When the temperature of a product is increased, the material will expand and the density will ____________.

• A. Increase
• B. Decrease
• C. Remain constant
• D. Fluctuate

Answer: (B)

When temperature goes up, most materials expand because their particles move more and take up more space. Density is mass per unit volume, so if the mass stays the same but the volume increases, the density must drop. This is true for solids and liquids as they heat, and even more pronounced for gases because their volume changes are much larger with temperature. So increasing temperature leads to a decrease in density.

The other possibilities don’t fit the usual behavior: density increasing would imply the material shrinks as it’s heated, which doesn’t happen; remaining constant would ignore the expansion; fluctuating isn’t the typical predictable outcome of heating a material.