Let’s go through each example one by one and decide if it’s a physical change or a chemical change.
Remember:
- A
physical change means the substance looks different, but it’s still the same stuff inside. You can often reverse it (like melting ice back to water).
- A
chemical change means something new is made — like when things burn, rust, or cook. It usually can’t be easily undone.
Now let’s look at each case:
1.
Bread is baked.
When you bake bread, the dough turns into bread — it changes color, texture, and smell. New substances are formed (like from yeast reacting). This is a
chemical change.
2.
Boiling water evaporates.
Water turns from liquid to gas (steam), but it’s still H₂O. If you cool the steam, it becomes water again. No new substance is made. This is a
physical change.
3.
A rock is smashed into pieces.
The rock breaks into smaller rocks, but it’s still the same rock material. Just size changed. This is a
physical change.
4.
An old nail gets rusty.
Rust is a new substance — iron reacts with oxygen and water to make rust (iron oxide). You can’t turn rust back into shiny iron easily. This is a
chemical change.
5.
A frozen treat melts.
Ice cream or popsicle goes from solid to liquid, but it’s still the same flavor and ingredients. Melted ice cream can be refrozen. This is a
physical change.
6.
An egg is cooked.
Raw egg turns into cooked egg — the clear part becomes white and solid. That’s because heat changed the proteins in the egg. You can’t uncook an egg. This is a
chemical change.
Now we sort them:
Physical Changes:
- Boiling water evaporates.
- A rock is smashed into pieces.
- A frozen treat melts.
Chemical Changes:
- Bread is baked.
- An old nail gets rusty.
- An egg is cooked.
Final Answer:
PHYSICAL CHANGES:
- Boiling water evaporates.
- A rock is smashed into pieces.
- A frozen treat melts.
CHEMICAL CHANGES:
- Bread is baked.
- An old nail gets rusty.
- An egg is cooked.
Parent Tip: Review the logic above to help your child master the concept of physical changes of matter worksheet.
