• Elevation Effect: The boiling point of pure water decreases by approximately 1.72°F (about 1°C) for every 1,000 feet increase in elevation due to the decrease in atmospheric pressure.
• Salinity Effect (Boiling Point Elevation): Adding salt raises the boiling point of water because the salt ions form attractions with the water molecules, requiring more energy (higher temperature) to turn them into vapor.
• Approximation: The salinity values are in percentages by weight. The increase in boiling point is a colligative property and depends on the molality (moles of solute particles per kilogram of solvent), not just the weight percentage. The values in the table for salinity are approximations based on typical behavior, as precise calculation requires specific formulas and the ebullioscopic constant for water at each specific pressure/elevation.
• Common minerals that might be present in water and affect the boiling temperature include: 
  • Calcium ions (
    Ca2+Ca raised to the 2 plus power

    Ca2+

    ): A primary component of “hard water,” typically found as calcium carbonate (

    CaCO3CaCO sub 3

    CaCO3

    ) or calcium sulfate (

    CaSO4CaSO sub 4

    CaSO4

    ).

  • Magnesium ions (
    Mg2+Mg raised to the 2 plus power

    Mg2+

    ): Another main component of hard water, found as magnesium chloride (

    MgCl2MgCl sub 2

    MgCl2

    ), magnesium sulfate (

    MgSO4MgSO sub 4

    MgSO4

    , also known as Epsom salt), or part of dolomite.

  • Sodium ions (
    Na+Na raised to the positive power

    Na+

    ): Often present with chloride to form sodium chloride (table salt), but also as sodium sulfate or sodium bicarbonate.

  • Potassium ions (
    K+K raised to the positive power

    K+

    ): Found in various salts, such as potassium chloride.

  • Carbonate and Bicarbonate ions (
    CO32−CO sub 3 raised to the 2 minus power

    CO2−3

    and

    HCO3−HCO sub 3 raised to the negative power

    HCO−3

    ): These react with calcium and magnesium to form limescale, a common deposit in kettles.

  • Iron compounds: Can be present in some water sources and contribute to dissolved solids.
    some minerals raise the boiling point more than others for the same concentration by weight because the effect depends on the

    number of dissolved particles (ions) they produce in the water, not just the total weight. This is a key principle of colligative properties. 

    Comparing Common Minerals 
    The primary factor determining the extent of boiling point elevation is how many ions the mineral compound dissociates into: 
    • • Sodium Chloride (

        

        NaClNaCl

        NaCl

        ): Dissociates into two ions: one

        

        Na+Na raised to the positive power

        Na+

        and one

        

        Cl−Cl raised to the negative power

        Cl−

        ion.

      • Calcium Chloride (

        

        CaCl2CaCl sub 2

        CaCl2

        ): Dissociates into three ions: one

        

        Ca2+Ca raised to the 2 plus power

        Ca2+

        and two

        

        Cl−Cl raised to the negative power

        Cl−

        ions.

      • Magnesium Chloride (

        

        MgCl2MgCl sub 2

        MgCl2

        ): Dissociates into three ions: one

        

        Mg2+Mg raised to the 2 plus power

        Mg2+

        and two

        

        Cl−Cl raised to the negative power

        Cl−

        ions.

      • Sodium Phosphate (

        

        Na3PO4Na sub 3 PO sub 4

        Na3PO4

        ): Dissociates into four ions: three

        

        Na+Na raised to the positive power

        Na+

        and one

        

        PO43−PO sub 4 raised to the 3 minus power

        PO3−4

        ion. 

    Which Raises it More? 
    • • Per unit of weight (mass percentage):

        • • 

            CaCl2CaCl sub 2

            CaCl2

            and

            

            MgCl2MgCl sub 2

            MgCl2

            raise the boiling point more significantly than

            

            NaClNaCl

            NaCl

            because they produce more ions per formula unit and also have lower molar masses per ion compared to

            

            NaClNaCl

            NaCl

            . For the same weight of mineral, you get more total dissolved particles with

            

            CaCl2CaCl sub 2

            CaCl2

            or

            

            MgCl2MgCl sub 2

            MgCl2

            than

            

            NaClNaCl

            NaCl

            .

