What is Melting and Boiling? | Types, Definition, Structure, Function & Facts

What is Melting and Boiling?

Solids, liquids, and gases, all matter exists in certain states or phases. Water can be liquid water, solid ice, or gaseous vapor. However, it is still water and consists of molecules consisting of 2 hydrogen atoms and 1 oxygen atom (H2O).

Melting and Freezing

When a solid turns into a liquid, it is called molten. There is a temperature at which this happens called the melting point. As the energy of the molecules increases due to the increase in temperature, the molecules start to move faster. Soon, they have enough energy to break free of their rigid structure and begin to move more easily. Matter becomes liquid. The melting point of water is 0 degrees Celsius (32 degrees Fahrenheit).

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When the opposite happens and the liquid turns into a solid, it is called freezing.

Boiling and Condensation

When a liquid becomes a gas, it is called boiling or evaporating. Again, at a certain temperature called the boiling point, the molecules gain enough energy to escape and become a gas. The boiling point of water is 100 degrees Celsius (212 degrees Fahrenheit).

When the opposite happens and a gas becomes a liquid, it is known as condensation.


Evaporation is the phenomenon in which a liquid becomes a gas that occurs only on the surface of the liquid. Evaporation does not always require high temperatures to occur. Although the overall energy and temperature of the liquid may be low, the molecules on the surface in contact with the air and gas around them can be high in energy. These molecules on the surface will slowly become gas through evaporation. You may see evaporation as the water dries on your skin or a puddle on the road gradually disappears.

Standard State

Scientists use the term “standard state” to describe the state of an element or substance under “ambient conditions” of 25°C and an atmosphere of atmospheric pressure. Most elements, such as gold and iron, are solids in the standard state. Only two elements are liquids in the standard state: mercury and bromine. Some elements are gases in their natural state including hydrogen, oxygen, nitrogen, and noble gases.

Fun facts about Melting and Boiling

When rocks become very hot, they turn into a liquid called magma or lava.

Gases can be converted to liquids by pressure. By squeezing all the gas molecules tightly, a gas can become a liquid.

We use natural gas indoors in the gaseous state, but when it is transported by tanker, it is transported in the liquid state to save space.

Mercury has the interesting properties of being both a metal and a liquid in the standard state.