The effects of salts on the freezing point of liquids

The effects of salts on the freezing point of liquids
The effects of salts on the freezing point of liquids

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The effects of salts on the freezing point of liquids


Freezing refers to the process of substance changing from liquid to solid. This occurs when liquid molecules slows down, making their attraction occur in a way that they arrange themselves in a fixed position- solid (University, 2014).  Therefore, this activity explores the concept of freezing point of liquids and how it is affected by impurities (salts). This helps in focusing on the interactions that takes place at molecular level of a solution as it freezes (Pedersen and Myers, 2010).


What are effects of salts on freezing point of liquids?


 Salts affect lowers the freezing point of liquids

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Data/ Discussion

In this experiment, the following materials are used; tape, marker; 2 cups; 2 ice cubes, timer and half tea spoon of salt.  The tape and the marker were used to label the cups, “No salt” and “salt.”  The ice cube is placed in each of the cup; salt was added in the cup marked “salt”. The procedure was done three times.  The temperature of each cup and other physical observation was made after every 10 minutes for thirty minutes.  The data obtained was recorded as shown in the table below (VanCleave, 2002):

Time (minutes Temperature recorded in salt cupTemperature recorded in non-salt cup
Starting0.1º C0.1º C
10 min-3 C0.1º C
20 min– 4º C0.0º C
30 min– 4º C0.0º C
Average– 3.5º C0.01º C

After thirty minutes mark, it was observed that the cup containing salt begun to melt; whereas the other cup containing no salt consisted of completely frozen solid. The temperatures recorded indicated that the temperatures of the frozen ice reduced in cup containing salt. Whereas the average temperature of the frozen ice without salt is 0.1º C; the temperature for the cup containing salt lowered by 3-4 degrees Celsius lower that of the control experiment (VanCleave, 2002).

 This can be concluded that salts lower the freezing point of water.  The differences in observed temperature with theoretical temperature are attributable to differences in atmospheric pressure. However, the difference is negligible (Pedersen and Myers, 2010). This is because in low temperatures, water molecules slow down. These molecules move slow making the intermolecular attractions between the molecules become very strong, forming a lattice of water molecules which becomes ice.  During the freezing temperature, the rate at which the molecules enter and leave is same (University, 2014).

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However, on addition of salt, the equilibrium is disrupted. This is because with the addition of salt, there is less water molecules, due to the interface of solute and solution. This implies that the solute particles block the interaction of the water molecules, thus, more water are leaving and less water are re-entering the solid phase. As the temperature continues to lower even further, the water molecules leaving the solid state slow down even further. This describes the concept of freezing point depression (Rawn and Ouellette, n.d.).

 Freezing point depression refers to the process where addition of a salute to a solvent causes a decrease in the solvent freezing point. Other examples include alcohol in water and mixing of any impurity in a solvent. This is the phenomenon that causes the sea water (presence of impurities) to remain liquid even during temperatures below 0ºC (University, 2014).

This concept has many uses. For example, it is used to ensure that automobile radiator fluid does not freeze during winter. This is because the radiator fluid is a mixture of alcohol and water. Road salting during winter is also an application of freeze-point depression, as the salt lowers the freezing point of snow, making it melt; thus preventing the accumulation of snow during winter (Pedersen and Myers, 2010).

However, it is imperative to note that the maximum depression of freezing water of sodium chloride (commonly used) is -21ºC; therefore, for ambient temperatures that are lower, sodium chloride is ineffective. However, other salts such as calcium chloride, mixture of many and magnesium chloride can be used, as the phenomenon concept is the sale.

However, these other salts are corrosive, especially on iron, and in some places, safer salts should be used (Rawn and Ouellette, n.d.). Additionally, it is imperative to note that the exact depression of the freezing point depends on the amount of salt used. Literature indicates that 0.5 mol of NaCl lowers freezing point by 1.65º C, but the maximum depression temperature is -21º F, which is a approximately -6º C (Pedersen and Myers, 2010).


 The study hypothesis is proven; salts lowers the temperature at which the fluid (water) freezes.  The reason behind this is probably because the molecule interaction of pure water is different from the molecule interaction in presence of salt.  This makes the salt water to have different chemical properties as the salt joins in the interface between the Hydrogen and Oxygen bond, making the interaction of these two molecules less strong (Rawn and Ouellette, n.d.).


