You will learn
- Say that mass tells how heavy something is.
- Use kilograms and grams.
- Compare the mass of two objects.
- Change kilograms to grams.
Version 0.2 · expanded edition · built from cited public sources Content is based on the official frameworks and sources listed under Sources and standards. No official endorsement is claimed. Written in the style of common primary school assessments. No exam result is promised.
Student lesson
- Mass tells how heavy something is.
- We measure mass in grams and kilograms.
- 1 kg = 1,000 g.
- Compare and add masses in the same unit.
Words to know
How heavy something is.
A unit of mass.
A small unit of mass.
A scale that compares mass.
1. Discover: rice and beans
A bag of rice and a bag of beans are the same size. Which is heavier? How can a market seller find out?
2. Understand: mass
Mass tells how heavy something is. We measure it in kilograms (kg) for heavy things (a bag of rice) and grams (g) for light things (a pencil is about 10 g).
1 kg = 1,000 g. So 2 kg = 2,000 g.
A balance compares masses. The heavier side goes down. 5 kg of rice is heavier than 3 kg of beans by 2 kg.
Idea 1: Mass
Mass tells how heavy something is. A balance compares the mass of two objects: the heavier side goes down.
Idea 2: Units
The gram (g) is a small unit. The kilogram (kg) is bigger. 1 kg = 1,000 g. A pencil is measured in grams and a bag of rice in kilograms.
Idea 3: Change and compare
2 kg = 2,000 g. 500 g + 500 g = 1,000 g = 1 kg.
Why change? To compare 4 kg and 400 g, use the same unit: 4,000 g is more than 400 g.
3. Worked examples
Example 1 (I show you): Choose the unit
What unit would you use for a bag of rice?
- A bag of rice is heavy.
Answer: Kilogram
Example 2 (We do it together): Change
2 kg = ? g
- 2 × 1,000.
Answer: 2,000 g
Example 3 (You try): Add
500 g + 500 g = ?
Show the steps and answer
- 1,000 g is 1 kg.
Answer: 1 kg
Did you know?
A litre of water has a mass of about 1 kilogram.
Why this matters
We use mass to buy food, weigh luggage and measure ingredients.
4. Explore: balance game
You need a balance or a hanger and two bags.
- Put two objects on the balance.
- See which side goes down.
- Order three objects from lightest to heaviest.
- Say the units a seller would use.
Think about it: what did you notice?
The heavier side goes down.
5. Practise
Say it in a sentence
Use these starters when you talk about the lesson. Say them out loud.
- ___ is heavier than ___.
- 1 kg = ___ g.
- I use ___ for a ___.
- The difference is ___.
Guided practice
Question 1. 1 kg in grams?
1,000 g.
Question 2. 5 kg of rice and 3 kg of beans: heavier?
Rice.
Question 3. Difference 5 − 3?
2 kg.
Independent practice
Level 1: Start
- 2 kg in grams
- Which unit for a bag of rice?
- Which unit for a pencil?
- Heavier: 4 kg or 400 g?
- 500 g + 500 g = ? kg
Level 2: Grow
- 4 kg = ___ g.
- Heavier: 600 g or 6 kg?
- 1 kg − 500 g = ___.
Level 3: Stretch
- 3 kg of beans and 2 kg of rice. What is the total mass?
- 1,500 g is how many kg and g?
- Ali says 1 kg is 100 g. What is wrong?
Answers are in the answer key below. Try first, then check.
6. Apply: everyday mathematics
Rice is 5 kg and beans 3 kg. How much heavier is the rice?
Show a sample answer
2 kg.
Another one. A bag of flour is 2 kg. Ama uses 750 g. How many grams are left?
Show a sample answer
2,000 − 750 = 1,250 g
7. Common mistakes
Fix: Compare the mass on a balance.
Fix: 1 kg = 1,000 g.
Fix: Change to the same unit.
8. Lesson summary and revision card
- I can say that mass tells how heavy something is.
- I can use kilograms and grams.
- I can compare the mass of two objects.
- I can change kilograms to grams.
9. Check and master
Answer all 14 questions. You will see feedback after each one.
Your result appears here after you answer every question.
10. Key takeaways
- Mass tells how heavy.
- 1 kg = 1,000 g.
- Use a balance to compare.
11. Next lesson
Next lesson: Capacity. Keep going with the next idea in this course.
Exam practice
These questions are written in the style of common school and international primary assessments. Try them on your own, without looking back. Then check your answers in the marking guide. The marks are shown in brackets.
- How many grams are in 1 kg? [1 mark]
- Change 4 kg to grams. [1 mark]
- Which is heavier, 5 kg or 500 g? Explain. [2 marks]
- A bag has 2 kg of rice and 3 kg of beans. What is the total mass? [2 marks]
- Ben says 1 kg = 100 g. Is he right? Explain. [3 marks]
Total: 9 marks.
Marking guide and model answers
- 1,000 [1]
- 4,000 g [1]
- 5 kg [1]; 5 kg = 5,000 g [1]
- 2 + 3 [1] = 5 kg [1]
- No [1]. 1 kg = 1,000 g [1]. 100 g is a tenth of a kilogram [1].
Score guide: 8 to 9 = secure. 6 to 7 = nearly there, revise the parts you missed. Under 6 = work through the lesson again with a grown-up.
Printable worksheet
- 2 kg in grams
- Unit for a bag of rice
- Unit for a pencil
- Heavier: 4 kg or 400 g?
- 500 g + 500 g in kg
- A heavy bag of rice is measured in ___.