          • Minerals like sodium phosphate (

            

            Na3PO4Na sub 3 PO sub 4

            Na3PO4

            ) are even more effective per unit weight because they release four ions.

      • Per molar concentration (same number of moles):

        • • 

            CaCl2CaCl sub 2

            CaCl2

            would raise the boiling point about 1.5 times as much as

            

            NaClNaCl

            NaCl

            because it yields 3 ions versus

            

            NaClNaCl

            NaCl

            ‘s 2 ions. 

    In summary, minerals that break down into a greater number of ions when dissolved in water will have a more significant impact on raising the boiling point compared to those that produce fewer ions at the same concentration by weight. 
  • Adding

    sugar to water increases its boiling point. This effect, known as boiling point elevation, is a colligative property, meaning it depends on the concentration of the dissolved sugar particles (solute) in the water (solvent). 

    The Science Behind It 
    • • Vapor Pressure Lowering: When sugar molecules are dissolved in water, they occupy space at the surface of the liquid and create attractions with water molecules. This makes it harder for the water molecules to escape into the gas phase (vapor) at a given temperature, which lowers the vapor pressure of the solution compared to pure water.
      • Higher Temperature Required: Boiling occurs when the vapor pressure of the liquid equals the external atmospheric pressure. Because the sugar solution has a lower vapor pressure, it must be heated to a higher temperature to reach atmospheric pressure and boil.
      • Concentration Matters: The higher the concentration of sugar, the greater the number of dissolved particles, and therefore the higher the resulting boiling point. This principle is the basis of candy making, where different temperatures (and thus different sugar concentrations) yield different candy textures (e.g., soft ball vs. hard crack). 
        

         

        Sugar vs. Salt 

        Sugar (sucrose,

        C12H22O11C sub 12 H sub 22 O sub 11

        C12H22O11

        ) is a non-electrolyte, meaning its large molecules dissolve but do not dissociate into ions in the water. Salt (

        NaClNaCl

        NaCl

        ), on the other hand, dissociates into two ions (

        Na+Na raised to the positive power

        Na+

        and

        Cl−Cl raised to the negative power

        Cl−

        ). 

        • • For the same number of moles, salt raises the boiling point almost twice as much as sugar because it produces twice as many particles.
          • However, because a sugar molecule is much larger than a salt ion, more sugar molecules can be added per gram than salt ions, so at very high weight percentages (as in candy making), sugar solutions can reach significantly high boiling points (up to 300°F or more). 
        Approximate Boiling Points (at Sea Level, 0 ft) 

        Sugar Concentration (by weight)	Approximate Boiling Point (°F)
        0% (Pure Water)	212°F (100°C)
        60%	~217°F (103°C)
        80%	~230°F (110°C)
        90%	~248°F (120°C)
        99%	~300°F (149°C)

     

Volitiles

• Volatility: Unlike salts and sugars, which are non-volatile (they don’t easily evaporate), alcohols are volatile (they evaporate more readily than water).
• Lower Boiling Point: Common alcohols like ethanol (boiling point ~78°C or 173°F) and methanol (~65°C or 149°F) have a lower boiling point than pure water (100°C or 212°F).
• Azeotropes: The mixture of alcohol and water does not have a single fixed boiling point that gradually increases like a salt solution. Instead, the mixture boils over a range of temperatures, and the composition of the vapor is different from the liquid. This process is complex and often forms an azeotrope, a specific mixture concentration (e.g., about 95.6% ethanol by weight) that boils at a constant temperature lower than either pure component’s boiling point (~78.2°C). 

1. Lower Overall Boiling Range: When mixed, the alcohol molecules disrupt some of the strong hydrogen bonds between water molecules. This makes it easier for molecules to escape into the vapor phase, lowering the vapor pressure of the solution and thus lowering the boiling temperature.
2. Alcohol Evaporates First: Because the alcohol has a lower boiling point, the vapor produced during boiling is richer in alcohol than the liquid mixture itself.
3. Changing Composition: As the alcohol boils off, the remaining liquid becomes more concentrated in water. Consequently, the boiling point of the remaining liquid gradually increases over time until only pure water (or the azeotrope mixture, depending on the initial concentration) is left, boiling at its normal temperature.