Pedersen, S. and Myers, A. (2010). Understanding the principles of organic chemistry. Belmont, CA: Brooks/Cole Cengage Learning.

Rawn, J. and Ouellette, R. (n.d.). Organic chemistry.

University, O. (2014). Seawater. Jordan Hill: Elsevier Science.

VanCleave, J. (2002). Janice VanCleave’s help! my science project is due tomorrow!. New York: Wiley.

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Scientific Experiment Lab Report

Scientific Experiment Lab Report
Scientific Experiment Lab Report
Scientific Experiment: The effect of varied intensities of light on the growth of a sunflower plant



The purpose of this scientific experiment was to conduct an investigation in order to determine the effect of varied intensities of light on the growth of a sunflower plant. This is of significant relevance because it would enable the determination of the appropriate light intensity exposure for specific plant species, which is imperative for optimal plant growth to be achieved.


Sunflowers are seed-producing herbaceous plants. The sunflower plants are dichotomous angiosperms; therefore, this means that they produced both flowers as well as seeds, which are attached or carried in the flower part of the sunflower plant. The basis of sunflower reproduction is through its seeds (National Sunflower Association, 2007).

When planted, these sunflower seeds under necessary conditions usually grow to form other sunflower plants. According to National Sunflower Association (2007), sunflower plants have composite flowers, which are composed of numerous smaller florets; which means in a sunflower each petal is actually a distinct floret.

Literature Review

Sunflower plants are native to South and North America, and have their cultivation has been practiced since around 3000 BC (National Sunflower Association, 2007). According to Masefield et al. (1999), oil extracted from sunflower seeds is the chief reason for the cultivation of sunflowers plants today, and the extracted oil is used for cooking as well as in the manufacturing of soaps. National Sunflower Association (2007) reported that the name of sunflowers was coined from the ability of unopened flowers of the sunflower plants to turn and face the sun throughout the day from the time it arises to the time it sets, which increases the number of daylight hours that sunflowers receive.

Like other plants, sunflower plants photosynthesize to obtain energy and food from the sun as well as carbon dioxide from the atmosphere, while releasing oxygen to the atmosphere as the reaction’s waste product. The reaction shown below uses energy and carbon dioxide from ultraviolet radiation and atmosphere respectively to synthesize carbohydrates, which are useful for the growth of the plants (Vendrame, Moore & Broschat, 2014). Therefore, since the atmosphere has abundant carbon dioxide, the amount or intensity of light exposure per day could be the determinant factor that limits the growth of plants.   

CO2 + energy → O2 + starch

Light intensity has the possibility of affecting plant form in terms of plant growth, flowering, leaf color and size in both woody and herbaceous species. Shade tolerant plants have both physiological and morphological adaptations that are essential in allowing them towards adapting to low-light conditions (Schwartz, 2007). However, phenotypic responses to light intensities can be varied within a plant species, which suggests that appropriate selection of the plant species may allow for cultivars to develop that have enhanced tolerance to shade or low-light conditions.

Furthermore, plant response to different light intensities can also be varied among genotypes within a plant species (Smith, 2012). Therefore, this experiment is an important scientific inquiry which is greatly essential in determining how varied light intensity conditions can affect the growth of plant species, including sunflower plants selected for this experiment.

However, an increase in the amount or intensity of light that is received by a plant will not necessarily increase its growth for a long time. This is mainly because at excessive levels of light exposure, the plant leaves often begin to shrivel and wilt, causing the plant distress which hinders continued growth (Squire & Sutherland, 2013). Therefore, most plants usually show an increased rate of growth as light exposure is also increased, but an abrupt decrease in their growth will be observed past a certain light exposure threshold.


If sunflower plants are exposed to 4 hours, 6 hours, 8 hours, 10 hours or 20 hours of ultra violet light per day, it is hypothesized that their tallest growth will be observed in the 10 hours per day experimental condition since the extra hours of daily exposure to ultra violet light will allow photosynthesis of more carbohydrates by the plants; therefore, this will enable them to have the tallest growth when the heights of the seedlings is measured in centimeters.

Alternatively, if the sunflower plants are exposed to too much ultra violet light, such as 20 hours daily exposure to light sample, then their growth will be shorter compared to other plants, because prolonged exposure to ultra violet is damaging.   

