Measuring Mass Accurately

easuring, comparing and estimating with mass Draw out whether units are appropriate or inappropriate. Provide them with key benchmarks to support their future estimates. A paperclip weighs about 1 gram, a pound coin weighs about 10g and a bag of sugar has a mass of 1kg. Show pupils a set of scales with a dial scale. Discuss what it is used for. Clarify with the pupils how linear scales (e.g. spring balances) and circular representations link. Provide pupils with a paper plate to use to recreate a dial scale. Decide upon where 0 and 1000g (maximum value) will be placed. Ask them to mark on where they think 600g would go. Explore benchmarks they have used to help them e.g. 0, 250, 500 and 750 and 1000g. Then, ask pupils where they would place given masses on dials with a variety of scales. Pupils to find the masses of a variety of objects using a range of scales and spring balances. They express measures as kilograms (where the measure is kilograms and hundreds of grams only), grams and as mixed units. Using the handout (comparing mass), show a range of scales and different masses. Use questioning to explore the similarities and difference between the three images. Pupils then have hands-on, practical experience of measuring and comparing the mass of a range of everyday objects smaller and larger than 1kg. Pupils estimate the mass of each and place it on a blank number line. They then measure the actual mass and compare. Y4 - Step two Measuring, comparing and estimating with mass Remind pupils of the units and conversion facts for mass and capacity: 1000g = 1kg and 1000ml = 1l Use a 1kg bag of flour and a 1l bottle of liquid (or similar) to model these amounts. Pupils will use these to establish reference points. Ask related questions, for example: Model how to read scales for mass using the Year 3 example, ready to use weighing scales later in the lesson. They interrogate further scales through the following activities. The following challenges are for the pupils to explore while the teacher focusses on Year 3 learners: Comparing and estimating mass challenge: Use 4 different items, up to around 500g, for pupils to estimate the mass of. For example, an apple, a tin of beans, a large potato, their maths book.

Pupils first order them and then record an estimated mass for each. They can use something like a 500g bag of flour as a reference point and compare each item to it.
Then weigh each one in turn, starting with the item they thought was lightest in mass. After the first one has been checked, they can review their estimates for the others, trying to estimate accurately based on their developing reference points. Provide children with the Carroll diagram below and ask them to find an object in the classroom that would fit into each cell. Objects with a mass of… Less than 100g More than 100g Less than 1kg More than 1kg Which unit should we measure the mass of an elephant with? Grams, kilograms or something else? Where is 350g on each of these scales? Is it possible that: • I drank a litre of water during the school day? • A Year 4 child’s weight is one kilogram? Write down what the 3rd interval represents on each of your measuring tools. Where is 0 on each scale? What does 0g or 0ml mean? Can you think of a measurement scale where 0 does not mean an absence of something? On a thermometer 0 means no degrees but not no temperature. It means freezing. Image B shows electronic scales. This shows 4.2kg. 4kg is equal to 4000g and 0.2kg is equal to 200g. 4.2kg = 4200g. Image C shows that the scale is marked for each kilogram. Between 0 and 1kg, there are 10 markers which represent 100g each. Scales B and C show the same mass. What do you notice about the scales? In image A, I can see the scale goes up in 100g steps. There are 10 marks between each

Year Group

Year 3 (with Year 4 mixed in for differentiation and extension)

National Curriculum Links

Measurement: Mass
Compare and measure mass (in kilograms and grams) using scales, including those with dials and electronic displays.
Understand and use standard units of mass, including recognizing when units are appropriate or inappropriate.
Estimate and measure mass to support understanding of weight and capacity.

Learning Objectives (WALT)

WALT identify and use appropriate units to measure mass accurately (grams and kilograms).
WALT read and interpret linear and dial scales on measuring equipment.
WALT estimate and compare the mass of everyday objects using key benchmark references.
WALT express masses using grams, kilograms, and mixed units (e.g. 1kg 500g).

Success Criteria

I can explain why some units (grams or kilograms) are better to use than others depending on the object's size.
I can read measurements correctly on dial and linear scales.
I can estimate the mass of an object using benchmark weights like a paperclip (1g), a 10g coin, and a 1kg bag (sugar).
I can place mass values accurately on a scale from 0g to 1000g or more, using intervals.
I can measure and record the mass of classroom objects using scales.

