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Weight before and after

EnglishGrade 5ScienceFree

Follow every part of a measured system through mixing and changes of form.

What it is about

Interpret measurements showing conservation in a closed system during mixing/change.

Grade 5 · 10–11 years · 30 challenges

Before you begin

  • Grade4 energy transfer, structures, waves and Earth processes.

What the class will do

  1. Choose and explain · 30 challenges

    Weight before and after

    Interpret measurements showing conservation in a closed system during mixing/change.

Using it in class

Everyone proposes a claim and cites a record before the rotating representative acts. All cases are supplied teaching records, not instructions to conduct experiments. Discuss uncertainty and system boundaries. Full bank: 30–45 minutes.

Give everyone time to think and discuss before one pupil acts at the board. The class explains and confirms together; hints and explanations stay until you move on.

Use an up-to-date browser on a computer connected to a whiteboard or shared display. Touch, mouse and keyboard; optional audio and reduced motion. No pupil accounts or personal devices.

Choose from 5 challenges up to the full activity. Discussion determines the duration: you set the pace.

A look inside the activities

Choose and explain

A closed jar total reads 145 g before salt dissolves. Nothing enters (0 g) or leaves (0 g). What total is predicted afterward (g)?

  • 130
  • 145
  • 160
Explanation and discussion

Dissolving changes visibility and distribution, not the total matter of this closed system. The predicted reading stays 145 g, including its unchanged container.

Why would weighing only the visible salt grains answer a different question?

Choose and explain

A jar is weighed with its dry outside before a test, but with extra water on the outside afterward. What problem appears?

  • Additional outside matter is included only in the second weighing
  • The contents must have created that water from nothing
  • A wet surface prevents any weight measurement in principle
Explanation and discussion

The second measurement includes extra external water. That changes the measured system and can hide whether its original contents were conserved.

What consistent preparation would make the comparison clearer?

Choose and explain

Which report best explains equal total readings after a closed mixing change?

  • No substance could change because every total stayed equal
  • The scale proves every particle’s exact size and shape
  • All included matter stayed within the boundary despite changed appearance
Explanation and discussion

Equal whole-system readings support conservation. They do not forbid new substances or reveal every unseen detail. A good report names its measurement and boundary.

What remaining question would require a property test instead?

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