Materials and Method

According to Einstein, Newton and Hawking (2006) and Squire and Sutherland (2013), it is very important for all the steps stipulated in the lab manual for the scientific experiment to be stringently followed and adhered to in order to ensure that credible, reliable, valid and reproducible results are obtained. The materials needed for this scientific experiment included: 100 grams of sunflower seeds; 5 plant pots; soil thoroughly mixed with manure and water.

In this experiment, sunflower seeds are planted in 5 separate plant pots filled with soil that is thoroughly mixed with manure and watered frequently. Upon germination, the experimental conditions of varied light intensity were introduced to the 5 different plant pots already with young sunflower plants including 4 hours, 6 hours, 8 hours, 10 hours, and 20 hours of light exposure per day respectively. The heights of the sunflower seedlings were taken from the 5 plant pots after week 1, week 2, week 3 and week 4; and the measured heights were recorded.


Table 1: A Table of Seedling Heights

Hours of Light Per DayWeek 1 (cm)Week 2 (cm)Week 3 (cm)Week 4 (cm)

A line chart was plotted for the results obtained in the scientific experiment to visually represent the heights of the sunflower seedlings in centimeters after week 1, week 2, week 3 and week 4 with regards to hours of light exposure per day which are 4 hours, 6 hours, 8 hours, 10 hours and 20 hours respectively. The plotted line chart is illustrated in Figure 1 shown below:

Figure 1: A Line Chart of Seedlings Heights

The results illustrated in Table 1 and Figure 1 show that as the amount of or exposure to light is increased through prolonged hours of light per day, there was an increase in the growth of the sunflower plants, with the exception of the sunflower plants that were exposed to 20 hours of light per day, in which less growth was observed. With increasing light exposure from 4 hours to 10 hours per day, there was an exponential increase in the plant height, but the plant height was the least at 20 hours of light exposure per day.


The experiment results for between 4 and 10 hours of light exposure per day affirmed my proposed hypothesis that the growth of plant increases with increasing exposure to light. In the lowest light exposure or intensity experimental condition, there were only 4 hours per day in which the sunflower plants received light; and as shown in Table 1, the plant height growth was 7 cm. Moreover, the height of sunflower plants that received 6 and 8 hours of light exposure per day grew by 11 and 10 cm respectively. However, the optimal growth of the sunflower plants’ heights was observed in those that received 10 hours of light exposure per day experimental condition, which support the proposed hypothesis.

Alternatively, shortest growth in height was observed in the sunflower plants that were exposed to 20 hours of ultra violet light per day experimental condition, with a height of 6 cm. There was also a yellowish color observed in the leaves of these sunflower plants compared to their counterparts that were exposed to less light, which had bright green leaves suggesting that the extra hours of light exposure have a damaging effect to the leaves of the sunflower plants subsequently preventing them from thriving. This affirms with the known characteristics and behaviors portrayed by plants when subjected to excessive exposure of light (Squire & Sutherland, 2013).  


During the scientific experiment that was performed to investigate how the amount or intensity of light exposure the sunflower plants received is related to their heights of growth for varied hours of light exposure per day over a period of four weeks. Sunlight exposure of the sunflower plants to between 4 and 10 hours per day made the height of the plants to grow taller as the hours of light exposure were increased. This is in concurrence with the proposed hypothesis that increased light exposure encourages plant growth, but not beyond the threshold level after which further increase in light exposure damages the plants.         


Einstein, A., Newton, I., & Hawking, S. (2006). Biology 083 Lab Manual. Vancouver, BC: Vancouver Community College.

Masefield, G. B., Nicholson, B. E., Harrison, S. G., & Wallis, M. (1999). The Oxford Book of Food Plants. London, UK: Oxford University Press.

National Sunflower Association (2007). All about Sunflower. Retrieved from:

Schwartz, B.  (2007). Filling the shadows with light. American Nursery Management, 185(8), 44-51.

Smith, H. (2012). Light quality, photo-perception, and plant strategy. Annual Review Plant Physiology, 33(2), 481-518.

Squire, D. & Sutherland, N. (2013). The Step by Step Guide to Houseplant Care. Vancouver, BC: Whitecap Books Ltd.

