Measuring mass and weight
Measure and begin to record mass/weight using non-standard and standard units
What a learner can do afterwards
- Use a balance to compare masses of two objects
- Measure mass using non-standard units (e.g. 'this book weighs 5 cubes')
- Begin to read a simple scale for mass
1 · Read
Start with an empty equal-arm balance that is level. Put one object in each pan. The heavier side goes down and the lighter side goes up. If the pans stay level, the objects have equal mass.
To measure with cubes, use cubes that all have equal mass. Put the object in one pan. Add cubes to the other until the pans are level. Count every cube and write the number with the unit. A toy balances 8 cubes, so its mass is recorded as 8 cubes.
Compare cube measurements only when the cubes used have equal mass. If one object needs more of those cubes to balance, it has greater mass. A bead balances 1 cube and a toy balances 4 of the same cubes. The toy has greater mass.
Grams are written g. Before weighing, set the empty scale to zero and check its unit. Wait for the reading to stop changing. A mass record needs a number and a unit. Count every measuring cube, whatever its colour. Use equal-mass cubes for comparisons; size alone does not tell mass. Replacing an object with another of the same mass keeps the balance result unchanged.
Choose what you want to weigh. Weighing a cup alone measures the cup. Weighing the cup and its box together measures both objects, not just the cup. Putting the cup in the box does not change the cup's own mass. To record the cup's mass, weigh it alone. To record a closed box's mass, include all its parts.
Compare scale readings only when they use the same unit. The larger reading means greater mass. If two toys read 4 g and 7 g, the 7 g toy is heavier. On a scale with steps of 1 g, the number after 5 is 6, then 7.
A balance shows what is heavier. A scale gives you a number for the weight.
Original readings, questions and flashcards written for this topic.
2 · Watch
Take it off screen
Where it sits
Learn first
This opens up
Where this leads
17 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.