Phase Changes
Understanding states of matter and transitions between them
Topics
How does water boil?
Water boils when its temperature reaches 100°C (212°F) at standard pressure and heat energy is added. Water molecules gain enough energy to overcome liquid bonds and escape as vapor, forming bubbles throughout the liquid.
Read more →How does water freeze?
Water freezes when its temperature drops to 0°C (32°F) and heat energy is removed. Water molecules slow down and form a crystalline structure held together by hydrogen bonds, transitioning from liquid to solid ice.
Read more →What is evaporation?
Evaporation is the process where liquid molecules at the surface gain enough energy to escape into the gas phase. It occurs at any temperature below the boiling point and is how liquids like water turn into vapor.
Read more →Why does ice float?
Ice floats because it is less dense than liquid water. When water freezes, its molecules form a crystalline structure that takes up more space than liquid water, making ice less dense and causing it to float.
Read more →Why does water expand when it freezes?
Water expands when it freezes because water molecules form a hexagonal crystalline structure with more space between molecules than in liquid water. This open structure makes ice less dense, causing expansion.
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