Which solution will decrease in volume when cooled from 25^ext{o}C to 0^ext{o}C at constant pressure?

• A. Pure water
• B. Aqueous NaCl solution
• C. Aqueous glucose solution
• D. Ethanol solution

Answer: (A)

Verified step by step guidance

1. Understand the physical property involved: volume change with temperature at constant pressure is related to the thermal expansion or contraction of the substance.
2. Recall that most liquids contract (decrease in volume) when cooled, but water is a notable exception between 0°C and 4°C, where it actually expands upon cooling due to its hydrogen bonding structure.
3. Analyze pure water: as it cools from 25°C to 0°C, it expands rather than contracts, so its volume increases, not decreases.
4. Consider aqueous solutions (NaCl, glucose) and ethanol: the presence of solutes disrupts the hydrogen bonding network of water, generally causing these solutions to behave more like typical liquids that contract upon cooling.
5. Conclude that among the options, pure water is unique because it increases in volume when cooled near freezing, so the solutions (aqueous NaCl, glucose, ethanol) will decrease in volume when cooled from 25°C to 0°C at constant pressure.