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what is the boiling point of matter?
The boiling point of a liquid is the temperature at which it changes from a liquid to a vapor (gas). This happens in a pure substance when the vapor pressure is equal to the surrounding atmospheric pressure.
Water’s boiling point is 100 degC at one atmosphere of pressure, and its melting point is 0 degC. The boiling and melting points of other substances can vary depending on their composition, such as the presence of salt.
Freezing and Melting Points
As a solid, molecules are tightly packed and rigidly bonded together in a regular pattern. This structure prevents the molecules from moving freely. Once the particles reach a certain temperature, they break free of their binding and move more freely.
In contrast, liquids contain many more molecules that can vibrate freely. They are also tightly packed but without the symmetry that solids have.
Boiling Points Explained
A liquid’s normal boiling point is determined by its vapor pressure and the strength of intermolecular forces between its molecules. Larger covalent compounds have higher boiling points than smaller ones, as do polar molecules.
Molecular Shape and Size
The shape of a molecule slightly affects its boiling point. A molecule that is compact tends to have a lower normal boiling point than one that is larger and has more surface area.
The boiling and melting points of pure substances vary based on their purity. For example, saltwater has a different melting and boiling point than pure water because the sodium ions and chloride ions dissociate right away when dissolved. This can raise or lower the boiling and melting points by a few degrees.