ACARA v9 CONTENT DESCRIPTION “follow procedures to make and record observations, including making formal measurements using familiar scaled instruments and using digital tools as appropriate”
Builds on earlier looking and counting. Now you follow the steps of a measurement, read a scaled instrument the right way, and write each reading down with its unit so the record can be trusted and compared.
Following the steps of a measurement
A measurement is not a guess. It follows the same steps every time. First you pick the right instrument: a ruler for how long something is, a thermometer for how hot or cold, a measuring jug for how much liquid. Each instrument has a scale, which is a line of marks with numbers. You read the mark the object or the liquid lines up with, and you write down the number and its unit: centimetres, degrees or millilitres. Reading the scale level with your eye, straight on, keeps the number honest.
Read the scale: record a bean plant week by week
Each week a bean plant was measured with a ruler in centimetres. Switch between the table and the chart to see the same recorded readings two ways.
The table holds the exact numbers you read off the ruler each week. The chart turns those same records into a shape, and the steady climb shows the plant growing faster as it grows taller.
Reading a scaled instrument correctly
A scaled instrument only gives the right answer if you read it the right way. On a thermometer, the liquid rises up a tube past a line of numbers. You read the mark at the very top of the liquid, looking straight on, and write the temperature in degrees. On a measuring jug, the liquid settles at a line on the side, and you read that line in millilitres. Reading from above or below the mark makes the number look bigger or smaller than it really is, so you always get level with the scale first.
Record temperatures: a digital tool helps you log readings
A thermometer was read at the same hour for six days and the degrees were logged. The bar chart and the line graph are two ways a digital tool can show your recorded readings.
Each bar is one reading you wrote down in degrees. A digital tool draws the chart for you from the records, but the readings themselves still came from reading the thermometer carefully each day.
Watching for a reading that does not fit
When you record a row of readings that should change smoothly, one number sometimes jumps far away from the rest. That odd reading is worth a second look. Perhaps the ruler slipped, or you read the wrong line, or the jug was tilted. A careful recorder does not rub it out and does not panic. You simply measure that one again, the same careful way, and see whether the strange reading was a slip.
Spot the reading to measure again
Six cups of water were each measured with a measuring jug in millilitres. The amounts should rise steadily, but one reading does not fit the climb.
Click the point that does not fit the pattern of the others.
Which records can you trust?
A measurement is only useful if it was made carefully and written down with its unit. Some records were taken the proper way, reading the scale level and noting the unit. Others were rushed, guessed, or written without a unit, so they cannot be trusted or compared. Sort each one by whether it is a careful, trustworthy record of the measuring you set out to do.
Decide which records were measured carefully
The aim: make careful, trustworthy records of length, temperature and volume. Decide which records meet that aim.
Claim: A good record gives an exact reading from the scale, with the matching unit, taken the careful way.
The pencil was read against the ruler as 14 cm, looking straight on at the mark.
The water in the thermometer reached the 22 line, so 22 degrees C was written down.
The juice was about a glassful, so nothing exact was written in the table.
The jug was filled to the 200 line and 200 mL was recorded next to the unit.
A number was guessed from across the room without reading the scale up close.
Decide whether each statement is evidence for the claim, or not.
Why this matters
Careful measuring and recording is the backbone of every investigation. When you follow the steps, read a scale the right way, and write each reading down with its unit, your records can be checked, compared and trusted by anyone. It is the same care a nurse, a builder or a scientist takes whenever a measurement has to be right.
Quick self-check
1. You measure how long a plant is with a ruler. Which unit do you write down?
2. To read a thermometer correctly, you should look at the top of the liquid...
3. You pour juice into a measuring jug. Where do you read the amount?
4. Why do scientists write each reading down straight away instead of trusting memory?
5. Your recorded lengths are 4 cm, 6 cm, 8 cm, then 30 cm, then 12 cm. What should you do with the 30 cm?