Simulic
English

Physical and chemical changes – evidence bench

ChemistryReactions & RedoxAges 13–14

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A virtual test bench with seven changes: melting ice, dissolving salt, boiling water, burning steel wool, rusting iron, baking soda with vinegar and precipitating copper(II) hydroxide. Weigh before and after in an open or sealed container, measure the temperature, look for evidence (gas, colour change, precipitate, energy change, new substance), compare properties before and after, and use a particle view that shows whether bonds break, then classify each change as physical or chemical in a results table.

Lesson: Physical and chemical changes; evidence of chemical reactions; conservation of mass

What it shows

In a physical change, such as melting, dissolving or boiling, the particles stay the same and only their arrangement or spacing changes, so no new substance forms and the change is usually easy to reverse. In a chemical change, bonds break and atoms rearrange into new substances with different properties. Clues include a gas, a colour change, a precipitate and an energy change, but only a new substance is decisive: boiling also makes bubbles, and dissolving can cool the water. Mass is conserved in every change; it only seems to change in an open container when a gas escapes or joins from the air.

How to use

Pick a change and choose Open to the air or Sealed (closed system), press Weigh before, then Start and watch the balance, the thermometer and the particle view. Press Weigh after, tick the evidence you saw and press Check evidence, then choose Physical change or Chemical change. Use Test properties and Try to reverse to collect more evidence, and Record result to fill the table.

Parameters you can change

  • Change Melting ice, Dissolving salt in water, Boiling water, Burning steel wool (iron) in air, Rusting iron nails (7 days), Baking soda (NaHCO₃) with vinegar, Copper(II) sulfate with sodium hydroxide (precipitate)
  • Container Open to the air (gases can enter and leave), Sealed flask (closed system)
  • Show the particle view
  • Show the answers as soon as the change ends (teacher demo)

Questions to explore

  1. Why does burning steel wool in air increase the mass, while baking soda and vinegar in an open beaker decrease it?
  2. Boiling water also makes bubbles; why is boiling still a physical change?
  3. How could you show that mass is conserved in every change?

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