Why does the density of a liquid decrease as its temperature increases?

• A. Because the mass of the liquid decreases as temperature increases.
• B. Because the liquid expands, increasing its volume while the mass remains constant.
• C. Because the liquid gains more particles at higher temperatures, increasing its density.
• D. Because the liquid contracts, decreasing its volume at higher temperatures.

Answer: (B)

Verified step by step guidance

1. Recall the definition of density, which is given by the formula \(\text{density} = \frac{\text{mass}}{\text{volume}}\).
2. Understand that when temperature increases, the mass of the liquid remains constant because no particles are added or removed.
3. Recognize that increasing temperature causes the liquid to expand, meaning its volume increases.
4. Since the volume increases while the mass stays the same, the overall density decreases because the same mass is spread over a larger volume.
5. Conclude that the decrease in density with increasing temperature is due to thermal expansion of the liquid, not a change in mass.