherbet Powder

Prof Dr Claas Wegner

Bielefeld University, Universitätsstraße 25, Bielefeld, Germany


Phillip Weber

Bielefeld University, Universitätsstraße 25, Bielefeld, Germany


Stephanie Ohlberger

Bielefeld University, Universitätsstraße 25, Bielefeld, Germany

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Abstract

As a teacher, you have to think about how to get to your pupils while staying within their natural environment. In this regard, teaching units on everyday topics have proven highly successful. Concerning chemical issues, hands-on lessons about food and sweets are an approach worth trying. Hence, a unit on sherbet powder was developed within Bielefeld University’s project “Kolumbus-Kids”. The project’s students loved it, especially due to the fun of producing their own “fizzy powder”.

As we enjoyed watching the children become ever more excited and engaged during the unit, we want to provide you with the necessary background information so that you can benefit from our experiences as well and present the pupils with a good introduction into chemistry on a primary school level.

Keywords: sherbet powder, primary education, experiments, teaching unit

 

Theoretical Background

Being the most common leavening agent according to Myers (2007, p. 248), sodium bicarbonate is found in countless processes in the food industry, especially as baking soda and baking powder. Once this alkaline substance is added to a moist mix, a reaction with the acidic ingredients of such blends leads to the production of carbon dioxide (see chemical equation), which ultimately leads to the baked goods’ squishy texture.

NaHCO3 + H+ à Na+ (aq) + H2O (l) + CO2 (g)

In this case, H+ is supplied by the acid. As Myers (2007, p. 248) points out, sodium bicarbonate is a weak base with a pH of around 8. Such bicarbonate ions (HCO3-) have amphoteric properties, which means that they can act either as an acid or as a base and by that have the ability to neutralize both acids and bases.

Sodium bicarbonate, a white crystalline solid, tastes quite pleasantly and is therefore used in medicine, effervescent drinks and fruit salts (Kumar De, 2003, p. 244). It disintegrates into sodium carbonate and carbon dioxide when brought up to a temperature of about 250°C, though, and the Na2CO3 emerging here makes for a bitter taste. This, however, is adjusted by the addition of citric or tartaric acid in the end product, which transforms sodium carbonate into sodium citrate or sodium tartrate and thus removes the bitter taste (Nitin, 2009, p. 62). The addition of further acid can result in a rather sour flavor (Gaud et al., 2008, p. 143).

Teaching Unit

In our teaching unit, the students get to know about sherbet powder and its characteristics by simple experiments. As a special treat during the lessons, they can also produce their own. As the lessons are designed according to the Scientific Method, the students further practice and internalize professional ways of working. Thus, their learning outcome is based on their own discoveries, which leads to a better memorization of facts.

According to Wodzinski (2004, p. 127), experiments can excite children’s curiosity. This in turn leads to a better understanding of the scientific method and fosters the development of related methodological competences. Eventually, it is the science subjects’ task on a primary school level already to make children ask questions and conduct experiments in order to solve biological problems (Köstinger & Hartinger, 2006, p. 61). Even though it cannot compete with the actual scientific method, experimenting in primary schools can at least be seen as a rudimentary form of such working schemes (Wodzinski, 2004, p. 125). The single steps have to be repeated constantly and should be recalled by the teacher to support and guide the developmental process.

It is helpful to establish connections to everyday phenomena in order to connect subject content to the student’s environment. For the introduction of several chemical issues, food and diets are a good starting point. As early as in primary school, many pupils have strong dietary preferences resulting in an exaggerated consumption of sweets, as they often regard them as proper everyday food products. Their parents’ attempts to take steps against such habits often fall on deaf ears, which is why the children need to be supplied with basic knowledge about eating. Only then can they comprehend their parents’ statements. In this regard, sherbet powder provides a great opportunity to give the children an understanding of certain food ingredients and what these can do to a human’s body.

The reasons for using sherbet powder in classes are numerous. For starters, the children are already acquainted with this product due to their everyday life. Furthermore, lessons based on it fit the requirements of the curriculum, as they deal with substances and their transformation. The students accordingly get to know the powder as a mixture of substances whose characteristics can be examined via analysis, sorting and comparing. This initiates a questioning attitude and as a consequence thereof promotes the willingness to explore and investigate the food additive.

