Reversible Changes
Demonstrate that dissolving, mixing, and changes of state are reversible changes where no new materials are formed
What a learner can do afterwards
- Define a reversible change as one where the original materials can be recovered
- Give at least three examples of reversible changes: melting, freezing, dissolving, evaporating
- Explain how to reverse each example (e.g. freeze melted chocolate, evaporate a solution)
The lesson
A reversible change is a change you can undo. Melt chocolate, then freeze it again, and you get chocolate back. Dissolve sugar in water, then let the water evaporate, and the sugar is still there. No new material forms. You get back exactly what you started with.
Mia leaves a chocolate bar in the sun and it melts into a puddle. She puts the puddle in the freezer. An hour later, it is solid chocolate again, the same chocolate she started with.
A change is reversible if you can get back the exact same material. If a change makes something completely new, it is not reversible.
Melting, freezing, dissolving, and evaporating are reversible changes: you always get the original material back, and no new material forms.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 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.