Lab report 1 Determining the Density of a Polystyrene Sphere PDF

Preview

Summary

This is lab assignment about Determining the Density of a Polystyrene Sphere...

Description

Lab 1: Determining the Density of a Polystyrene Sphere Abstract The purpose of this lab is how to measure masses and volume to know the density of polystyrene. Density is expression of amount of matter in the material per unit of space occupied m . Where V is volume, m is mass. Therefore, by the material and the equation of density is V the experiment will have 3 parts: determining the volume of sphere, measuring masses and calculating the density according to the value of volume and mass. In part 1, the total length of 10 polystyrene balls are 9.15 cm and from there it is easy to figure out the volume of the polystyrene sphere is 0.4011 cm3. In part 2, by using the balance to weight each ball then repeat other 9 of the spheres. We used Excel the find the average and standard deviation. After all, the average for masses is 0.55303. Finally, for part 3, to find the density we need to find out the mass and volume. We use the volume from part 1 and mass from part 2 to calculate the density and the result is 1.33. According to all the data we have, it easy for us to find the average densities and the standard deviation. Data Table 1 shows all of the number that important. It includes the length of then polystyrene balls, the average of radius, volume of the polystyrene sphere and the mean and standard deviation. Table 1: Volume Data Measurement of volume with ruler 1. Length of polystyrene balls laid out end-to-end 2. The average radius of polystyrene ball based on the above measurement. 3. The volume of the polystyrene sphere in cm3 from the measurement average radius. 4. Calculate the mean and standard deviation for the volume of sphere using five of the tabulated measurements on the board.

9.15 cm 0.46 cm 0.4011 cm3 Mean: 0.4452 SD: 0.00387

Table 2: Measured masses of each ball on the analytical balance (g) Ball 1 0.5375 Ball 6 Ball 2 0.5456 Ball 7 Ball 3 0.5355 Ball 8 Ball 4 0.5160 Ball 9 Ball 5 0.5246 Ball 10 0.53303 Average 0.00844 Standard deviation Average Density of ten polystyrene spheres

0.5355 0.5289 0.5367 0.5299 0.5401

Using your mean mass from Table 2 and your volume estimate from Table 1 to calculate the average density of your ten polystyrene spheres

0.53303 =1.33 g /cm3 0.4011

Table 3: Average Densities of the ten polystyrene balls Your data 1.33 Classmate 3 Classmate 1 1.25 Classmate 4 Classmate 2 1.24 Classmate 5 Average 1.23833 Standard deviation 0.5036

1.19 1.20 1.22

Discussion 1. The measurement of the average mass of the polystyrene ball was more precise than the measurement of the average diameter of the polystyrene ball. The precision will be represented as standard deviation. The uncertainty of measure the average diameter of the polystyrene is higher than the uncertainty of measure the mass because when we measure by ruler it harder to read the line, sometime, the result will be between two visible lines and it can’t label all of the digits exactly like the balance. 2. The precision with which the polystyrene balls are manufacture is less than the uncertainty in the mass from the analytical. According to the table 2: measure masses, the standard deviation is 0.00844 g and the uncertainty in mass from the balance is 0.0001 g. The lower standard deviation has more precision. 3. The average radius is limiting the precision in the overall density determination. Based on the uncertainties in the volume and mass, I can use the ruler to measure each of the ball and that will be diameter and then diameter divided by 2 to find the radius. So, I can improve the precision in my determination of the density of the polystyrene ball. 4. We measured the length of the ten balls positioned end-to-end instead of measuring the diameter of each ball independently because when we measure each ball by ruler, it will be harder to read to little line in the ruler so we only can estimate the numbers. Therefore, when we measure all of the balls, it will give us a better amount of correct result. 5. The average densities of class are 1.238 g/mL, 1.238 – 1.160 = 0.078. The difference between class data and true value is 0.078 g/mL. This is a small number and the densities are close to each other....