When measuring the density of irregular objects, a method to determine this measurement is by reading the change of liquid level when the solid is inserted in a volumetric container. In this experiment, metal pellets were used as the sample of irregular solids. The first step in the process to determine the density is the requirement to measure the mass of the solids. Secondly, noting the initial water level, the solids must be inserted into the volumetric container that holds the water. Once the final water level is determined, it is possible to conclude with the density measurement. Knowing that density is the mass of the object divided by the volume, in this case the change in water level, the density can be determined.
Like the density determinations of solids, liquids require the knowledge of the measurement of volume and mass in order to determine the density. Granted that the water is contained in volumetric glassware, only the mass needs to be determined. Determining the mass of a liquid is done by weighing the empty cylinder, and then the cylinder with the liquid, and finding the difference. Using the same formula that density is equivalent to the mass of the liquid divided by its volume, the density can then be determined. However, it is also possible to determine the density of the liquid by knowing the temperature of it. At or around room temperature, the density of water can be determined because the temperature has a direct effect on the density of the liquid.
Finally, the density of solutions was studied. By adding different percentages of sodium chloride to water, it was possible to compare the densities of the samples. The density of the solutions, in this case, was determined by dividing the mass of the solution by the volume. By theory, the density of the solutions should increase as the percentage of salt is higher. However, this must be executed very accurately to achieve perfect results.
Results
Data Table 1. Density of Solids – Sticky Notes
Data Table 2. Density of Solids – Metal Pellets
Data Table 3. Density of Pure Liquids – Water
Data Table 4. Density of Pure Liquids – Unknown Liquid
Data Table 5. Density of Solutions – Water and Salt
Error Analysis
When determining the density of a liquid, the measure of both mass and volume need to be very accurate in order to attain a precise measure of density. During the experiment, it is seen that the density of water is slightly miscalculated according to the handbook density. Knowing that as volume rises, density lowers, the mistake probably lies in the measurement of the liquid’s volume. If the result of the volume had been slightly lower, then the calculation would have been more accurate compared to the handbook density.
When measuring the density of solutions, it is very important to measure carefully and precisely. In theory, the higher the percentage of a sample is in a liquid, the higher its density should be. Though the table’s calculations did somewhat follow a general lower-to-higher density measurement as the percentage increased, the measurements had been wrong in some spots. The largest variation occurred in the sample with 20%. However, it was noted that some of the water was spilled as the salt was dissolving, resulting in a higher density.
Discussion
In this experiment, we learned the process of determining density, as well as the effect that density has in chemistry. By experimenting with both regular and irregular solids, pure liquids, and mixed solutions, it was found that density is the measurement of how close the molecules of that substance are. The closer they are, the higher the density. This was found when comparing the densities of the solids and the liquids. Though it is common knowledge that solids are denser than liquids, the results had shown evidence that the densities between both states are considerably different –due to the composition of the molecules within.
There was also evidence that temperature is an important factor when measuring the density of liquids. According to the data in the handbook, the density of a liquid seems to increase as the substance becomes warmer. Knowing that molecules are more active when they are exposed to higher temperatures, it is evident that these molecules use up more space within the substance. Therefore, temperature has a direct effect on the determination of densities of liquids. However, water does not follow this rule, because it expands with temperature. For this reason, ice can float in water, unlike most other substances, in which the solid state cannot float in the liquid state.
In this experiment, I have not only evaluated my understanding of density, I have also witnessed its effect in chemistry with different substances and objects in different states. Through the experimentation, I am also able to apply density to real-life occurrences. For example, from what I learned during the segment where salt was used together with water to determine the effect on density, I was able to find the meaning of this process in nature. In the sea, it is much saltier as the depth of the water increases. This is because salt water is denser than pure water, so it sinks beneath the less dense water. Also, I have realized the reasoning behind the idea that saltier waters result in easier floating. Since the density of such waters is higher, lighter objects are pushed above the denser liquid. Through density, it is evident how chemicals exist in the universe –from how they change states, to how they arrange themselves in the seas.
Questions
What error would be introduced into the determination of the density of the regularly shaped solid if the solid were hollow? Would the apparent volume of the solid be larger or smaller than the actual volume? Would the density calculated be too high or too low?
If the solid being measured were hollow, using a regular density formula is not possible. The density formula calls to find the mass divided by the volume. However, if a solid is hollow, then the space within is not composed of solid material. The volume calculated, in that case, could not be correct. It would be too high, since the volume formula measures within the solid. As a result, the density of the solid would be too low, since the density of a solid decreases as the volume becomes higher.
What error would be introduced into the determination of the density of the irregularly shaped metal pellets if you had not stirred/shaken the pellets to remove the adhering air bubbles? Would the density be too high or too low?
If air bubbles had remained on the pellets, the resulting density calculation would have been slightly too high. This is because the air bubbles would have taken up more volume, resulting in a greater change in water level. This greater change in water level results in a density that is too high.
Your data for the density of sodium chloride solutions should have produced a straight line when plotted. How could this plot be used to determine the density of any concentration of sodium chloride solution?
The plot could be used because if the mass of the sodium chloride is recorded, then this set amount can be used in the formula for any given volume of substance in the solution. As the volume of the water increases, the density decreases. As the mass of salt added increases, then the density increases. In this case, if the same amounts of salt were added to any set of water volumes, the line should still be plotted in the same direction.
What is the difference between the density of a solution and its specific gravity?
Density is the volume a substance or object has per its mass. However, specific gravity is defined as the density of a substance compared to the density of water. The density is a calculated amount using the fact that density is the mass of an object divided by its volume. Specific gravity is the ratio of density of the substance to the density of water. The resulting density measures are values of dimension defined by units –the measure of specific values do not denote dimension, but rather its relation to water.
