## Does Water Expand or Contract When Heated?
The answer to this question depends on the temperature range being considered.
Below 4°C (39.2°F)
When water is heated below 4°C, it contracts. This is an unusual property of water and is one of the reasons why ice floats. As water is heated from 0°C to 4°C, the water molecules become more tightly packed, causing the water to become denser and more compact. This is why ice floats on top of liquid water.
Above 4°C (39.2°F)
When water is heated above 4°C, it expands. This is the more typical behavior of matter when heated. As water is heated above 4°C, the water molecules gain energy and move around more vigorously, causing the water to expand. This is why water boils at 100°C (212°F) – the water molecules have gained enough energy to overcome the intermolecular forces holding them together and turn into a gas.
Density of Water vs Temperature
The following graph shows the density of water as a function of temperature:
[Image of a graph showing the density of water vs temperature]
As you can see from the graph, the density of water is highest at 4°C and decreases as the temperature increases or decreases from this point.
Applications of Water’s Unusual Expansion Behavior
The unusual expansion behavior of water below 4°C has several important applications:
Ice floats on water. This is why icebergs float in the ocean and why frozen lakes don’t sink.
Water pipes can burst in winter. If water pipes are not properly insulated, the water inside can freeze and expand, causing the pipes to burst.
Fish can survive in winter. The water in lakes and ponds freezes from the top down, but the water near the bottom remains liquid because it is denser than the ice. This allows fish to survive in winter by swimming in the liquid water near the bottom of the lake or pond.
Conclusion
Water is a unique substance with many interesting properties. One of these properties is its unusual expansion behavior below 4°C. This behavior has several important applications, including the ability of ice to float on water and the ability of fish to survive in winter.