Skip to content
Teachers
Go to pupils
Choose exam board for KS4 Biology
Choose exam board for KS4 Chemistry
Choose exam board for KS4 Combined science
Choose exam board for KS4 Computer Science (GCSE)
Choose exam board for KS4 English
Choose exam board for KS4 French
Choose exam board for KS4 Geography
Choose exam board for KS4 German
Choose exam board for KS4 History
Choose tier for KS4 Maths
Choose exam board for KS4 Music
Choose exam board for KS4 Physical education (GCSE)
Choose exam board for KS4 Physics
Choose exam board for KS4 Religious education (GCSE)
Choose exam board for KS4 Spanish

Guidance

About us

      Insertion sort

      Download all resources
      Previous lesson
      Next lesson
      Skip to lesson content
      Share lesson with pupils

      Lesson details

      Learning outcome

      I can use an insertion sort to sort a list containing sample data.

      Key learning points

      1. An insertion sort groups the items of a list into two parts: a sorted sublist and an unsorted sublist.
      2. An item is taken from the unsorted sublist, compared to the items in the sorted sublist and put in the correct position.
      3. People often perform an insertion sort when they are putting objects into order, like books or cards.

      Keywords

      • Insertion sort - a sorting algorithm that progressively evaluates items in a list and inserts them into the correct place in an ordered sublist

      • Sorted sublist - sorted values held in the lower positions of the list

      • Unsorted sublist - unsorted values held in the higher positions of the list

      Common misconception

      An insertion sort is slower than other sorting algorithms.

      While other algorithms offer better time complexity for large, unsorted arrays, insertion sort can still be faster in practice for smaller and partially sorted lists.

      Teacher tip

      This lesson involves pupils performing an insertion sort on a list of data. It would be helpful if pupils had printed versions of the worksheets provided for this lesson to enable them to complete this task.

      Licence

      This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0
       except where otherwise stated. See Oak's terms & conditions
       (Collection 2).

      Lesson video

      Skip lesson video

      Loading...

      Prior knowledge starter quiz

      Download starter quiz questions (PDF)

      6 Questions

      Q1.
      Which of these best describes the process of splitting in merge sort?

      combining two sorted lists
      sorting the largest item
      Correct answer: dividing a list into smaller sublists
      comparing adjacent items

      Q2.
      What happens to unsorted sublists during merging in merge sort?

      Correct answer: they are combined into a single sorted list
      they are split further
      they are ignored
      they are compared but not combined

      Q3.
      What is the main advantage of merge sort compared to bubble sort?

      it uses less memory
      Correct answer: it is faster for larger data sets
      it is easier to write
      it requires fewer steps

      Q4.
      Which of these is a characteristic of a divide and conquer algorithm?

      Correct answer: splitting a problem into smaller parts
      solving the problem in one step
      ignoring smaller parts of the problem
      comparing adjacent items only

      Q5.
      Why does merge sort require extra memory?

      to store the largest item
      to compare adjacent items
      Correct answer: to store sublists during splitting and merging
      to remove duplicates

      Q6.
      Which of these is NOT true about merge sort?

      it works by splitting and merging
      it uses extra memory
      it is a divide and conquer algorithm
      Correct answer: it is always the fastest sorting algorithm

      Assessment exit quiz

      Download exit quiz questions (PDF)

      6 Questions

      Q1.
      What are the two parts of a list in an insertion sort?

      large values and small values
      even numbers and odd numbers
      Correct answer: sorted sublist and unsorted sublist
      numbers and letters

      Q2.
      During an insertion sort, where is the current item placed?

      at the end of the list
      at the beginning of the unsorted sublist
      in the middle of the list
      Correct answer: into its correct position in the sorted sublist

      Q3.
      What is one real-world example of using an insertion sort?

      searching for a word in a dictionary
      Correct answer: sorting books on a shelf
      combining two sorted lists
      finding the largest number

      Q4.
      Why might insertion sort be faster than other algorithms in some cases?

      Correct answer: it works well with small or partially sorted lists
      it requires no comparisons
      it skips unnecessary steps
      it uses less memory

      Q5.
      Place the steps of an insertion sort in the correct order:

      1 - compare the current item to the sorted sublist
      2 - insert the item into the correct position
      3 - repeat for all items in the unsorted sublist
      4 - list is fully sorted

      Q6.
      What happens if the current item is smaller than all items in the sorted sublist?

      it is ignored
      it is removed from the list
      Correct answer: it is placed at the start of the sorted sublist
      it is placed at the end of the list

      To help you plan your 10 computer science lesson on: Insertion sort, download all teaching resources for free and adapt to suit your pupils' needs...