What a new substance means
A teacher heats magnesium ribbon, a thin strip of metal. The ribbon burns to a white powder.
Step 1 of 3
- The ribbon: grey, shiny, bends easily.
- A teacher holds it near a flame. It burns with a bright white flame.
- A white powder is left. It does not bend or burn again.
Read each change. Did a new substance form?
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The rule
A chemical reaction makes a new substance with new properties. The starting substances are reactants. The new substances are products.
The white powder is not ribbon in another shape. Ribbon bends and burns. The powder crumbles and will not burn again.
A new colour or a new gas may show a reaction. So can a change in temperature.
A gas alone is not proof. Boiling water gives steam, and steam is still water.
| The change | Before | After | A property only the product has |
|---|---|---|---|
| Magnesium ribbon burns | grey, bends, burns | white powder | crumbles, will not burn |
| Sugar stirred into water | white grains | clear sweet liquid | none. It still tastes sweet. |
A reactant is not gone. Its atoms are still there, inside the product, in new groups.