Introduction to Algorithms & Flowcharts

This topic thrives on movement and visual modeling because algorithms are abstract processes made concrete through physical action and structured diagrams. When students act out sorting or race to find items, they grasp why efficiency matters in real time, turning abstract Big O concepts into memorable experiences.

• Year 9
• Computing
• 3 activities
• 15 min–45 min

Learning Objectives

1. Design a flowchart to represent a simple, sequential process.
2. Explain the purpose of an algorithm in problem-solving.
3. Compare the clarity of flowchart instructions versus written instructions for a given task.
4. Identify the key symbols used in standard flowchart notation.
5. Deconstruct an everyday task into a precise sequence of algorithmic steps.

Think-Pair-Share

⏱ 20 min·Whole Class

Kinaesthetic Sorting: Human Bubble Sort

Line up ten students with different numbers on cards. Have them perform a bubble sort by comparing themselves to their neighbor and swapping if they are in the wrong order, repeating until the line is sorted. This helps students visualize the 'pass' mechanism and the inefficiency of the algorithm.

Prepare & details

Explain how a simple everyday task can be broken down into a precise sequence of steps.

Facilitation Tip: During the Human Bubble Sort, have students call out each comparison step aloud so peers can hear how many operations occur, reinforcing the inefficiency of O(n²) in real time.

Setup: Standard classroom seating; students turn to a neighbor

Materials: Discussion prompt (projected or printed), Optional: recording sheet for pairs

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Inquiry Circle

⏱ 15 min·Small Groups

Inquiry Circle: The Great Search Race

Provide one group with an ordered list of 100 items and another with an unordered list. Challenge them to find a specific item using linear search versus binary search. Groups record the number of 'guesses' or checks made to find the target, then present their findings to the class.

Prepare & details

Compare the benefits of using a visual flowchart versus written instructions for an algorithm.

Facilitation Tip: For The Great Search Race, shuffle the deck only after students have predicted how long binary search will take, making the failure obvious when the data is unsorted.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Stations Rotation

⏱ 45 min·Small Groups

Stations Rotation: Algorithm Efficiency Lab

Set up three stations: one for Merge Sort using physical cups, one for Binary Search with a phone book, and one for Linear Search with a deck of cards. Students rotate through, timing how long each takes and noting the pros and cons of each method on a shared digital document.

Prepare & details

Design a flowchart to guide someone through making a cup of tea.

Facilitation Tip: In the Algorithm Efficiency Lab, provide calculators so students can compute actual times for 10 vs. 1,000 items, linking their physical actions to numerical outcomes.

Setup: Tables/desks arranged in 4-6 distinct stations around room

Materials: Station instruction cards, Different materials per station, Rotation timer

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

Teaching This Topic

Teach this topic by first letting students experience the algorithms physically before introducing notation or vocabulary. Avoid starting with definitions of Big O; instead, let students measure and compare methods to discover inefficiencies themselves. Research shows that active, embodied learning cements understanding of algorithmic complexity better than passive explanation, so prioritize movement and real-world analogies over abstract graphs.

What to Expect

Students will explain the difference between linear and binary searches by timing their own searches, and they will compare sorting methods by physically acting out steps and recording data. Success looks like students using correct terminology to justify why one method is faster than another based on their observations.

Watch Out for These Misconceptions

Common Misconception

During the Human Bubble Sort, watch for students who assume any sorting method will require the same number of steps regardless of the data's initial order.

What to Teach Instead

After students act out bubble sort, pause the activity to reshuffle the deck randomly and repeat the process, asking students to compare the number of steps needed. This concrete comparison highlights how bubble sort's inefficiency grows with disorder.

Common Misconception

During The Great Search Race, watch for students who believe binary search can always halve the search space, even in unsorted data.

What to Teach Instead

Hand students a shuffled deck and ask them to perform binary search by calling out midpoints aloud. When they realize the process fails, have the class discuss why pre-sorting is a non-negotiable requirement for binary search.

Assessment Ideas

Exit Ticket

After the Human Bubble Sort activity, ask students to write a short paragraph explaining why bubble sort is inefficient for large datasets, using their own experience timing steps as evidence.

Discussion Prompt

During The Great Search Race, ask students to explain in pairs whether they would choose binary or linear search to find a name in a phone book, justifying their choice with reasons tied to the activity's outcomes.

Quick Check

After the Algorithm Efficiency Lab, present students with two pre-drawn flowcharts: one for bubble sort and one for merge sort. Ask them to identify which is which based on the number of steps and efficiency, explaining their reasoning.

Extensions & Scaffolding

• Challenge: Ask students to design a new sorting method and test it against bubble and merge sorts using a deck of cards or digital simulation.
• Scaffolding: Provide pre-labeled flowchart templates with missing steps for students to complete during the Human Bubble Sort activity.
• Deeper exploration: Introduce students to quicksort and have them compare its efficiency to merge sort by timing each method on a large dataset.

Key Vocabulary

Algorithm	A set of step-by-step instructions or rules designed to solve a specific problem or perform a specific task.
Flowchart	A diagram that represents the steps in a process or workflow, using different shapes to denote actions, decisions, and start/end points.
Sequential Process	A series of actions or steps that must be performed in a specific order, one after another.
Input	Data or information that is fed into a process or algorithm.
Output	The result or outcome produced by a process or algorithm after processing the input.