Household bleaches – Term Paper

The main properties of cleaning agents

One of the most important properties of cleaning agents is their ability to act as cleaning agents during the cleaning process. A bleaching agent in chemistry is any cleaning agent that has the ability to remove coloured stains in clothes or the substance subjected to cleaning (Ebbing & Gammon 2016). There are different bleaching agents such as chlorine and oxygen with each having its own mechanism of bleaching. While chorine bleaches by reduction, the mechanism of bleaching in oxygen works by oxidation of the stains. The nascent oxygen atom released serves as the active component responsible for the bleaching in oxygen-based bleaches. Among the most common oxygen-based bleaches include the liquid hydrogen peroxide, sodium perborate and sodium percarbonate which are solid in nature.

With studies conducted on how solid oxygen bleaches work, it has been pointed that the solid oxygen bleaches, Sodium percarbonate (Na2CO3TZ1.5H2O2)) has the following properties: It is a colourless and crystalline compound that readily dissolves in water (Ebbing & Gammon 2016). It is also hygroscopic and thus able to draw water of crystallization. Studies have shown that dissolving Sodium percarboonate in water results to the formation of a mixture of sodium carbonate (soda ash) and hydrogen peroxide by decomposition. It is the tsoda asht that helps to maintain the PH of the solution within the right range and optimal point for the performance of the bleaching agent. The decomposition of hydrogen peroxide into water and a nascent (free) oxygen atom is responsible for the bleaching. Both oxygen and hydrogen peroxide have bleaching properties. They break down stains into smaller and more soluble components that are easily removed by the water molecules during the cleaning process. The two (hydrogen peroxide and oxygen) are also reduced in acidic medium to form water while in alkaline medium the two are further reduced to hydroxide ions (Ebbing & Gammon 2016). The performance and effectiveness of solid oxygen bleaches such as Sodium percarbonate are affected by a number of factors such as temperature of the water used during the cleaning process. This practical investigated the design of an experiment that aimed at solving the problem of whether the effectiveness of solid oxygen bleach in removing stains from fabrics is affected by the temperature of water used during the cleaning process.

Experiment with solid oxygen bleaches

The aim of the experiment was to investigate the effectiveness of solid oxygen bleaches in removing stains from fabrics affected by different water temperatures.

Hypotheses

Just like any other study, it is prudent to come up with hypotheses that would guide the investigation process. For this experiment, the following hypotheses served as the guide:

The higher the temperatures of the water bleach solution, the more effective it would be at removing the fabric stains

The more time allowed for exposure of the fabric in the bleaching agent, the more effectively the stains are removed

The higher the concentration of the bleaching agent, the higher the effectiveness and optimal performance of the bleach at removing the stains from the fabric

Dependent Variable

In conducting any given experiment, having a dependent variable that would be monitored is very crucial. In this case, the removal of stain was chosen as the dependent variable.

Independent Variable

The dependent variable varies with changes in the independent variables. For this experiment, temperature of the water used in the cleaning process was chosen as the independent variable

Controlled Variable

The controlled variables in this case were the following:

The amount of water used in the experiment was controlled by use of a measuring beaker to ensure that the amount used was the same throughout the experiment.

The time was also controlled using a stop watch to ensure the same time was observed for each measurement.

The amount of oxygen bleach was also accurately measured to ensure that the same amount of bleach is maintained.

Materials and Equipment

4 x 500 mL beakers

Solid oxygen bleach

Fabric (stained)

Stop watch

Water

Thermometer

Gloves

Apron

Method

Set up equipment and materials

Measure out 500 mL of water into each beaker and vary the temperature from cold to hot.

Add the same amount of bleach to each beaker and stir.

Add fabric to beaker and wait for 60 minutes.

Record results.

Results

The following results were obtained from the experiment:

Temperature Colour (1-10) Sample

Data Table 1:

Analysis of Results

The graph below shows how the colour changes on a scale of 1-10 against the temperature of the water used during the bleaching process:

Graph 1: A graph of hydrogen peroxide bleach against temperature.

How does oxygen bleach work  

Based on a careful analysis of the graph of colour change and the temperature of the water used, it is evident that the rate of hydrogen peroxide and oxygen decomposition increases with increase in temperature up-to a certain point (around 50oC) when the decomposition is almost complete. The direct relationship between decomposition and temperature change is due to the increase in kinetic energy which favours decomposition. The decomposition results to the release of the active ingredient from the solid oxygen bleach and hence the removal of the coloured stains in the fabric. However, it is noted that above 50oC, the removal of stains is not effective even with an increase in temperature since it is beyond the optimum point for bleaching and no further decomposition takes place beyond this point as can be observed from the graph.

It was prudent to control time in this experiment because increasing the time allowed for the completion decomposition and release of the active component in the bleach, the effectiveness of stain removal would have been affected. More stains would have been removed if time the fabric was exposed to the oxygen atoms was increased.

Fabric materials of the same type were used in this experiment as varying the material would have affected the results. This is because the material used in the fabric influences the adsorption of the bleaching agent molecules in reacting and dislodging the stains by the water molecules during the cleaning process.

Efficiency of household bleaches

This experiment proves that increasing the temperature of the water used to an optimum temperature of 50oC results to an improvement in the effectiveness of the bleaching power of the solid oxygen bleaches. Beyond the optimum temperature, the effectiveness reduces. In addition, the experiment proves that hydrogen peroxide and oxygen are effective bleaching components in solid oxygen bleaches. They work by oxidizing stain atoms loosening their bonding on the surface of the fabric and this allows the water molecules to dislodge them. The following reaction ionic reactions show how oxygen and hydrogen peroxide undergo reduction as they oxidize the stain molecules on the fabric:

H2O2 + 2H+ + 2e- t 2H2O

O2 + 4H+ + 4e- t 2H2O

The soda ash in the solid oxygen bleaches serves to maintain an alkali media that allows optimum performance of the bleach. It is however evident that following the decomposition of oxygen and hydrogen peroxide results to the formation of water which later on reduces oxygen molecules in alkaline medium to form hydroxide ions as shown by the reaction below:

O2 + 2H2O + 4e- t 4OH-

The hydroxide ions maintain the PH at an alkaline level thus allowing the optimal performance of the bleach. Since oxygen atoms used to oxidize the stains on the fabric does not result to fading gives oxygen-based fabric bleaches an advantage over the chlorine bleaches which fade easily.

References

Ebbing, D., & Gammon, S. D. (2016). General chemistry. Cengage Learning.