Effects of Additives on Boiling Rate

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Water additives refer to minute quantities of a substance added to water to either improve its taste, preserve it or for other experimental reasons. Water is a colorless, naturally available chemical substance covering most of the earth’s surface. Some additives in mineral water include calcium chloride, magnesium chloride, oxygen and potassium chloride usually for preservation (Watson, 1992).

Problem statement

Boiling rate is the point at which the solution will turn into vapor (Gauntt, 1990). This is a point where the solution will change its state from liquid to gas due to the increased kinetic energy of its molecules (United States, 1997). The boiling rate of a substance, such as water and additives, are affected by their densities, pressure, quantity of additive, time taken to heat and the temperature. Additives such as salt, sugar, radiator cooler, super coolant water wetter and others can be added to water during experiments to test their effects on boiling rate as in this case. The boiling point of pure water, 100°C at atmospheric pressure, is used in this experiment as a control to determine time taken for water to reach boiling point with different additives. Additives to be inputs in this experiment are salt and sugar together with other substances.

Literature Review

The experiment seeks to determine the importance of additives in car coolant systems. Car engines require cooling for optimum performance. High temperatures in the engine can cause it to knock out. The experiment will provide an approach in which manufacturers of car coolant systems and additives to produce products which ensure effective cooling systems.

Experimental Design Steps

The procedures involve;

Boiling one liter of pure water until 100°C and measure the time it takes to reach that point. Repeat it twice for quality assurance. Use this as a control experiment.

Mix the same amount of water, one liter, with the additives to make a solution.

Heat the solution in a constant supply of heat until it reaches boiling point.

Measure the time taken to reach boiling point.

Repeat the same experiment twice and note any differences and average it.

After every experiment, add more of the additive and observe whether there is a change in the period for which the solution to reach boiling point.

Recording findings of the experiments.

Analysis of data to generate information to support the thesis statement.

Report and recommend.

Assumptions made;

Room temperature is 20°C

At one atmospheric pressure conditions

The amount of energy supplied is 4.18 joule/minute/°C.

The same amounts of water are used for all the experiments. One liter of water.

The quantity of additive added each time is 10grams.


When 4.18 joules of energy is used to heat 1 liter of water, it takes 80 minutes to raise the temperature from 20°C, room temperature, to 100°C. The density of pure water is 1g/cm3under normal temperatures and pressure. Temperature affects the movement of water molecules thus under hot conditions the movement is faster making it less dense. Pure water boils when it reaches a temperature of 100 °C. When more pressure is applied to water during boiling, the boiling rate tends to increase.

The presence of additives of different types and quantities demonstrate the effects to boiling rate in a more comprehensive manner (Aslam, 2015). Additives can be in the form of solutes or solvents. A solute is a substance which can dissolve a solvent. A solvent is material in which solutes dissolve in it. In this experiment salt and sugar are used to experiment the phenomenon.

Sequence of Events

When 4.18 joules of energy are used to heat 1 liter of water in which 10 grams of table salt is dissolved in it. The total time taken for the salt solution to boil is 82 minutes. The boiling point is at 103°C. When more salt, 10g, is added to the solution, the time to reach boiling point increases to 83 minutes. The boiling point also increases to 105°C. Salt solution with a moderate concentration, has an average density of 1.05g/ cm3under normal temperatures at a given quantity of salt. Salty water has a higher boiling rate than pure water due to the slow movement of molecules during boiling (Pilson, 2013).

Threat reduction to internal validity

This can be slightly above 100 °C as shown by the experiment. The more the salt is added to the solution; the higher the rate of boiling due to increased density. The addition of 10g of salt to 1 liter of water will result to an increase in the boiling rate by 0.09 °C. More time will also be required to allow the water molecules acquire adequate kinetic energy to make them escape from the solution. The boiling rate can however be reduced when the pressure is lowered.


When 4.18 joules of energy are used to heat 1 liter of water, in which 10grams of sugar is dissolved in it, the time taken to reach boiling point is 84 minutes. The boiling point is 104.5°C.Sugar is a solute which can be added to water to make a solution. The density of a sugar solution is 1.58g/ cm3.

Process of Data Collection

 This means that a sugar solution is denser than water. The time increase to reach boiling point is as a result of more energy required to make the water molecules escape from the solution. The boiling rate of the sugar solution will thus be above 100°C (CRAPISTE, 1988).The addition of more sugar, 10g; to the 1 liter sugar solution will increase the boiling rate by 0.31 °C and the time to reach boiling point also increases. The boiling point can however be reduced by lowering the pressure.

