Saltwater freezes at lower temperatures than pure water (freezing point depression).Saltwater boils at slightly higher temperatures than pure water (boiling point elevation).Adding salt expands the liquid range of water, allowing saltwater to exist in a wider range of temperatures.
The phase diagram you sent compares the freezing and boiling points of saltwater solutions with different concentrations to pure water. Here are the key takeaways:
Freezing Point:
Pure water: Freezes at 0°C (32°F).
Saltwater: The freezing point decreases with increasing salt concentration. This phenomenon is known as freezing point depression. The more salt, the lower the freezing point.
Explanation: Salt disrupts the crystal lattice of ice, making it harder for water molecules to form ice crystals and lowering the freezing point.
Boiling Point:
Pure water: Boils at 100°C (212°F).
Saltwater: The boiling point increases slightly with increasing salt concentration. This phenomenon is known as boiling point elevation.
Explanation: Saltwater has stronger intermolecular forces between water molecules due to the presence of ions, requiring more energy to break these bonds and transition to the vapor phase, resulting in a higher boiling point.
Overall:
The phase diagram shows that adding salt to water expands the liquid region by lowering the freezing point and slightly raising the boiling point.
This allows saltwater solutions to exist in a wider range of temperatures compared to pure water.
Additional Notes:
The diagram might also show a eutectic point, which is the point of minimum freezing point for a specific salt-water concentration.
The specific values of freezing and boiling points for different salt concentrations will depend on the type and amount of salt present.