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Technologies K–10 · Years 1–2

Inside a digital kitchen scale: input, processing and output

Digital Technologies (NSW Science and Technology K–6, 2017); Digital Technologies: Knowledge and understanding, Digital systems (ACARA v9)

PracticalLow risk

The idea

A digital kitchen scale is a digital system: a sensor feels the load (input), a chip turns it into a number (processing) and the display shows grams (output).

What you need

  • 1 digital kitchen scale reading to 1 g
  • 1 plastic cup
  • 1 measuring jug marked at 250 mL
  • Tap water
  • 3 classroom objects to weigh: a glue stick, an apple, a pencil case
  • Recording sheet with columns: input, processing, output

How to do it

  1. Name the parts you can see: the platform and buttons (inputs) and the display (output). Talk about the hidden part that turns the push on the platform into a number.
  2. Switch the scale on with nothing on the platform and read the display.
  3. Put the empty cup on the platform, then press the tare (zero) button and read the display again.
  4. Fill the jug exactly to the 250 mL line, pour the water into the cup and read the display.
  5. Weigh the three objects and record each reading.
  6. Fill in the recording sheet: what went in, what the scale did, what came out.

What you should see

With nothing on the platform the display reads 0 g. After tare, the display returns to 0 g although the cup is still there, because the scale stores the cup's reading and subtracts it. 250 mL of water at 20 °C has a mass of 249.55 g, which rounds to 250 g, so the display reads about 250 g when the jug was filled exactly to the line; a difference of a few grams comes mostly from reading the jug line and from water left in the jug. The learner knows it worked when they can name the input, the processing step (tare subtracting the cup) and the output.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

  • The scale knows what the object is (it only measures how hard the load pushes down).
  • Tare makes the cup weigh nothing (the scale subtracts the cup's reading from the total).
  • Only computers with screens and keyboards are digital systems (a kitchen scale is one too).

Safety card

Low riskLearners carry it out

Hazards

  • Spilled water on the floor or on electrical items

Controls

  • Scale kept on a tray; spills wiped at once; scale battery cover closed

Note

No chemicals or heat. Record the activity on Primary School RiskAssess (riskassess.com.au).

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

  • Science and Technology K–6 Syllabus (2017), NESA. The syllabus taught in 2026; the 2024 syllabus replaces it from 2027. Code read from the official syllabus document (DOCX) on 2026-09-22.ST1-11DI-T
  • Science and Technology K–6 Syllabus (2024), NESA. Implementation from 2027, so this code describes the future syllabus. Code read from the outcomes page on 2026-09-22.ST1-DDT-01
  • Australian Curriculum v9AC9TDI2K01

Sources

The pages the author read to write this activity.

  1. www.nsw.gov.au/education-and-training/nesa/curriculum/science/science-and-technology-k-6-2017
  2. curriculum.nsw.edu.au/learning-areas/science/science-and-technology-k-6-2024/outcomes
  3. www.digitaltechnologieshub.edu.au/plan-and-prepare/scope-and-sequence-f-10/years-1-2/using-digital-systems-safely/common-digital-systems-we-use
  4. www.digitaltechnologieshub.edu.au/media/barlbtay/f-2-hardware-and-software_unit-overview.pdf

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