Data Table


Capacity of water (litres)

Mass (grams)

Time (minutes)

Temperature (degrees)

Density of water ()







The results of the three experiments reveal that, additives with higher densities than water tend to lead to increased average densities of the solutions and hence increased boiling rates. The higher the density of an additive, the more the time it takes to reach boiling point. Based on these results, we can find out that additives with lower densities than water will result in less time required to reach boiling point. The boiling point also reduces to less than 100°C. For instance kerosene and oxygen mixed with water will result in less time to reach boiling point when the experiments involving the additives such as oxygen are undertaken in air tight conditions.


Kerosene is a solvent with a density of 0.79g/cm3 at normal temperatures. The mixture of kerosene and water will give a density of 0.89g/ cm3   which is less than the density of water. The boiling rate of the mixture will reduce. (Gauntt, 1990), further addition of more kerosene will cause a decline in the boiling rate. Kerosene boils at the rate of about 60 °C. It will take less time to reach boiling point since less energy is required to make the water molecules to escape from the mixture.

Oxygen is naturally dissolved in water.  The density of oxygen is less than 0.71g/l. it implies that oxygen is less dense than water. When water-oxygen solution exists, the density is around 0.8g/l. The boiling rate should be less than 100°C. Oxygen escapes immediately when water is heated but for experimental purposes, the container should be made air tight (Gauntt, 1990). When more oxygen is added, the average density will reduce hence further reduction in the boiling rate.


Confirmation of Hypothesis

In fuel combustion, a lot of heat is usually generated, thus temperatures are high. The fuel turns to vapor and its density reduces. At this point it has reached boiling point. The excess heat need to be radiated away from the ignition system. This means that there is a transfer of heat from the combustion chamber to the cooling system. The efficiency in the car cooling system determines effective cooling of the engine.

Experimental Design as a Key Factor

This is the reason behind the use of cooling additives in car cooling systems. An additive will enhance the capacity of water in the engine to transfer heat by reducing the time to reach boiling point. Water also has oxygen dissolved in it which causes rusting but the additives also prevent rusting. Examples of coolant additives are water wetter, radiator relief, super coolant and radiator coolant.

In conclusion; it is true that different additives affect the boiling rate of water since differential in densities coupled with additives’ quantities and the atmospheric pressure, the energy required by the molecules to escape from the solutions varies causing changes in boiling rates.


Additives with higher densities than water, mostly solutes, tend to increase the boiling rate of water on dissolving. (Aslam,2015), the more the solute is added, the higher the boiling rate since the molecules requires more kinetic energy to escape from the solution. The time taken to reach boiling point is high. These additives are not efficient in car cooling systems since their efficiency in transferring heat from the engine is low.

Additives with lower densities than water, mostly solvents, tend to decrease the boiling rate of water when mixed. When more of the additive is added to water, the density reduces hence a lower boiling rate is observed. This is because the mixture molecules require less energy to escape from the mixture. The time taken to reach boiling point is reduced. Coolants from these additives are efficient in heat transfer and cooling of engines.

Evaluation of Validity

When the atmospheric pressure increases, the boiling rate increases and vice versa (United States, 1997). In case of high atmospheric pressure, more energy is required to vaporize the liquid or for it to reach boiling point. Pressure in combustion chambers is used to reduce density of fuels so that they reach boiling point faster since energy requirement is reduced.


Aslam, M., Kothiyal, N. C., & Sarma, A. K. (January 01, 2015). True boiling point distillation and product quality assessment of biocrude obtained from Mesua ferrea L. seed oil via hydroprocessing. Clean Technologies and Environmental Policy : Focusing on Technology Research, Innovation, Demonstration, Insights and Policy Issues for Sustainable Technologies.

CRAPISTE, G. H., & LOZANO, J. E. (May 01, 1988). Effect of Concentration and Pressure on the Boiling Point Rise of Apple Juice and Related Sugar Solutions. Journal of Food Science.

Pilson, M. E. Q. (2013). An introduction to the chemistry of the sea. Cambridge: Cambridge University Press.

Sandia National Laboratories., U.S. Nuclear Regulatory Commission., United States., Gauntt, R. O., & Gasser, R. D. (1990). Results of the DF-4 BWR (boiling water reactor) control blade-channel box test. Rockville, Md: U.S. Nuclear Regulatory Commission.

United States., & United States. (1997). Pressure suppression containment system for boiling water reactor. Oakland, Calif: United States. Dept. of Energy. Oakland Operations Office.

Watson, P. J., Tuzinski, P. A., & United States. (1992). Study of zeta potential for material particles in chemical additive solutions. Washington, D.C: U.S. Dept. of the Interior, Bureau of Mines.

October 05, 2023



Scientific Method

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