Primary 4 · Science · Science inquiry
Measuring and recording results
Students use rulers, timers and scales accurately, repeat measurements and present results in tables and column graphs.
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These lessons were written around Australian Curriculum strands and matched to Singapore levels by age (Primary 1 is the first year of primary school). They are not aligned to MOE syllabuses or the PSLE, so check them against the syllabus your child is working towards.
Learning goals
Learners will
- Measure length, time and mass accurately with rulers, timers and scales.
- Repeat measurements and choose a typical result.
- Present results in a clear table and column graph.
Success looks like
- I can measure from the zero mark and write the unit.
- I can repeat a measurement three times and choose the middle value.
- I can draw a results table and a column graph with a title, labels and an even scale.
The big idea
Scientists need accurate measurements so they can trust and share their results.
- Rulers and tape measures measure length. Line up the object with the zero mark, not the end of the ruler. Look straight down at the mark. Write the unit: mm, cm or m.
- Timers measure time in seconds (s) and minutes (min). Start and stop the timer at exactly the moment the event starts and ends.
- Scales measure mass in grams (g) and kilograms (kg); 1 kg = 1000 g. Check the scales read 0 before you start. If you use a bowl, press the zero (tare) button with the bowl on, or subtract the bowl's mass.
Measurements are never perfect. Hands, eyes and timers vary a little. So scientists repeat each measurement, often three times.
If the three results are close, choose the middle value as the typical result. If one result is very different from the others, check for a mistake and measure again.
Record results in a table. Give each column a heading with its unit, such as 'Time (s)'. Write numbers, not words.
Show results in a column graph to compare them. A good column graph has a title, labelled axes with units, an even scale starting at zero, and columns of equal width with gaps between them.
Worked examples
Reading a ruler
A crayon's end lines up with the 2 cm mark and its tip with the 11 cm mark. How long is it?
- The crayon does not start at zero, so subtract the start from the end.
- 11 − 2 = 9.
Answer: 9 cm. (It is easier to line up with zero next time.)
Repeat and choose
A paper helicopter took 2.4 s, 2.6 s and 2.5 s to fall. What is the typical time?
- Put the results in order: 2.4, 2.5, 2.6.
- They are close together, so the results are reliable.
- The middle value is 2.5.
Answer: 2.5 seconds.
Using scales with a bowl
An empty bowl has a mass of 200 g. With rice in it, the scales read 650 g. What is the mass of the rice?
- Subtract the bowl: 650 − 200 = 450.
- Or put the empty bowl on, press tare to read 0, then add the rice.
Answer: 450 g.
Practice check
Have a go, then check your answers. Each answer comes with an explanation.
Answer guide for parents
Where should you line up an object when measuring with a ruler?
The zero mark — Start at the zero mark, which is often a little way in from the end.
Which unit would you use for the mass of an apple?
Grams — Mass is measured in grams or kilograms.
Why do scientists repeat measurements?
To check their results are reliable — Repeating shows whether results are consistent.
Which graph is best for comparing how far a car rolled on four different surfaces?
A column graph — Column graphs compare amounts for different groups.
Results: 31 cm, 30 cm, 58 cm. What should you do?
Check for a mistake and measure again — 58 cm is very different from the others, so check and repeat.
A leaf starts at the 3 cm mark and ends at the 11 cm mark. How long is it in cm?
8 — 11 − 3 = 8 cm.
Three measurements were 30 cm, 32 cm and 31 cm. What is the middle value in cm?
31 — In order: 30, 31, 32. The middle is 31.
An empty bowl is 150 g. With sand in it, it is 400 g. What is the mass of the sand in grams?
250 — 400 − 150 = 250 g.
Watch out for
- Students often measure from the end of the ruler instead of the zero mark. Check the ruler together before measuring.
- Students may think repeating means the first result was wrong. Repeating is what careful scientists always do.
- Some students draw graph scales with uneven steps (0, 5, 20, 25). The steps must be equal for the columns to be compared fairly.
Tips for parents
- Practise reading a ruler, timer and kitchen scales during everyday tasks such as cooking.
- Give your child a table template with headings and units the first few times.
- Safety: use scissors carefully when making the paper helicopter, and stand on the floor, not a chair, when dropping it.
Go further
- Make paper helicopters with different wing lengths, time each fall three times and graph the middle values.
- Measure the mass of five pieces of fruit and draw a column graph.
- Time how long it takes family members to do 10 star jumps and present the results in a table.
About 45 minutes
You'll need
- A 30 cm ruler and a tape measure
- A stopwatch or a phone timer
- Kitchen scales
- A bowl, a cup of dry rice or sand
- Paper (grid paper if you have it) for a table and graph
- A sheet of paper to make a simple paper helicopter or spinner
Key words
- unit
- A standard amount used for measuring, such as centimetres (cm), seconds (s) or grams (g).
- accurate
- Close to the true value.
- mass
- How much matter is in an object, measured in grams (g) or kilograms (kg).
- repeat
- To do a measurement again to check it.
- axis
- One of the two lines on a graph: the horizontal axis runs across and the vertical axis runs up.
- scale
- The numbers along a graph's axis, going up in equal steps.
Still tricky?
For parents
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