Due to the nature of the subject and the students’ foreknowledge about it, the children can work out answers to their questions fairly independently and actively. Most likely, different pre-concepts with regard to the fizzing of sherbet powder are present, as the children may have encountered similar characteristics in other liquids and drinks. Some might already mention carbonic acid and oxygen, but still it probably is not clear to them how the bubbles get into the powder. All these different ideas have to be considered and implemented into a research and discovery based way of learning.

In our teaching unit, the topic is introduced by a collection of research questions raised by the pupils. After that, a more detailed look is taken at the main ingredients of sherbet powder in that the pupils separate, taste and name the individual components with the aid of the list of ingredients provided on the packaging.

In a next step, the powder’s behavior when mixed in water is analyzed in order to explain the bubbling and fizzing. Special attention has to be directed at the question about which constituent exactly is the reason for the typical noise and the bubbles.

At the very end of the unit, the pupils prepare their own sherbet powder on the basis of what they have learned, hence making use of the newly acquired knowledge and in this way further securing it.

Experiment 1: Breaking sherbet powder down into its ingredients

Making use of the visual and the gustatory sense, the sherbet powder is spread on a black surface and investigated with magnifiers and toothpicks in order to separate the individual components, which can also be tasted. The pupils will find the following:

- Big, colorless, sweet-tasting crystals: sugar

- Small, white, soapy-tasting crystals: sodium bicarbonate

- Very small, colored, sour-tasting crystals: acids (tartaric or citric acid) coated with artificial coloring

They can also phrase hypotheses about the function of every ingredient, based on possible foreknowledge, such as that sugar is needed for sweetening, sodium bicarbonate is accountable for the fizzing and the acidic component makes for a nice coloring.

Experiment 2: Dissolving sherbet powder in water – what is causing the fizz?

With regard to the question about what makes sherbet powder produce bubbles, the pupils conduct an experiment, by this guaranteeing a purposeful analysis of the scientific phenomenon. They proceed according to the Scientific Method as they will first observe the coloring and fizzing of the water that occurs once sherbet powder is added. On that basis, hypotheses about the cause of the fizzing can be phrased, which will ultimately result in the students independently planning experiments. A possible approach is to fill three glasses half-full with water and then add single ingredients or a combination of them.

 

Experiment 3: Making sherbet powder

Letting the students make their sherbet powder allows for an application of the previously acquired, mainly theoretical knowledge. This proved particularly motivating, as the children had a lot of fun while doing so. For producing functioning saleratus, Reiss provides a list of ingredients:

- 1 tsp sodium bicarbonate

- 2 tsp citric acid

- 2 tsp (icing) sugar

- Optional: 5 drops of natural citric- or orange-oil (flavor) and food dye

After blending all these ingredients together, just add water to finish the process.

Conclusions

The presented teaching unit is a nice way of getting primary school students interested in chemistry as a school subject, as with the help of the experiments, they see its relevance in everyday life. The experiments are easy to conduct and do not require a lot of preparation, which make them ideal to try out in every classroom (see prepared worksheets in the appendix). Due to the fact that the experiments are conducted actively and independently according to the scientific method, the pupils are besides introduced to the general work principles in science lessons, which will proof beneficial for advancing in secondary school.

Bibliographic References

Gaud, R. S., Yadav, A. V., Yeole, P. G.,  Gokhale, S. B. (2008). Pharmaceutics. Mumbai:

Nirali Prakashan.

Kumar De, A. (2003). A Text Book of Inorganic Chemistry.  9th Edition. New Delhi: New

Age International.

Ministerium für Schule und Weiterbildung des Landes Nordrhein-Westfalen (2008).

Richtlinien und Lehrpläne für die Grundschule in Nordrhein-Westfalen. Frechen:

Ritterbach Verlag.

Myers, R. L. (2007). The 100 Most Important Chemical Compounds: A Reference Guide.

Westport: Greenwood.

Nitin, K. (2009). Longman Science Chemistry 10. New Delhi: Dorling Kindersley.

Reiss, J. (2002). Alltagschemie im Unterricht. 6th Edition. Cologne: Aulis-Verlag Deubner.

Köster, H. & Hartinger, A. (2006). Kann eine Colaflasche schwitzen? Experimentieren als zentrale Lernstrategie naturwissenschaftlichen Lernens. Grundschule, 7-8, 60-63.

Wodzinski, R. (2004). Experimentieren im Sachunterricht. In A. Kaiser & D. Pech (Eds.). Basiswissen Sachunterricht. Unterrichtsplanung und Methoden (pp.124-129). Baltmannsweiler: Schneider Verlag Hohengehren.

 

Appendix: Worksheets (here)

 

 

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