Discuss how the objects could be ordered from lightest to heaviest. Ask the students to consider how they could check if the feather is lighter than the tissue, or if the rock is heavier than the barbell.
Choose two objects from around the classroom that can fit into/onto a set of balance scales. Show the objects to the students and ask them which one they think is heavier. Lead them to the idea of using the balance scales to check.
Demonstrate how to compare the masses by putting the objects into/onto the balance scales. Confirm which object is heavier/lighter and explain how you could tell e.g. the heavier object pulls the balance scales down on one side, making it hang lower than the other side.
Allow the students to collect five different objects from around the classroom and take them back to their desks. If using the constructed balance scales from Lesson 2, have the students work in pairs so that they can hold each other’s scales when comparing.
Encourage the students to compare the masses of the objects using their balance scales, then arrange them in order from the lightest to the heaviest. Ask the students to write/draw the list into their workbooks. If the students are having trouble discerning a difference between two objects, ask them to replace one of the objects with something heavier/lighter so they can make an ordered list.
Ask the students to share their comparisons with three other classmates. Encourage them to describe how they could tell the differences in masses and allow them to give a demonstration using their scales.
Gather together as a class. Review the task, revise the key vocabulary and check for any misconceptions.
Encourage more capable students to look for objects around the classroom that have the same mass.
Assist less confident students as they are selecting classroom objects to compare.
Suggested Assessment Strategies
used strategic whole class or individual questioning
observed student participation during learning activities