What is the relationship between temperature and density?

• A. As temperature increases, density decreases or vice versa
• B. As temperature increases, density increases
• C. As temperature remains constant, density changes unpredictably
• D. As temperature increases, density becomes negative

Answer: (A)

Density is mass per volume, so when temperature rises, particles gain energy and tend to push apart, causing the material to expand. With more volume and the same mass, density decreases. When temperature drops, the material tends to contract, packing the same mass into a smaller volume, so density increases. This inverse relationship is typical for many substances, and it’s especially strong in gases. There are small exceptions like water around 4°C where density behavior isn’t strictly inverse, but outside that narrow range the general pattern holds: density goes down as temperature goes up, and up as temperature goes down.