Lesson 7 of 19
Five signs, and what each one is worth
Show on a big screenLemon juice and baking soda foam over the rim. Is something new made?
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The idea
Yes. The foam is carbon dioxide, a new gas.
- A colour changes. Grey iron turns orange.
- A gas comes off. Bubbles rise where there were none.
- Heat or light is given out or taken in.
- A smell appears.
- A solid appears in a liquid.
The rule
A sign is only a clue. Ask if the stuff at the end is new.
Each sign also happens in changes that make nothing new.
| The sign | New substance | No new substance |
|---|---|---|
| Colour changes | An iron gate turns orange | Wet sand looks darker |
| A gas comes off | Lemon juice fizzes with baking soda | A hot pan gives off steam |
| Heat or light | Paper burns | Ice takes heat from a drink |
| A smell | Milk turns sour | Perfume scents a room |
| A solid appears | Lime water turns milky | Sea water dries and leaves salt |
Try the lab to finish this lesson.