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Year 10
OCR

Insertion sort

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

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New
New
Year 10
OCR

Insertion sort

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

Download all resources
Share activities with pupils

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Lesson details

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.


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

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.
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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

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Prior knowledge starter quiz

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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

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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