Resources

Paperclips (~1g), pound coins (~10g), 1 kg sugar bag, 1 kg flour bag, 1-litre bottle of liquid
Dial scales with dials (spring balances and circular dials)
Paper plates, pencils, rulers (to create own dial scales)
Variety of classroom objects (apples, tins, maths books, potato, etc.)
Printed blank number lines (0-1000g) and Carroll Diagrams
Comparison handout with images of scales and different mass measurements (electronic, dial, spring balance)
Electronic scales (if available)
Dyslexia-friendly font handouts with visual supports and clear spacing

Lesson Outline (30 minutes)

1. Introduction & Engagement (5 minutes)

Show a paperclip, a pound coin, and a 1kg bag of sugar. Pose quick questions: "Which of these is heaviest? Which is lightest? Can we weigh these in grams or kilograms?"
Present WALT and Success Criteria on the board in simple language.
Explain key benchmarks: paperclip ≈ 1g, coin ≈ 10g, sugar bag = 1kg, and why benchmarks help us estimate.
Briefly show different scales (dial, spring balance, electronic) and ask: "What do these do?"

2. Modelling & Concept Development (7 minutes)

Demonstrate a dial scale with a pointer and circular display; show how 0 and 1000g might be placed on the dial.
Make links between linear scales and circular scales: "If a dial goes from 0 to 1000g with 10 intervals, how much does each interval represent?"
Use a paper plate to recreate the dial scale with students; guide them to mark 0 at 12 o’clock, 1000g opposite, and estimate where 600g fits.
Ask them which smaller benchmarks (250g, 500g, 750g) they would add to support their guesses.

3. Practical Activity - Estimating and Measuring (10 minutes)

Provide groups with 4 different objects (~up to 500g): apple, tin of beans, large potato, maths book.
Step 1: Pupils order these from lightest to heaviest and estimate the mass of each, using the 500g bag of flour as a reference.
Step 2: Pupils measure the objects on scales (dial or electronic, depending on availability), starting with what they think is lightest.
After measuring, allow pupils to discuss if their estimates were close and what helped them adjust their thinking.

4. Application and Reasoning (5 minutes)

Hand out blank number lines (0–1000g) and ask pupils to plot estimated masses of other classroom objects found by them.
Show a Carroll diagram and ask pupils to classify found objects by mass categories: less than 100g, more than 100g, less than 1kg, more than 1kg.
Pose higher-order thinking questions (whole class or paired):
"Which unit would you use to measure an elephant’s mass? Why?"
"Where is 350g on this scale? Why might 0g or 0ml be important to understand?"
"Can 0 on a thermometer mean no temperature? What does it actually mean?"

5. Plenary & Assessment (3 minutes)

Recap the WALT and success criteria.
Ask volunteers to share one benchmark and why it helps estimation.
Quick quiz: Show pictures of scales and ask what mass they display; pupils say if it is in grams or kilograms and if the unit is appropriate.
Collect their blank number lines and Carroll diagrams for informal assessment of understanding.

Differentiation

For Low Attainers & SEN:
Use highly visual, tactile materials (real objects, scales, coloured markers).
Give scaffolded sentence starters for explanations (e.g., "I think this weighs _____ grams because...").
Pair with more confident peer or teaching assistant for support. Use smaller steps, focus on one unit (grams) before introducing kilograms.
For Dyslexic Learners:
Provide handouts in dyslexia-friendly font with clear spacing and pictorial support.
Use colour-coded scales and benchmark cards to reinforce comprehension visually.
Allow oral explanation rather than written where possible.
For High Attainers & Year 4 Mix:
Challenge pupils to read scales with mixed units (e.g., 1kg 200g).
Estimate and compare masses beyond 1kg.
Explore conversions between grams and kilograms with word problems (e.g., "If this object weighs 4.2kg, how many grams is that?").
Encourage pupils to design their own dial scales with different maximum values and intervals.

Extension Activities

Create a "Mass Detective" challenge: Pupils find objects around school and justify which unit and scale type is best for weighing them.
Design a new measuring tool using household materials that show mass in increments other than 100g or 1kg and explain their reasoning.
Use interactive group quizzes with whiteboard apps or physical clicker responses to compare readings on electronic versus dial scales.

Teacher Notes

Emphasise the importance of understanding how '0' on scales relates to the absence of weight or substances and how that differs in other contexts (thermometer example).
Use consistent language around units (grams and kilograms) and reinforce conversion facts (1000g = 1kg).
Monitor pupils closely during practical tasks to correct misconceptions immediately, especially around scale reading and unit selection.
Reinforce that estimation improves with experience and knowledge of benchmarks, supporting pupils to build internal 'mental scales.'

This lesson plan is aligned with the National Curriculum for England, focusing on Year 3 objectives, and supports mixed attainment including Year 4 extension, ensuring all pupils gain a confident understanding of mass measurement and estimation.

Teaching Instructions