Merge sort: Split into single items, then merge them back in order. A complete, ready-to-teach 90-minute lesson for OCR GCSE (9–1) Computer Science J277, spec 2.1.3, Paper 2 (J277/02). Download it and teach it, no preparation needed.

WHAT’S INCLUDED
• PowerPoint (88 slides) with step-by-step animated worked examples and click-to-reveal answers
• Worksheet with three levels: Bronze (grades 2–4), Silver (4–6) and Gold (6–9)
• Exit tickets with a confidence scale
• Teacher answers with full working

LESSON FLOW
• Recall (6 questions) and starter (4 questions), timed
• Objectives, key words and a key facts slide
• Part A: Merging two lists · Part B: The whole merge sort · Part C: Odd lists, code, compare
• Each part: method, I do, We do, You do (6 mini-whiteboard questions; the score picks the worksheet level), timed worksheet task, answers
• 4 original exam-style questions (9 marks) with a mark-by-mark walkthrough
• Exit ticket

LEARNING OBJECTIVES
• To know: The two stages of a merge sort: split into single items, then merge into sorted lists
• To understand: Why merging two sorted lists gives a sorted list, so no extra sorting step is needed
• To be able to: Show every stage of a merge sort on a data set and compare it with bubble sort

WHY TEACHERS LIKE IT
• Visual first: every worked example builds one click at a time
• Teacher notes on every slide: timings, what to say, and the mistakes examiners report
• Every answer checked: calculations, traces and code are worked out by running them
• Exam-style questions written to match J277 command words and mark tariffs

Key words: Merge Sort, Merge, Split, Sub-List.
Part of Unit 7: Algorithms. Also available in the Unit 7 bundle and the full course bundle.

Original resource by Mo² (Mo Squared Resources). Not endorsed by OCR.