Vendrame, W., Moore, K. K., & Broschat, T. K.  (2014). Interaction of light intensity and controlled-release fertilization rate on growth and flowering of two New Guinea impatiens cultivars. Horticultural Technology, 14(3), 491-495.

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Environmental Pollution: Case Study of Lagos Nigeria

Participatory Approach to Monitoring Air Quality

Environmental Pollution: Case Study of Lagos Nigeria

As it is evident today, the increased exposure to harmful environmental pollution resulted from irresponsible human activity. Environmental pollution can be categorized into diverse forms. This includes water, air and soil pollution. Other forms of industrial pollution encompass heavy metal and chemical pollution as well as occupational pollutants. There is no doubt that air pollution is the primary accelerating factor behind global climate change in both developed and developing nations.

The air pollution menace is apparently emerging as a complex phenomenon driven by persistent failure of the global environmental management initiatives that have been created to stem the runaway trend currently witnesses in major cities worldwide. The Lagos state metropolis is currently facing myriad air pollution related problems most notably due to rapid urbanization and road traffic emission.

The devastating effects of this observable fact are more prominent in the metropolitan cities of the developing than developed nations. Lagos, a rapidly growing megacity in Nigeria hasn’t been spared the brunt of air pollution. As an emerging metropolis, and its phenomenal rise as an epitome of industrialization and commercialization on the African continent, many predictions indicate a looming danger due to the adverse effects of climate change that is emanating from persistent industrialization related pollution.

Although significant effort has been directed towards stemming the runway global pollution levels, challenges have continued to constraint this effort largely due to insufficient program funding. Subsequently, there is sufficient evidence that warrants a thorough review of the literature on the adverse environmental impactsof air pollution, its principle role as an agent of climate change and its adverse effects on the health and wellbeing of the crowded inhabitants of Lagos.

 This research will specifically focus on air pollution. Current literature suggeststhat pollution is the world’s largest environmental cause of poor health responsible for an estimated 9 million premature deaths in 2015-2016 and large burden of non-communicable disease, including respiratory, cardiovascular and neurological impairment. Air pollution, combining both ambient and household air pollution (HAP) is responsible for 6.5 million deaths per year with another 7 million from tobacco smoke and this number will increase is urgent measures are not taken.

Monitoring and management of air pollution remains ineffective and poorly enforced due to a number of factors.Monitoring equipment can be expensive and requires regular checking and maintenance, while enforcement in a growing megacity of 16 million people and unknown numbers of businesses is a major challenge. An alternative approach to the ‘top down’ processes of monitoring and enforcement would be to encourage a more community-led approach and local action.

However, there are many questions as to how such a ‘grassroots’ approach would work in practice, and there are many knowledge gaps as to their applicability for measuring air pollution in the megacities of the developing world. The research seeks to address some of these gaps in knowledge by first exploring how local communities can assess the level of air pollution and its environmental impacts. Subsequently, there is need to identify indicators of air quality that are used by communities, even if they may tend to be more qualitative than quantitative.

An example could be the frequency at which clothes and indeed furniture, windows etc., in household buildings become dirty. Indicators of the effects could be related to health and may include breathlessness. Communities will be asked to identify indicators of relevance to them, and these will be ranked. It is possible that the choice and ranking of these indicators will be influenced by social factors such as gender and age. Currently, the exposure to harmful environmental pollution is created through human activities. Mobile Air measurement System: This advanced equipment employs geospatial technology thus it is referred to as Geospatial Measurement of Air and Pollution (GMAP).

Air pollution is one of the major environmental challenges that Nigeria faces today. This phenomenon is threatening the socio-economic development gains that have been made since independence. The number of power plants has grown to unprecedented levels whereas mortality rates resulting from low quality air have continued to rise. Reports indicate that environmental pollution can be linked to the recent upsurge in cardiovascular diseases as well as other respiratory complications.

Nevertheless, the primary causes of environmental pollution are activities linked to industrialization such as extraction, transportation and the export of oil at the Gulf of Guinea. Similarly, traffic, rapid industrialization and gas flaring are the most common causes of air pollution in Nigeria. Thus pollution is adversely affecting different sectors such as health and environment, and has been linked to the destruction of ecosystems and climate change among other socio-economic ills.

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