Chemical and Physical Changes Quiz

Grade 7 · Science · Quiz

Test your ability to identify and distinguish physical and chemical changes in matter.

Questions

Rusting iron is an example of which type of change?
1. Physical
2. Chemical
3. Reversible
4. Nuclear
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Answer: Chemical
Rusting is a chemical reaction between iron and oxygen (and water) that forms iron oxide (rust), a completely new substance with different properties.
Melting ice cream is a physical change.
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Answer: True
Melting ice cream changes its state from solid to liquid, but it is still ice cream. No new substance is formed — it can refreeze into a solid again.
The new substances formed during a chemical reaction are called ___.
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Answer: products
In a chemical reaction, reactants are converted into products. The products have different chemical compositions and properties than the reactants.
Which of the following indicates that a chemical change has occurred?
1. A change in size
2. A change in shape
3. Release of heat and light
4. A change in texture
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Answer: Release of heat and light
Heat and light release (like a flame) signals new chemical bonds forming. Size, shape, and texture changes by themselves are physical changes.
Baking a cake is a reversible chemical change.
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Answer: False
Baking causes irreversible chemical reactions (proteins denature, starches change structure). You cannot un-bake a cake back into raw batter.
According to the Law of Conservation of Mass, what happens to matter during a chemical reaction?
1. Some matter is destroyed
2. Matter is created from energy
3. Total mass stays the same
4. Matter always increases
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Answer: Total mass stays the same
The Law of Conservation of Mass states that atoms are neither created nor destroyed in chemical reactions — they just rearrange into new combinations.
A solid that forms from a liquid during a chemical reaction is called a ___.
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Answer: precipitate
A precipitate is a solid that forms when two liquids react. For example, when certain solutions are mixed, a colored solid may suddenly appear and settle out.
Cutting wood into smaller pieces is a chemical change.
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Answer: False
Cutting wood changes its size and shape but does not change what the wood is made of — no new substance is created. This is a physical change.
Which process is a physical change?
1. Burning gasoline
2. Digesting food
3. Boiling water
4. Baking bread
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Answer: Boiling water
Boiling water converts liquid water to water vapor — it is still H₂O in a different state. No new substance is formed, making it a physical change.
When an antacid tablet bubbles in water, what indicates a chemical change?
1. The tablet gets smaller
2. The water becomes cloudy
3. A gas (CO₂) is produced
4. The water temperature drops slightly
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Answer: A gas (CO₂) is produced
The CO₂ gas produced when the antacid reacts with water is a new substance — a sign of a chemical change. The fizzing is produced by CO₂ bubbles escaping.

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