- 1 kg = ___ g.
- 2 kg = ___ g.
- 5 kg − 3 kg = ___.
- 500 g + 500 g = ___.
Homework
Compare the mass of three things at home by holding them. Order them.
Answer key and marking scheme
| Question | Expected response | Marks |
|---|---|---|
| 2 kg in grams | 2,000 g | 2 |
| Unit for a bag of rice | kg | 2 |
| Unit for a pencil | g | 2 |
| Heavier: 4 kg or 400 g? | 4 kg | 2 |
| 500 g + 500 g in kg | 1 kg | 2 |
| Total | 10 |
Practice answers: Worksheet: 1 2,000 g; 2 kg; 3 g; 4 4 kg; 5 1 kg.
Quiz answers: 1 A, 2 B, 3 C, 4 A, 5 B, 6 A, 7 B, 8 C, 9 A, 10 B, 11 C, 12 A, Challenge 1 C, Challenge 2 C.
Extra worksheet answers (items 6 onward): 6 kilograms; 7 1,000; 8 2,000; 9 2 kg; 10 1 kg.
Independent practice answers. Level 1: 1 2,000 g; 2 kilogram; 3 gram; 4 4 kg; 5 1 kg. Level 2: 1 4,000; 2 6 kg; 3 500 g. Level 3: 1 5 kg; 2 1 kg 500 g; 3 1 kg = 1,000 g..
Mastery and remediation
| Objective | Bronze (Developing) | Silver (Proficient) | Gold (Advanced) |
|---|---|---|---|
| O1 Say that mass tells how heavy something is | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O2 Use kilograms and grams | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O3 Compare the mass of two objects | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O4 Change kilograms to grams | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
Courseversity badge thresholds (overall quiz score): Gold = 90–100%; Silver = 80–89.9%; Bronze = 70–79.9%. A badge is never a full record of progress.
If a learner struggles
- Find the misconception: Thinking a bigger object is always heavier. Compare the mass on a balance.
- Explain another way: use real objects first, then pictures.
- Show a simpler example: Hold two objects and say which feels heavier.
- Guided practice: work through one example together and let the learner try the next one.
- Reassess: use the quiz again or the worksheet.
- Move on when the learner shows Silver-level evidence independently.
For parents and guardians
In this lesson your child learns about mass and the units gram and kilogram. You do not need to be good at mathematics to help.
- Weigh food with kitchen scales.
- Ask: which is heavier, a 1 kg bag or a 500 g bag?
- Use the words gram and kilogram while cooking.
- Ask “how do you know?” after each answer, and listen.
- Praise effort, not only right answers. Mistakes are how we learn.
- Ten to fifteen minutes a day is better than one long session.
Teacher package
1–5. Objectives, prerequisites, materials, preparation, duration
Lesson objectives. Learners will: say that mass tells how heavy something is; use kilograms and grams; compare the mass of two objects; change kilograms to grams.
Prerequisite knowledge. Lessons 1 to 3.
Materials. Counters (stones, seeds or bottle tops), paper, pencils, board or chalkboard. Low-resource options: use stones, seeds, sticks, bottle tops or drawings in the sand or on the board instead of printed materials.
Preparation. Gather the counters and draw the example pictures on the board before the lesson.
Suggested duration. 45–60 minutes. It can be split into two shorter sessions.
6–9. Teaching procedure, explanation notes, guided and independent activities
Introduction (5 min). Start with the Discover situation and let learners suggest ideas before you teach.
Explanation (10 min). Teach the Understand section with real objects first, then pictures, then symbols and words.
Guided activity (10 min). You need a balance or a hanger and two bags. Learners follow the Explore steps in pairs.
Independent activity (10 min). Learners complete the independent practice and the worksheet.
Assessment and reflection (5 min). Ask each learner to say one thing they learned and how they know it.
Key questions. Is it heavy or light? Which unit? How many grams in a kilogram?
Teacher explanation notes. Use the concrete, pictorial, abstract order: real objects first, then pictures, then symbols and words. Return to real objects whenever a learner needs support.
10–12. Differentiation, formative assessment, common misconceptions
Support. Use real objects and work with a partner; say each step aloud together. Extension. Ask learners to make up their own example and explain it to a partner.
Formative assessment. Listen to learner explanations, ask “how do you know?”, and check the independent work.
Misconceptions. Thinking a bigger object is always heavier. Compare the mass on a balance.
13–15. Assessment questions, answer keys, marking scheme
Use the quiz and worksheet on this page. The 9-mark exam practice scheme, the 10-mark scheme and all answers are in the answer sections above. Re-check every answer and the marking scheme before publication.
16–19. Remediation, enrichment, homework, teacher reflection
Remediation. Hold two objects and say which feels heavier. Enrichment. Invite learners to find or create three more examples at home or in the classroom and explain them. Homework. See above.
Teacher reflection. After teaching, record: which concepts learners understood; which misconceptions occurred; which activities worked; which learners need more practice; and what to improve next time.
Sources and standards
This lesson is based on the sources below, and no official endorsement is claimed. Reference starting points named in the Courseversity standard: Common Core State Standards for Mathematics, Cambridge Primary and the IB Primary Years Programme. Where a standard code is named, it points to the official framework.
Official standards for this topic area. Common Core State Standards for Mathematics (official site): Grade 2 » Measurement & Data. These pages list the standards that cover this topic area; read them alongside the lesson.
Research used to shape this lesson. Cambridge Primary Mathematics Stage 2 (mass); Common Core 3.MD.A.2 (mass). These sources informed the lesson.