Grams and Kilograms

Overview

• Age Group: Year 4 (8–9 years old)
• Duration: 45 minutes
• Class size: 30 students
• Curriculum Alignment:
  • National Curriculum for England:
    • Mathematics Programmes of Study - Year 4:
      • Measurement: Convert between different units of measure, including grams and kilograms.
      • Number: Recognise and use thousandths and relate them to tenths, hundredths and decimal equivalents (supports understanding metric conversions).
  • White Rose Maths Scheme: Summer Term, Week 1 (Measurement: Mass)

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Learning Objectives

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

• Understand that 1 kilogram (kg) = 1000 grams (g).
• Convert between grams and kilograms fluently.
• Explain their reasoning when converting between these units.
• Apply conversions to solve real-life measurement problems.

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Success Criteria

Pupils will:

• Identify when to convert between grams and kilograms.
• Correctly multiply and divide by 1000 when converting units.
• Justify their choice of calculation method verbally or in writing.
• Complete a range of conversion problems from straightforward to multi-step scenarios.

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Resources

• Whiteboards and pens for all pupils
• Interactive scale images or physical scales showing grams and kilograms
• Pre-prepared question cards with different weights in g and kg
• Worksheets with scaffolded conversion questions
• Example notebook/model answer on a large visualiser or whiteboard

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Lesson Breakdown

1. Introduction (10 minutes)

Engage:

• Start with a visual: Show two objects (e.g., an apple & a school bag). Ask, "Which one is heavier? How do you know?" Encourage learners to describe their reasoning.
• Draw attention to scales showing grams and kilograms. Demonstrate weighing both items and write their masses.
• Explain that weights can be measured in different units, grams and kilograms, and we often need to convert between them.

Teacher: "Can you think why it might be important to know how to change kilograms into grams or vice versa?" (e.g., recipes, shopping, science experiments)

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2. Targeted Questioning (Whole Class - Throughout Introduction and Modelling)

Using Bloom's Taxonomy, questions to deepen thinking:

• Remembering: How many grams are there in one kilogram?
• Understanding: Why do we multiply or divide by 1000 when converting?
• Applying: If an object weighs 3 kilograms, how many grams is that?
• Analysing: If I have 750 grams, can I say that is less than 1 kilogram? Why?
• Evaluating: Which is quicker or easier: multiplying or dividing to convert 2.5 kilograms to grams? Explain your choice.
• Creating: Can you create your own word problem involving converting grams to kilograms?

AfL - Use mini whiteboards to collect answers, looking for explanation, not just answers.

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3. Modelling (10 minutes)

Step-by-step example to copy:

Write in child-friendly language:

Example:
3 kg = ? g
We know 1 kg = 1000 g
So, 3 kg = 3 × 1000 = 3000 g

5000 g = ? kg
We divide by 1000 to go from grams to kilograms
5000 ÷ 1000 = 5 kg

Explain carefully: "We multiply when going from kilograms to grams. We divide when going from grams to kilograms." Emphasise the units.

AfL Point: Pause and ask: "Using your mini whiteboards, can you show me the conversion for 4.2 kg to grams? And now 7200 g to kilograms? Explain your method to your partner." Teacher circulates to check understanding and hears explanations.

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4. Main Activity – Gradually Increasing Complexity (15 minutes)

Task Part 1 - Basic conversions:

• Convert simple numbers such as 2 kg, 7.5 kg, 4500 g, 900 g into grams or kilograms.
• Pupils work independently using scaffolding sheets and mini whiteboards.

Task Part 2 - Applying conversions in context:

• Word problems involving weights, e.g.:
  • A watermelon weighs 1.3 kg. How many grams is this?
  • A packet contains 3500 g of flour. How many kilograms is this?
• Pupils explain their reasoning orally or in writing.

Task Part 3 - More complex problems:

• Two items weigh 750 g and 1.2 kg respectively. What is their total weight in kilograms?
• Convert weights shown on different scales in a ‘real life’ context, such as shopping or cooking scenarios.

Support and Challenge:

• Support sheets with number lines showing 0-2 kg in 100 g increments for visual learners.
• Challenge: Include decimal values, justifying conversions (e.g., "Explain how to convert 2.35 kg to grams.")

AfL: Teacher circulates, listens to explanations, asks probing questions:

• "Why did you choose to divide/multiply here?"
• "Can you explain how you know your answer is correct?"
• Quick thumbs up/down for self-assessment before moving on.

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5. Plenary (5 minutes)

Activities:

• Quick quiz using targeted questions with higher-order thinking:

  • “If I add 1500 g and 2.3 kg, what is the total weight in kilograms?
  • Explain or draw what happens to a weight when you convert it from kg to g.
  • Can someone explain the difference between dividing and multiplying when converting? Give examples.”

• Invite 3-4 pupils to share their thought process aloud.

• Highlight common mistakes spotted during the lesson and clarify misunderstandings.

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Common Misconceptions and Difficulties

• Confusing when to multiply or divide by 1000. Pupils might multiply both ways or divide both ways.
• Forgetting that 1 kg = 1000 g and sometimes thinking 1 kg = 100 g.
• Trouble with decimal conversions, e.g., 2.5 kg = 2500 g (place value issues).
• Ineffective verbal explanations lacking justification or using terms like "just because" without reasoning.
• Mixing units when adding weights (adding kg + g without converting first).

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Assessment for Learning (AfL) Points Summary

• Introduction: Use mini whiteboards to check recall of 1000 grams in 1 kg.
• Modelling: Use paired talk for explanations checking understanding of multiplying vs dividing.
• Main Activity: Teacher questioning with Bloom’s taxonomy style questions to probe reasoning.
• Plenary: Mixed questioning focusing on reasoning and justification. Peer explanation for assessment of verbal reasoning and conceptual understanding.
• Self and peer assessment via thumbs up/down after key steps.

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Alignment to National Curriculum (England)

• Key Stage 2 — Year 4 – Number – Measurement:
  "Convert between different units of measure [for example, kilometre to metre; hour to minute]" — Statutory requirement
  (Here applied to grams and kilograms for mass)

• Pupils engage with decimal notation as part of measurement understanding, which is fundamental for converting units with decimals.

This lesson plan integrates these statutory learning goals within a White Rose Maths progression to ensure conceptual understanding and fluency in measurement conversion, meeting expectations for Year 4 pupils.

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Designed to encourage deep reasoning, clear explanation, and practical application of converting between grams and kilograms.