1. Increased Molecular Motion:
* Low Heat: At low temperatures, water molecules are relatively close together and move slowly. They are primarily held together by hydrogen bonds.
* Adding Heat: As heat is added, water molecules absorb energy, causing them to move faster and vibrate more vigorously. This increased kinetic energy weakens the hydrogen bonds between molecules.
2. Phase Changes:
* Melting: When enough heat is added to overcome the hydrogen bonds holding water molecules in a solid (ice) state, the ice melts into liquid water. The molecules are now free to move around each other, though they are still attracted to each other.
* Boiling: As the water is heated further, the molecules gain even more energy and overcome the attractive forces. When the temperature reaches 100°C (212°F) at standard atmospheric pressure, the water boils. The molecules break free from the liquid state and escape into the air as water vapor (gas).
3. Expansion:
* Liquid Water: As water is heated, it expands. This is because the increased molecular motion causes the molecules to spread farther apart.
* Vapor: Water vapor expands much more readily than liquid water, as the molecules are now essentially independent and move freely.
4. Evaporation:
* Even below the boiling point, some water molecules at the surface have enough energy to escape into the air. This is called evaporation. Warmer water evaporates faster because more molecules have enough energy to overcome the attractive forces holding them in the liquid state.
In Summary:
Heating water causes its molecules to move faster and break free from the bonds holding them together, leading to changes in its state (from solid to liquid to gas) and expansion.
