Sorting like a computer

In this lesson, the students get to know a sorting algorithm (bubble sort) and carry it out according to the instructions, sorting everyday things (e.g. potatoes). This activity is suitable for elementary school children ages 6 to 8 and beyond. It does not require any digital tools (unplugged activity).

Goals of the activity:

The students

• practice computational thinking by breaking down the sorting process into individual steps

• get to know the term "algorithm" ("rule of action")

• create their own sorting algorithm, note it down and test it

• learn, read and execute a flowchart

• get to know and apply the sorting algorithm "Bubblesort"

• be able to explain why it makes sense for computers to use this algorithm

Duration: 2 hours (120 min) or two individual lessons

Note: The interdisciplinary topic of the lesson is " The potato". Therefore potatoes that the children have harvested the day before are used as sorting objects. The smaller potatoes are then boiled and tasted together.

Desirable prior knowledge: The children are already familiar with unplugged coding in the form of arrows and the principle that robots carry out individual steps one after the other.

Instructions:

A smaller amount of the potatoes is laid out in a circle. The children are given the task of sorting them according to size. Then another part of the potatoes is laid out and sorted. The process is verbalized in its sub-steps. The class is divided into groups of three. Each group is instructed to write down (or record) the sorting steps in such a way that a robot can follow these steps and carry them out. All work results are presented in a circle, the method of presentation and the process are discussed and, if possible, tested.

Now individual elements of a flow chart are presented and explained: start / end, instructions, query. Little by little, the bubblesort algorithm is developed together with the children until the (simplified) flowchart is complete. Individual sub-steps and queries are played through. With the complete flowchart some potatoes are sorted according to their size. Here one child is the robot, another reads the instructions, a third and fourth are the “counters” for the loops. If there is enough time, the sorting can be repeated in groups of four. The flowchart is then fixed and hung up in the classroom.

Material:

Items to sort (here: potatoes), a tape measure for cases of doubt, paper and pens for group work, colored elements for the cardboard flowchart, a large sheet of paper, markers, glue stick

(This activity is a contribution to the EU Code Week Online Bootcamp MOOC of the European Schoolnet Academy)

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