Which of the following expands when the temperature is lowered? Equal volumes of
Select one: A. wood. B. iron. C. water at 4 degrees C. D. helium. E. None expands when the temperature is lowered.
The correct answer and explanation is:
The correct answer is C. water at 4 degrees C.
Water is unique in its behavior when cooled. Most substances contract (decrease in volume) as they are cooled, but water behaves differently. As water cools, it contracts, but once it reaches around 4°C, it begins to expand again as it cools further. This phenomenon occurs because of the hydrogen bonding in water molecules.
At temperatures above 4°C, water molecules move more rapidly and are able to stay closer together, causing water to contract. However, when the temperature drops below 4°C, the molecules begin to arrange themselves into a crystalline structure, which takes up more space. This arrangement forms what is known as ice, which is less dense than liquid water. Therefore, water at 4°C is at its densest, and cooling it further causes it to expand.
This property of water is essential for life on Earth. If water did not expand upon freezing, ice would sink rather than float. This is important for aquatic life, as ice floating on the surface of lakes and rivers insulates the water below, keeping it warmer and allowing organisms to survive in colder temperatures.
Other substances, such as wood, iron, and helium, follow the typical pattern where they contract when cooled. Helium, in particular, becomes a liquid only at extremely low temperatures (below -268.93°C), and like most gases, it contracts as it cools. Thus, water at 4°C is the only substance in this list that expands when the temperature is lowered.