Question

1. classify the following changes as physical or chemical.

a. boiling
b. crumpling
c. burning
d. freezing
e. evaporating
f. rotting
g. rusting
h. sawing
i. crushing

1. list evidence that a chemical change has occurred.

Explanation:

For Question 9:

Physical changes alter form but not chemical composition; chemical changes create new substances.

• Boiling: Only changes water's state, no new substance.
• Crumpling: Only changes paper's shape, no new substance.
• Burning: Creates ash/gas, new substances form.
• Freezing: Only changes water's state, no new substance.
• Evaporating: Only changes liquid to gas, no new substance.
• Rotting: Breaks matter into new organic compounds.
• Rusting: Iron reacts with oxygen to form iron oxide (new substance).
• Sawing: Only changes wood's size/shape, no new substance.
• Crushing: Only changes material's size/shape, no new substance.

Chemical changes produce distinct, measurable signs that a new substance has formed. These are the key observable evidences.

Answer:

a. Boiling: Physical change
b. Crumpling: Physical change
c. Burning: Chemical change
d. Freezing: Physical change
e. Evaporating: Physical change
f. Rotting: Chemical change
g. Rusting: Chemical change
h. Sawing: Physical change
i. Crushing: Physical change

---

For Question 10: