What happens to the boiling point of water when sugar is added?

When sugar is added to water, the boiling point of water increases. This phenomenon occurs due to a property of solutions known as boiling point elevation, which is one of the important colligative properties in chemistry.

The boiling point of a liquid is defined as the temperature at which its vapor pressure becomes equal to the external atmospheric pressure. Pure water boils at 100 °C (at standard atmospheric pressure). However, when a non-volatile solute such as sugar is dissolved in water, the solution formed has a lower vapor pressure compared to pure water. This happens because the sugar molecules occupy space at the surface of the liquid, reducing the number of water molecules that can escape into the vapor phase.

Since the vapor pressure decreases, the liquid must be heated to a higher temperature in order for its vapor pressure to equal the external pressure. As a result, the boiling point of the solution becomes higher than that of pure water.

This effect is not specific to sugar only; any non-volatile solute such as salt, glucose, or urea, when dissolved in water, raises its boiling point. The degree of boiling point elevation depends on the concentration of the solute particles in the solution, not on their type, which is why it is considered a colligative property.

For example, when sugar is dissolved in water for making syrups or jams, the boiling point of the mixture rises above 100 °C. This principle is also used in food preservation and in industrial processes where precise temperature control is required.

In summary, adding sugar to water increases its boiling point because sugar lowers the vapor pressure of water, requiring more heat energy for the liquid to boil. This explanation falls under the field of Chemistry, particularly the study of solutions and colligative properties.