At ________ degree Celsius water attains maximum density.

The correct answer is 4 degree Celsius.

Key Points

• Water attains its maximum density at 4 degrees Celsius.
• At this temperature, water molecules are most closely packed together, making it denser than at any other temperature.
• This property of water is due to the unique hydrogen bonding between water molecules.
• When water is cooled below 4 degrees Celsius, it starts to expand again, which is why ice floats on water.

Additional Information

• Hydrogen Bonding:
  • Hydrogen bonds are weak interactions that occur between the hydrogen atom of one water molecule and the oxygen atom of another.
  • This bonding causes water to have a high boiling point, surface tension, and unique density properties.
• Thermal Expansion of Water:
  • Water expands when it freezes, which is unusual compared to most substances that contract when they solidify.
  • This expansion is due to the formation of a crystalline structure in ice, making it less dense than liquid water.
• Density Anomaly of Water:
  • The density anomaly refers to water being densest at 4 degrees Celsius, rather than at its freezing or boiling points.
  • This anomaly plays a crucial role in aquatic ecosystems, especially in temperate climates where ice forms on the surface of water bodies, insulating the water below.
• Implications for Aquatic Life:
  • The density anomaly of water ensures that ice forms on the surface of lakes and ponds, providing insulation and helping maintain the ecosystem beneath.
  • This property allows aquatic life to survive through the winter even when the surface is frozen.