Measuring Mass Matters

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Overview

Unit: Measuring Up: Units Mastery
Lesson: 4 of 6
Duration: 60 minutes
Age Group: Year 7 (Age 11–12)
Class Size: 22 students
Curriculum Reference:
KS3 Mathematics – National Curriculum for England:

• Ratio and Proportion: use standard units of mass, using decimal notation to two decimal places
• Measurement: use and convert standard units using decimal notation, including between grams (g) and kilograms (kg)

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Learning Intentions

By the end of this lesson, students will be able to:

• Accurately read mass from both kitchen and bathroom scales.
• Convert between grams and kilograms confidently.
• Estimate the weight of common everyday items and verify through measurement.
• Discuss the relevance of mass in everyday life, particularly in cooking, sport, and health contexts.

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Success Criteria

Students will:

✅ Record mass readings using grams and kilograms correctly.
✅ Convert masses using decimal notation (e.g., 1.25 kg = 1250 g).
✅ Participate actively in practical measurement activities.
✅ Reflect on the use of mass measurements in their own lives.

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Vocabulary

• Mass
• Grams (g)
• Kilograms (kg)
• Estimate
• Convert
• Scale

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Resources Required

• Digital and analogue kitchen scales (at least 4 sets for group work)
• Bathroom scale (at least 1, placed on a safe, flat surface)
• A set of weighed everyday items:
  • Apple
  • Bag of sugar/flour
  • Water bottle
  • Textbook
  • Pack of cereal
  • Random unlabelled objects in sealed bags for estimation challenge
• Conversion charts (for reference group activity)
• Whiteboards and markers (class set)
• 22 ‘Mass Investigator’ worksheets (provided below)
• Projector and presentation slides (optional but recommended)
• Stopwatch/timer

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Lesson Structure

⏱️ Starter: Connect (10 minutes)

“Mass Detective!” Warm-Up Task
Display three mystery object silhouettes on the board. Ask:

• Can you estimate the mass of each?
• Which one do you think is heavier, and why?

Facilitate brief class discussion, taking a few confident predictions.

On mini whiteboards, students write the mass of a common object (e.g. "How heavy is a bottle of water in kilograms?"). Reveal actual masses and discuss how accurate the class estimates are.

🧠 This activates prior knowledge, connects to real-life contexts, and primes visual understanding of volume vs. weight.

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🎯 Main Input: Teach (15 minutes)

Part A: Demonstration with Scales (7 mins)
Teacher-led demonstration: Using a kitchen scale, weigh an apple and a bag of sugar. Flip between grams and kilograms (e.g. 1050g = 1.05kg).
Pose questions:

• Which is heavier?
• Why might we use kilograms instead of grams sometimes?

Part B: Direct Teaching (8 mins)
Use modelling and the whiteboard to teach how to:

• Convert from grams to kilograms and vice versa.
• Read different types of scales (some dial-based, others digital).

Ensure pupils understand that:

• 1000 grams = 1 kilogram
• Decimal notation is key for accuracy (e.g., 1500g = 1.5kg)

Provide examples and ask students to convert:

1. 2300g = ? kg
2. 2.6kg = ? g
3. 150g = ? kg

Check answers as a class, correcting misunderstandings.

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🤲 Activity: Apply (25 minutes)

Mass Investigator Challenge

Divide students into groups of 5–6 (4 groups).
Each group will complete rotating practical stations:

Station	Activity	Resources
1	Estimate then weigh 5 items. Record actual and estimated mass.	Kitchen scales, labelled objects, worksheet
2	Convert between grams/kilograms. Timed relay! Each student completes 1 card.	Conversion card deck, stopwatch
3	Human mass stations. Estimate weight, then use bathroom scale.	Bathroom scale, clipboard
4	MYSTERY MASS BAGS – guess weight and rank by heaviest to lightest, then measure to confirm.	Unlabelled objects in bags

Tip: Allocate 5 mins per station, with 1-minute transition. Assign one group leader per team to rotate clockwise. Use a bell/timer for clean transitions.

Each student fills their ‘Mass Investigator’ Worksheet, including:

• Estimations
• Actual measurements
• Conversions
• Reflections on surprising results

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💬 Reflection & Whole-Class Discussion (5 minutes)

Back at desks, ask students:

• Which item was heavier than expected?
• Why is mass important in everyday life?
• Where would we need to use precise measurements like grams?

Facilitate discussion linking mass to:

• Cooking and recipes
• Health and fitness (body mass)
• Postage and packaging

Give bonus scenario:
“If 1 litre of water weighs around 1 kg, what would 2.5 litres weigh?”

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✅ Plenary: Exit Ticket (5 mins)

Students must complete one of the following and hand in on a sticky note/on their whiteboard:

• One thing I learned today about mass...
• A real-life job where mass measurement is important is… because…
• Convert: 1.75 kg = ? grams

Teacher collects for AFL (Assessment for Learning) insight into understanding.

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Differentiation

Support for Lower Ability

• Use scales with large digital displays
• Partner support during activities
• Visual conversion charts provided for guidance
• ‘Starting Conversion Starters’ worksheet for scaffolded conversion

Challenge for Higher Ability

• Extension: Create your own word problem involving grams and kilograms
• Real-life case scenario: “Your cake recipe calls for 250g flour. You only have scales in kg!”
• Assist peers at mystery mass challenge and justify reasoning using maths vocabulary

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Assessment Opportunities

• Observation at practical stations
• Review of Mass Investigator worksheets
• Exit Tickets for summative understanding
• Questioning during plenary discussion
• Conversion task responses during main input

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Home Learning (Optional Extension)

Kitchen Maths Challenge
Students choose 3 household items and:

1. Estimate their weight
2. Weigh them at home (if possible, using kitchen scales)
3. Record their findings in a table
4. Convert from grams to kilograms

Parents/carers can sign to confirm – this builds home-school links and uses maths in a meaningful domestic context.

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Reflection for Next Lesson

Use worksheet and exit ticket data to inform targeted support and adjust pace for Lesson 5: "Volume and Capacity Conversions".
Focus particularly on decimal conversion fluency if patterns of misunderstanding are observed.

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🧡 Mass isn’t just for the classroom — it's in your shoes, your sandwiches, and your suitcase. Let’s keep those eyes weighing wherever we go!