The magnitude of the expansion or contraction of a substance depends on the i. temperature change ii. nature…

Analyze the question: We are asked which factors affect how much a substance expands or contracts when heated or cooled.

Concept: For linear expansion:

ΔL = α · L₀ · Δθ

• α is the linear expansivity, which depends on the nature (material) of the substance (e.g. copper, iron, glass all differ).
• L₀ is the original length, which relates to the size of the substance. A longer rod expands more than a shorter one of the same material for the same temperature rise.
• Δθ is the temperature change. A bigger change gives a bigger expansion.

The same idea applies to area expansion (ΔA = βA₀Δθ) and volume expansion (ΔV = γV₀Δθ).

Check each statement:

• i. Temperature change: correct, since ΔL is proportional to Δθ.
• ii. Nature of the substance: correct, since α differs from material to material.
• iii. Size of the substance: correct, since ΔL is proportional to the original length (or area or volume).

All three are correct.

Answer: D. i, ii and iii

Tip: Remember the formula ΔL = αL₀Δθ. Every symbol on the right-hand side is a factor that affects the expansion: the material (α), the original size (L₀), and the temperature change (Δθ). If a question asks what the expansion depends on, check it against this formula.