Determine Atomic Size Lab

Introduction:

This experiment's purpose is to calculate small values (molecular and atomic size) in different phases, such as a gas, liquid, and solid by using practical methods. If the molar mass is known, one can estimate the atomic size through practical measuring techniques with little experimental error. This experiment consists of measuring a block of a solid element (Copper and Zinc), measuring the volume of the lead pellets, and measuring the amount of carbon dioxide gas in a balloon. These experiments will allow one to estimate the atomic or molecular size by using doable measurements and calculations.

Experimental Procedure:

Found the mass of a cylinder of Copper and the mass of a cylinder of Zinc on an electric scale, recorded

in Table 2.
Measured the volume of both metals (separately) by adding 15.0 ml of water into a 25 ml graduated cylinder that contained each metal, recorded in Table 2.
Found the density of each metal, recorded in Table 2.
Filled a 10 ml graduated cylinder with 10 ml of lead shots. Measured how much water it took to fill the graduated cylinder up to the lead shots, by using a buret.
By pouring the water out and finding the empty space in between the lead shots the packing coefficient was found.
Weighed a 25 ml graduated cylinder.

Added 20 ml of water and weighed the graduated cylinder again.

Measured the diameter and length of the spherical dry ice using a tape measurer.

Measured the mass of the dry ice on the electric scale.

Placed the dry ice into a flask, covered the opening of the flask with a balloon, and placed tape around the balloon in order for the carbon dioxide gas not be able to leak.

Waited for 40 minutes for the dry ice to turn into carbon dioxide, then measured the circumference of the balloon to figure out the diameter and volume of the balloon.

Discussion:

When finding the atomic size for the cubic and spherical atomic model, I found that the experimental error percentages were not far off. There was more of a percentage error for Copper due to random errors when calculating the cubical atomic model, since the cylinder was only weighed once. This cause would also be accurate for the other cubical model of Zinc and both the Copper and Zinc spherical atomic models. If the cylinders were weighed multiple times and an average was taken, then the experimental errors may have decreased due to finding the closer actual value. Both of the spherical atomic models were closer to the actual atomic diameters than when compared to the cubical model. This is because the empty space between the atoms are taken into account. Both experimental values of Copper and Zinc were relatively close to the actual value, but random errors or human errors--measuring the solid cylinders inaccurately and producing an inaccurate packing coefficient when measuring the volume of water poured into the lead pellets--will have thrown these measurements off. By these measurements being off, it lead to experimental

errors.
The experimental error of the molecular size of water was most likely due to random error. It is not difficult to find the density of water when given the mass of the water sample and the volume of the water sample. The random error could have been due to the volume of the water being above or below the 20 ml line or not weighing the water sample multiple times, then taking the average to get a more accurate answer. The experimental value was close to the actual data, depicting a closely accurate molecular size of a water molecule.
When calculating the parameters of the dry ice sample, the experimental value was off, most likely due to human error. This may be due to measuring the dry ice sample incorrectly and having the ice wait too long on the scale. As the carbon dioxide escaped from the dry ice, it became smaller, making the calculations wrong and having an experimental error of 23.65%. Although we concluded with this error, our experimental size was not far off from the actual. It was found that the carbon dioxide atoms do not take up a lot of space in its gaseous state--gas is mostly empty space. The experimental percentage of empty space that we calculated was 99.90%.

Conclusion:
This experiment measures atomic size in different phases such as a solid, liquid, or gas by using doable practical methods such as measuring solids using a tape measurer, and gas through an inflated balloon. The data from the experiment shows that both liquids and solids are not made up of atoms, but are made up of mostly empty space (by putting the spherical solids into a graduated cylinder and then pouring water in). Although atoms are close to each other in either a solid or liquid form, atoms have an extensive amount of empty space around them. Through the dry ice experiment, it shows that gases have even more empty space around them. By completing this experiment one can conclude that the atomic size can be found using practical methods when knowing the atomic mass and that in a solid, liquid, or gas matter, a large amount is filled by empty space.