Question

When a metal bar is cooled, then which one of these statements is correct :

• A. Length, density and mass remain same
• B. Length decreases, density increases but mass remains the same
• C. Length and mass decrease but density remains the same
• D. Length and density decrease but mass remains the same

Answer 1

The correct option is B Length decreases, density increases but mass remains the same

When a metal bar is cooled, the spacing between molecules decreases, their vibrations decrease, the attraction among them increases and they come closer. But the quantity of matter in it doesn't change. Hence the length decreases, mass per unit volume i.e. density increases and mass remains unchanged.