What happens to make ice change into liquid and why does liquid water become a gas?

To understand why ice changes into liquid water and why liquid water becomes a gas, we need to look at the underlying concept of phase changes and the behavior of molecules.

Phase changes are the physical processes through which substances transition between different states of matter, such as solid, liquid, and gas. These transitions occur due to changes in temperature and/or pressure.

1. Melting (solid to liquid):
When ice is heated, its temperature increases. At a specific temperature called the melting point (0 degrees Celsius or 32 degrees Fahrenheit for water), the energy from the heat causes the molecules in the ice to gain enough kinetic energy to break their fixed positions and start moving more freely. This process is called melting, and the ice transforms into liquid water. The energy is used to overcome the intermolecular forces that hold the solid ice structure together, allowing the molecules to move past each other in a more fluid state.

2. Boiling or vaporization (liquid to gas):
When liquid water is heated, its temperature keeps rising. At a specific temperature called the boiling point (100 degrees Celsius or 212 degrees Fahrenheit for water at sea level), the energy from the heat causes some of the water molecules to gain enough kinetic energy to break free from the liquid phase and enter the gaseous phase. This process is called boiling or vaporization. The molecules escape with enough energy to overcome the intermolecular forces that held them in the liquid phase and move freely as a gas.

It's important to note that both melting and boiling occur at specific temperatures (melting point and boiling point) because they correspond to the point where the energy supplied overcomes the forces that hold the substances in their current phase.

Understanding phase changes and the behavior of molecules provides a scientific explanation for the changes from ice to liquid water and from liquid water to gas.