ScienceGrade 9ages 14–15
🫧 A new substance
Ice and liquid water look completely different, yet they share every material property — while rust looks only a little different from iron but is, in fact, an entirely new substance, which is why looks alone can't tell you what kind of change happened.
Try this lesson freeNo card needed. The first lesson is free.
Download on the App StoreWhat your child learns
- The question is not whether something looks different. The question is whether the properties changed.
- Ice and water look very different, and still they have the same material properties.
- Rust is nothing like iron: it is brittle, reddish, and not drawn to a magnet as clean iron is.
- A second test is reversibility: ice comes back on freezing, and rust does not come back as iron.
The mistake most kids make here
Melting is a chemical change, and rust is only dirt on the same iron.
Try one question
A chemical change…
Chemical
- only melts ice into the same water
- makes a new substance
- only paints with no substance
Answer
makes a new substance — Yes. And new means having different properties, not merely a different look.
How Maya teaches it
Your child tells Maya what they did in class. She teaches this topic at her desk, asks questions with tappable answers, and when the answer is wrong she explains why that answer was tempting instead of saying “try again”. She remembers what did not land and comes back to it.
Your child has it when they can: Say when a new substance is made, and why melting is not that.
How to help at home
The real question isn't whether something looks different afterward — it's whether the properties changed. Melting ice looks dramatically different (solid to liquid) but the water has all the same material properties as the ice did.
Rust, on the other hand, is brittle, reddish, and doesn't get pulled to a magnet the way clean iron does — even though it can look like iron just got a bit dirty. Those different properties are the sign that a new substance formed.
A second test your child can use is reversibility: freeze the water and you get ice back, unchanged. But there's no simple way to turn rust back into iron — once the reaction happens, the original substance is gone.
A good sign they've got it: they can name the two tests (did the properties actually change, and can the original be recovered) and use them to sort melting (physical) from rusting (chemical), instead of judging by how different something looks.
Questions parents ask
- Why isn't melting ice a chemical change, even though it looks so different?
- The water that results has exactly the same material properties as the ice — same substance, just a different state. A chemical change requires the properties themselves to change, which melting doesn't do.
- Why is rust a chemical change if it still looks mostly like iron?
- Rust is brittle, reddish, and isn't attracted to a magnet the way iron is — its properties are genuinely different from iron's. That's the sign a new substance formed, even though the visual change is subtle.
- Is there a simple test to tell physical and chemical changes apart?
- Two tests help: check whether the material's actual properties changed (not just its appearance), and check whether the original substance can be recovered easily. Ice recovers on freezing; rust doesn't recover as iron.
- How does Maya teach this differently from a list of examples?
- Maya asks what a chemical change actually does, with real options, so the child reasons through properties and reversibility instead of memorizing a list of 'physical' and 'chemical' examples by heart.
No card needed. The first lesson is free.
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Sources: Next Generation Science Standards