Mass 1
Outcomes
A student:

 MA11WM
describes mathematical situations and methods using everyday and some mathematical language, actions, materials, diagrams and symbols

 MA112MG
measures, records, compares and estimates the masses of objects using uniform informal units
Content
 Students:
 Investigate mass using a pan balance
 identify materials that are light or heavy
 place objects on either side of a pan balance to obtain a level balance
 use a pan balance to compare the masses of two objects
 discuss the action of a pan balance when a heavy object is placed in one pan and a lighter object in the other pan (Communicating)
 predict the action of a pan balance before placing particular objects in each pan (Reasoning)
 sort objects on the basis of their mass
 use a pan balance to find two collections of objects that have the same mass, eg a collection of blocks and a collection of counters
 use drawings to record findings from using a pan balance
Background Information
Mass is an intrinsic property of an object, but its most common measure is in terms of weight. Weight is a force that changes with gravity, while mass remains constant.
Language
Students should be able to communicate using the following language: mass, heavy, heavier, light, lighter, about the same as, pan balance, (level) balance.
As the terms 'weigh' and 'weight' are common in everyday usage, they can be accepted in student language should they arise.
National Numeracy Learning Progression links to this Mathematics outcome
When working towards the outcome MA1‑12MG the subelements (and levels) of Understanding units of measurement (UuM2) describe observable behaviours that can aid teachers in making evidencebased decisions about student development and future learning.
The progression subelements and indicators can be viewed by accessing the National Numeracy Learning Progression.
Mass 2
Outcomes
A student:

 MA11WM
describes mathematical situations and methods using everyday and some mathematical language, actions, materials, diagrams and symbols

 MA12WM
uses objects, diagrams and technology to explore mathematical problems

 MA13WM
supports conclusions by explaining or demonstrating how answers were obtained

 MA112MG
measures, records, compares and estimates the masses of objects using uniform informal units
Content
 Students:
 Compare the masses of objects using balance scales (ACMMG038)
 compare and order the masses of two or more objects by hefting and check using a pan balance
 recognise that mass is conserved, eg the mass of a lump of plasticine remains constant regardless of the shape it is moulded into or whether it is divided up into smaller pieces
 use uniform informal units to measure the mass of an object by counting the number of units needed to obtain a level balance on a pan balance
 select an appropriate uniform informal unit to measure the mass of an object and justify the choice (Problem Solving)
 explain the relationship between the mass of a unit and the number of units needed, eg more toothpicks than pop sticks will be needed to balance the object (Communicating, Reasoning)
 record masses by referring to the number and type of uniform informal unit used
 compare two or more objects according to their masses using appropriate uniform informal units
 record comparisons of mass informally using drawings, numerals and words, and by referring to the uniform informal units used
 find differences in mass by measuring and comparing, eg 'The pencil has a mass equal to three blocks and a pair of plastic scissors has a mass of six blocks, so the scissors are three blocks heavier than the pencil'
 predict whether the number of units will be more or less when a different unit is used, eg 'I will need more pop sticks than blocks as the pop sticks are lighter than the blocks' (Reasoning)
 solve problems involving mass (Problem Solving)
 estimate mass by referring to the number and type of uniform informal unit used and check by measuring
Background Information
In Stage 1, measuring mass using informal units enables students to develop some key understandings of measurement. These include: repeatedly using a unit as a measuring device; selecting an appropriate unit for a specific task; appreciating that a common informal unit is necessary for comparing the masses of objects; understanding that some units are unsatisfactory because they are not uniform, eg pebbles.
Students should appreciate that the pan balance has two functions: comparing the masses of two objects and measuring the mass of an object by using a unit repeatedly as a measuring device.
When students realise that changing the shape of an object does not alter its mass, they are said to conserve the property of mass.
Language
Students should be able to communicate using the following language: mass, heavier, lighter, about the same as, pan balance, (level) balance, measure, estimate.
'Hefting' is testing the weight of an object by lifting and balancing it. Where possible, students can compare the weights of two objects by using their bodies to balance each object, eg holding one object in each hand.
Refer also to language in Mass 1.
National Numeracy Learning Progression links to this Mathematics outcome
When working towards the outcome MA1‑12MG the subelements (and levels) of Understanding units of measurement (UuM2UuM6) describe observable behaviours that can aid teachers in making evidencebased decisions about student development and future learning.
The progression subelements and indicators can be viewed by accessing the National Numeracy Learning Progression.