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This laboratory experiment focuses on the proper use and handling of an analytical balance for precise mass measurement. It involves determining the mass of five 5-centavo coins using both individual weighing and weighing by difference methods. The experiment analyzes the accuracy and consistency of these methods, highlighting the importance of precision in scientific measurements and the impact of factors like wear and tear on coin mass. It also emphasizes the need for careful handling and calibration of analytical balances to ensure reliable results.
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Experiment No. 1 Using the Analytical Balance
I. Objectives ● To learn, use, and handle the analytical balance properly for precise measurement. ● To determine the mass of each five (5) centavo coin. ● To understand the significance of using the analytical balance in the laboratory.
II. Materials and Apparatuses ● Sponge ● Petri dish ● Tweezers ● Oven ● Desiccator ● Analytical balance ● Wash bottle
III. Preparation of Reagents/Samples
IV. Methods and Procedures
V. Illustrations and Set-Up
Description: Weighing by difference is a method used to determine the mass of an object by measuring the mass before and after adding or removing that object. In this case, the technique involves using 5 centavo coins. The process begins by placing an empty petri dish on an analytical balance and recording its mass. Next, a specified number of 5 centavo coins is gradually added to the petri dish, and the new mass of the petri dish with the coins is recorded. To find the difference in mass of the coins, the initial (larger)
dish with the coins, yielding the total mass of the coins added.
The provided data shows that when 5 coins are included, the total mass recorded is 10.9429 grams, but the mass calculated by difference is only 2.2017 grams. For 4 coins, the total mass recorded is 8.7412 grams, while the mass calculated by difference is 2.1815 grams. This trend continues down to the measurement for 1 coin, where the total mass recorded stands at 2.1960 grams, with the mass by difference also noted as 2.1960 grams. Weighing by difference is an effective technique for accurately assessing the mass of individual items like coins, as it utilizes the precision of a balance scale and reduces the impact of environmental factors. Although this method is dependable, it necessitates careful attention to detail to ensure accurate outcomes.
Table 3. Comparison between weighing individually and weighing by difference
Coin Individual Mass (g) Mass by Difference (g) Percent Difference (%) 1 2.2016 2.2017 -0. 2 2.1818 2.1815 0. 3 2.1641 2.1649 -0. 4 2.1997 2.1988 0. 5 2.1966 2.1960 0. Average 2.18876 2.18858 0.
Calculations:
Coin 3's Individual mass is 2.1641, please change it on your lab manual
Description: The comparison between weighing individually and weighing by difference provides insights into the accuracy and consistency of these two methods for determining the mass of 5 centavo coins. Each coin's mass is individually measured in separate weighings, resulting in a specific value for each coin. For instance, the first coin has an individual mass of 2.2016 grams, while the second coin measures 2. grams, and so on, with the masses varying slightly for each coin.
The weighing by difference method starts by measuring the overall mass of a collection of coins. From this total, the mass of each coin is determined by finding the differences noted. To calculate the percent difference, you take the mass of each coin, subtract it from the mass calculated by difference, divide that result by the original mass of the coin, and then multiply by 100. For each coin, it illustrates the small discrepancies between the two methods, ranging from -0.0045% to 0.014%, with an average percent difference of only 0.008%. This slight variation demonstrates that both methods produce comparable results, reinforcing the assertion that weighing by difference is a highly effective alternative to individual weighing. This approach is particularly advantageous in scenarios where time and efficiency are important. This comparison emphasizes the precision of both techniques while demonstrating that weighing by difference can serve as a practical method for determining mass with high accuracy.
VIII. Conclusions
Using five 5-centavo coins as the main test samples, the experiment was effective in showing how to use the analytical balance correctly for accurate mass measurement. Despite strict quality control measures to guarantee consistency and unity in both the size and weight before circulation, the experiment found slight differences in the masses of these coins. Despite the little differences, the measured and observed weights, which varied from 2.1641g to 2.2016g, can be detected using a sensitive analytical balance. Both the individual weighing method and the weighing-by-difference method produced findings with negligible percent variations, demonstrating the precision and dependability of both techniques in calculating mass.
There are a number of reasons for the observed variations in mass. One explanation is the actual manufacturing process, where small differences in material distribution or precision cutting during production can cause subtle weight alterations between coins even under careful tolerances. These could result from differences in the coin's thickness, an uneven application of plating material, or even flaws in the minting molds. Additionally, because coins are subjected to friction, scratches, and corrosion over time, wear and tear from circulation also plays a big part. Handling by multiple people, exposure to environmental elements, and physical damage could all contribute to small losses in material, which would decrease the coin’s mass.
Another critical factor is residual surface contaminants, such as oil, dust, or moisture, which may not have been fully removed during the weighing process. Despite cleaning the coins thoroughly and even using desiccators to minimize these influences, trace amounts of residue can still attach to the coin’s surface, adding to its weight. For instance, during the experiment, some coins displayed visible scratches and black spots, indicating they had experienced physical and environmental wear that likely contributed to the variation in their masses. Overall, the experiment showed how to properly use the analytical balance to compute the mass of individual coins, finding their differences and their percentages. It demonstrated how crucial accuracy is in scientific measurements and how analytical balances can reliably pick up even minute changes.
