Differentiate between slow and fast changes.

Changes in nature can broadly be classified into slow and fast changes.

• Slow changes: These take place gradually over a long time. Examples include rusting of iron, growth of a tree, or evolution. They are usually irreversible.
• Fast changes: These occur within seconds or minutes. Examples include burning of paper, lightning, or volcanic eruption.

Key differences:

• Speed: Slow changes take years or centuries, while fast changes are almost instantaneous.
• Examples: Growth of nails (slow), explosion of crackers (fast).
• Impact: Slow changes affect ecosystems gradually, while fast changes often cause immediate impact.

In exams, it's best to write with examples. For instance, cooking rice is a fast change, while fermentation of fruits is relatively slow. Both, however, represent natural chemical/physical processes.