Comparing and Calculating

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Overview

Unit Title: Capacity Counts: Litres & Millilitres
Lesson Number: 3 of 3
Lesson Title: Comparing and Calculating Capacity
Year Group: Year 3
Class Size: 19 pupils
Duration: 60 minutes
Subject: Maths
Curriculum Link:

• Key Stage 2 (Year 3) – Measurement
  • Measure, compare, add and subtract: volume/capacity (litres/ml).
  • Continue to develop understanding of metric units.
  • Use standard units (litres and millilitres) to estimate and measure capacity using appropriate tools.

Learning Objective (LO):
To compare, add and subtract capacities using litres and millilitres in practical and real-world contexts.

Success Criteria:

• I can correctly compare two or more capacities using litres and millilitres.
• I can add and subtract capacities using appropriate units.
• I can work effectively in a group to solve real-life problems involving capacity.
• I understand when to convert between litres and millilitres.

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Resources Needed

• Measuring jugs marked in ml and litres
• Water tubs (or large containers for water access)
• Variety of containers (empty juice cartons, bottles, cups, beakers, milk cartons – labelled with volumes but not all full)
• Capacity sorting cards (pre-laminated visual comparisons – e.g. “Bottle A: 750ml” vs “Bottle B: 1.2L”)
• Whiteboards and pens
• Towels/sponges (for spills)
• Activity Sheets (Differentiated: mild, spicy, hot)
• Large class visual display of conversion facts (1L = 1000ml etc)
• Group aprons (optional!)

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Vocabulary

• Capacity
• Volume
• Millilitres (ml)
• Litres (l)
• Compare
• Convert
• Estimate
• Add
• Subtract

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Lesson Structure

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⏱️ 0–10 mins – Fluent in Five (Starter - Mental Maths Warm-Up)

Objective: Reinforce previous learning and build fluency in converting between litres and millilitres.

Activity: Conversion Quick Fire

Display 5 questions on the board. Pupils answer on mini whiteboards and hold up.

Examples:

1. Convert 2 litres to millilitres
2. What is 1500ml in litres?
3. Which is bigger – 0.75L or 750ml?
4. What do you add to 600ml to make 1 litre?
5. A bottle contains 3L of water. If 750ml is poured out, how much is left?

Encourage quick working out using doubling, number bonds to 1000, and estimation.

Differentiation Tip: Pair less confident pupils with a partner to whisper-answer before whiteboard show.

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⏱️ 10–20 mins – Direct Teaching: Visualise & Compare

Objective: Introduce comparing capacities using standard units, and recap converting between units.

1. Teacher shows two real containers: one marked “750ml”, the other marked “1L”. Ask:
   ❓ Which holds more? How do you know?

2. Guide class through real-time conversion:

   • “750ml is less than 1000ml, so it is less than 1L.”

3. Build anchor understanding with visual conversion chart on the board:

   1L = 1000ml
   0.5L = 500ml
   1.5L = 1500ml
   etc.
   

4. Pupils come up to sort picture cards into greater than / less than categories, justifying their reasoning.

Teacher Prompt:

• Use reasoning vocabulary: “I know __ is greater than __ because...”
• Discuss converting mixed units like “1L 250ml” with class.

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⏱️ 20–35 mins – Guided Group Activity: Capacity Comparisons Carousel

Objective: Practise estimating, comparing, and solving calculations involving capacity.

Set-Up:
5 activity stations (labelled A-E), each with:

• A measuring jug
• 2–3 different containers filled with water
• Problem card
• Record sheet

Station Example Problems:

• A – Compare the Containers:
  Measure and record the volumes of each container. Then, rank from least to greatest.
  (Between 150ml and 1.5L)

• B – Missing Capacity:
  One bottle holds 1L. If 600ml is poured out, how much remains?

• C – Add It Up:
  You have three containers: 250ml, 600ml, and 150ml. What is the total capacity if poured into one jug?

• D – Estimation Round:
  Using visual judgement only (no measuring), rank 3 containers. Then measure and see how close your estimate was!

• E – Real-Life Challenge:
  You’re filling a 2L jug to make orange squash for lunch. You’ve already poured 1L 150ml. How much more do you need?

Instructions:

• Pupils work in mixed ability groups of 3–4.
• Rotate every 3 minutes.
• Each pupil writes their workings and findings in a shared booklet.

Teacher Role: Float, support with conversions, probe reasoning with minor scaffolds e.g.

• “What do we need to do before we can add these together?”
• “Do we need everything in the same unit?”

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⏱️ 35–45 mins – Independent Practice: Mild, Spicy, Hot Tasks

Objective: Apply capacity knowledge through differentiated written problems.

Distribute worksheets (Mild, Spicy, Hot), based on pupil confidence from previous tasks. Ensure a fiction-based story or context for engagement.

Examples:

• Mild:
  Convert between litres and ml (e.g., 600ml = __L) and simple comparison questions.

• Spicy:
  Mixed word problems requiring conversion (e.g., subtract capacities given in different units).

• Hot:
  Multi-step capacity problems involving missing numbers and choices of operations.

Support Available: Prompt cards with conversion charts; teacher-guided table for those needing extra scaffolding.

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⏱️ 45–55 mins – Class Challenge: Capacity Relay

Objective: Use capacity skills collaboratively under timed conditions.

How It Works:

• Each team (4 groups) gets a track-style worksheet.
• Each pupil races to solve a problem on their team sheet.
• Once solved, ‘passes’ it on to the next pupil for the next question.
• Questions build in complexity and conversion.
• Timer set for 7 minutes.

Note: All problems involve real-life scenarios (e.g. preparing drinks, sharing water during a sports day).

🎉 Winning team gets a Water Wizard Certificate!

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⏱️ 55–60 mins – Plenary: What Did We Learn?

Return to carpet (or seated circle). Pose open-ended questions:

• What was the trickiest part of today’s lesson?
• What strategy did you use to compare two capacities?
• Why is it helpful to convert between litres and millilitres?

‘Exit Ticket’ Task:
Pupils write down one real-life situation where they might need to add or subtract capacities.

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Assessment for Learning (AfL):

• Observation of group work and peer discussion
• Notes from carousel tasks and team relay
• Review of independent worksheet accuracy
• Responses during plenary and exit tickets

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Differentiation

Support:

• Visual aids (capacity posters, conversion mat)
• Teacher-guided group (rotate during carousel)
• Sentence frames (e.g. “I think ___ is more than ___ because...”)

Challenge:

• Extra ‘Trickier Challenges’ on HOT sheets (incorporate 2L+, multiple conversions)
• Encourage pupils to design their own capacity problem for peers to solve

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Cross-Curricular Links

• Science: Investigating materials and their volumes
• Design & Technology: Recipe-based measuring
• Physical Education: Hydration station – tracking water intake with volume

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Teacher Reflection Prompts

• Were pupils confident converting between mixed units?
• Did the station tasks allow all learners to access the objective?
• Which pupils surprised you today?
• Any misconceptions observed around litre and millilitre conversion for review?

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“Maths becomes magical when it stops being numbers on a page and becomes water pouring, jugs tipping, and real-world questioning!”

🟦 Next Steps:
Consider launching a mini-project next week: pupils design their own healthy drink mix using given capacities and write instructions using volume and measurement vocabulary!

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Let me know if you'd like editable versions or printable labels for the stations!