A metallic sphere is heated from 27°C to 200°C Without change of state. Which of the following  changes would have resulted from the heating?

Step 1: Analyze the question A metal sphere is heated from 27°C to 200°C and stays solid. We need to find what happens to its volume and density.

Step 2: The concept Most solids undergo thermal expansion when heated. The atoms vibrate more strongly and move slightly farther apart, so the volume increases.

The volume expansion formula is:

ΔV = V₀ γ Δθ

where γ is the coefficient of volume expansivity and Δθ is the temperature change.

Density is given by:

ρ = mass / volume

Step 3: Apply it

• Temperature rises by Δθ = 200 − 27 = 173°C, so the volume increases.
• The mass stays the same, because no matter is added or removed.
• Since ρ = m/V, a larger V with a constant m gives a smaller density.

Step 4: Check the options

• A. Wrong, because the volume does change.
• B. Wrong, because the density cannot increase when the volume increases and the mass is constant.
• C. Correct: the volume increases and the density decreases.
• D. Wrong, because if the volume changes, the density must change too.

Step 5: Exam tip Remember: "Heat it up, volume goes up, density goes down" (mass stays the same). In WASSCE and JAMB questions on expansion, always ask yourself whether the mass changes. If it does not, density moves in the opposite direction to volume.