What happens to density when a liquid is heated?

What happens to density when a liquid is heated?

• A. The liquid becomes more dense
• B. The liquid's density becomes zero
• C. The density remains constant
• D. The liquid becomes less dense

Answer: (D)

When a liquid is heated, its density tends to decrease. Density is mass per volume, and heating makes the liquid expand: the molecules move faster and push apart a bit, so the volume increases while the mass stays the same. With a larger volume and the same mass, the density falls. That’s why the liquid becomes less dense as it heats. A small caveat is that water has a unusual behavior near 4°C, where density increases with warming from very cold temperatures, but for most liquids the general trend is expansion and lower density with heating.

When a liquid is heated, its density tends to decrease. Density is mass per volume, and heating makes the liquid expand: the molecules move faster and push apart a bit, so the volume increases while the mass stays the same. With a larger volume and the same mass, the density falls. That’s why the liquid becomes less dense as it heats. A small caveat is that water has a unusual behavior near 4°C, where density increases with warming from very cold temperatures, but for most liquids the general trend is expansion and lower density with heating.