Lab Report Sample on pH

📌Category: Chemistry, Science
📌Words: 969
📌Pages: 4
📌Published: 01 June 2022

The data from Graphs One and Two display a correlation between pH level and catalase function. The curve of best fit visualises a steady, exponential increase, with the highest point appearing to be between pH 7 and 9, followed by a large decrease in the data values. It is evident that as the pH level of the hydrogen peroxide solution increases, the volume of foam produced from the catalase reaction increases, until a certain point, when a significant decrease occurs. As seen in Table One, when the pH level is shown at 3, the average volume of foam produced at the 1-minute mark is 48.14mL, whereas at pH level 9 the average volume of foam is 59.14mL.

 

DISCUSSION: Results

Scientific literature (Lecornu & Diercks 2017; Gillespie 2018; BBC 2022) states that catalase functions optimally between pH 7 and 11, however, it can be assumed optimal when replicating the pH of a lamb liver. The results show a defined pattern; catalase function steadily increased as the pH level increased, before plateauing at pH 11. While Graph One shows several average values at pH 7 that exceed lower pH levels, these are then exceeded by average values at pH 9. This is reinforced by Table One, as at the 1-minute mark, pH 7 had produced 53.86mL of foam, while pH 9 had produced 59.14mL. Contradictory, at 2 minutes, Table One shows that pH 7 had exceeded the foam production of pH 9 by 0.13mL. Graph Two displayed that pH 7 had the largest foam volume, excluding an outlier from pH 5. The average data at 2 minutes supports literature but at 1 minute, the average volume of foam produced at pH 9 was larger than those at pH 7, not supporting the hypothesis.

The data trend supported previous research (Creative Enzymes, 2022) as when the pH level is lower than optimal, enzymatic activity occurs slower, as the pH value has deviated from the ideal conditions. While Table One displays the average foam produced after 2 minutes at pH 3 is 75.38mL, the volume for pH 5, 7 and 9 is over 20 mL higher. Due to their protein nature, enzymes are very sensitive to changes in their environment, thus even a slight deviation from the optimal environment may alter the enzyme’s structure or decrease the affinity to the substrate; therefore significantly decreasing the rate of reaction (Creative Enzymes, 2022). Graphs One and Two reinforce this, as at pH 11, the data values decrease by 97% in some groups, thus indicating that the environment is no longer optimal for enzyme activity. 

While the experimental results are consistent with scientific literature (Gillespie 2018; Creative Enzymes 2022) regarding the relationship between pH level and catalase activity, this was inconsistent across the eight experimental groups. Graphs One and Two contain significant scatter, with some precise data values. The most evident source of scatter is the outliers displayed in Graph Two, which exceed other data values by over 20mL. The largest evidence of scatter showed a 52mL difference between the minimum and maximum values at pH 7, displayed on Graph One. These anomalies impacted the upwards trend of the data, potentially limiting reflecting the true value of catalase (Gillespie, 2018), and overall preventing reliability within the investigation.

DISCUSSION: Errors

During this investigation, eight groups were used as samples. Having a larger sample size is imperative for a valid test, as it reduces the impact of random errors, which produce outliers. Table Two and Graphs One and Two displayed outliers, which would be minimised if further testing took place, by producing more averages, therefore, ensuring more valid results.

The disparity within the size of the liver cubes is a significant source of random error that can account for a substantial amount of the scatter. This was inconsistent, as one of the experimental groups, group six, produced cubes of significantly lower mass. As evident in Table Two, at pH 3, group six’s cube was 0.91g, being 0.81g lighter than the largest cube of 1.74mg. The mass of group six’s cubes was consistently lower, as highlighted in Table Two, followed by the data values in, Graphs One and Two. These anomalies are due to the cubes with a larger mass having a larger Surface Area/Volume ratio. Moreover, the larger the exposure that the substrate has to the enzyme, which comes with a larger surface area, the faster the reaction occurs (BBC, 2022).  

Further contributing to this ratio is the procedures of weighing the cube. After being weighed, the cube was left exposed on paper towel, with water concentration slowly reducing, along with the mass and surface area. While this cannot be physically proven through the data, it can be inferred that as the surface area decreased, so did the rate of diffusion and catalase activity, thus impacting the reliability of the data. Another potential source of error could be the size of the drop of detergent added to the measuring cylinder. The larger the amount, the more foam that can be produced, which would make the results invalid in relation to the rate of oxygen production and true value of catalase. In order to minimise the impact of these errors, more resolute measuring apparatus and procedures must be used. Machinery must be used to keep the size of the cube consistent, as it cannot be done by a human.

The true value of catalase, pH 7 to 11, was identified through previous studies (Gillespie 2018; Science Buddies 2012), which was reinforced through the experiment, therefore displaying validity in the data, yet limited reliability. While outliers were present, not all values consistently differed from the true value; therefore, it is unlikely that the experiment was subject to systematic error. However, there is potential that the calibration of scales for group six had been faulted, but could not be considered systematic as it didn’t affect all samples consistently. The stock solutions of hydrogen peroxide may present as an error.  If these batches were made with an incorrect ratio of substrate, labelled incorrectly, stored at different temperatures, or made at varying times, this would be considered an error and create invalid results. It is necessary to repeat the experiment with new apparatus and fresh solutions so as to identify the presence of systematic error and verify results by observing whether the data differs by a consistent margin.

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