Ex 5 Rekative Density.docx

Experiment 5: Relative Density Laboratory Report Andrea Benavidez, Kimiko Beltran, Rachel Cajiles, Ralph Canivel Department of Math and Physics College of Science, University of Santo Tomas España, Manila Philippines Abstract This experiment determines the components of substances with different densities. Three activities were done in this experiment. The first one was to know and compare the density of a specific cylinder as compared to the standard one by knowing the volume and weight of the cylinder provided and computing for its percent error. The volume of 7 ml and the weight of 16.57 g was used to determine the density which was 2.37 g/cc. The percent error obtained was 12.22%. The second activity was to know the density of the bone. The weight of the bone in air, 75g, and in water, 50g, was determined. These measurements were used to know the density of bone which was 3 g/cc. The third experiment was to know the density of a regular soft drink and density of a diet soft drink using a pycnometer. The densities obtained were 1.008 g/cc and 1.00 g/cc, respectively. Introduction Density is a characteristic property of a substance. It is the relationship between the mass of the substance and its volume. It degree of compactness of a substance. The atomic mass, size, and arrangement determines the density of a substance. It is obtained by dividing the mass of a substance over its volume. Objects with similar volume but different masses have different densities. To determine the density of a liquid or powder, one must use a pycnometer. Relative density is defined as the ratio of density of a standard substance to the

density of a sample substance under specified conditions. Water was usually the one used as the standard substance. The density of water is 1 g/ml. to determine the density of a liquid by using a pycnometer, and to determine the density of a substance by Archimedes Principle. Theory Relative density can be defined as the ratio of the density of one substance to that of a reference substance – in the case where water is used as a reference substance, the term specific gravity is used to refer to this ratio. In this experiment, the relative density of a bone was computed through the use of the following formula: R.D. = 𝑾

𝑾𝑨 𝑨 −𝑾𝑾

Where WA is weight of the bone in air, and WW is the weight of the bone in water. The bone’s relative density was then used to compute for its density using the following formula: density of bone = (R.D.) * density of water In another part of the experiment, the relative density of regular soft drink and diet softdrink was computed through the use of the following formulas: 𝑾 −𝑾

R.D. of regular soft drink = 𝑾 𝑹 −𝑾𝒑 𝑾

𝑷

𝑾 −𝑾

R.D. of diet softdrink = 𝑾 𝑫 −𝑾𝑷 𝑾

𝑷

Where WP is the weight of an empty pycnometer,

The density of the bone was solved also using the formula:

WW is the weight of a pycnometer filled with water,

𝒅𝒆𝒏𝒔𝒊𝒕𝒚 𝒐𝒇 𝒃𝒐𝒏𝒆 = 𝑹. 𝑫. 𝒙 𝒅𝒆𝒏𝒔𝒊𝒕𝒚 𝒐𝒇 𝒘𝒂𝒕𝒆𝒓

WR is the weight of a pycnometer filled with regular soft drink,

In activity 3, the weight of empty pycnometer (Wp), weight of pycnometer filled with water (Ww), weight of pycnometer filled with regular soft drink (Wr) and the weight of pycnometer filled with diet soft drink (Wl) were determined. The relative density of regular soft drink and light soft drink was solved using the formula:

and WD is the weight of a pycnometer filled with diet soft drink.

Methodology In this experiment, the materials used are: spring scale, graduated cylinder, beaker, cylinder, bone from pig`s or cow`s leg, regular and coke zero (diet) soft drinks and pycnometer. In activity 1, a cylinder was weighed using the digital beam balance. In a graduated cylinder, a small amount of water was placed as its initial level was noted exactly as possible. The cylinder was placed inside the graduated cylinder and due to impenetrability, the cylinder displaced the volume of the water equal to their volume and the new level of water was noted. The volume of the cylinder was determined as its volume is the difference between the two levels of water. And also, the density of the cylinder was determined. In activity 2, the bone was weighed in air and recorded it as WA. A piece of thread was tied to the bone and it was immersed in a beaker of water wherein the bone immersed in water was weighed and recorded as WW. The relative density of the bone was computed by using the formula: 𝑹. 𝑫. =

𝑾𝑨 𝑾𝑨 − 𝑾𝑾

𝑅. 𝐷. 𝑜𝑓 𝑟𝑒𝑔𝑢𝑙𝑎𝑟 𝑠𝑜𝑓𝑡 𝑑𝑟𝑖𝑛𝑘 = 𝑅. 𝐷. 𝑜𝑓 𝑑𝑖𝑒𝑡 𝑠𝑜𝑓𝑡 𝑑𝑟𝑖𝑛𝑘 =

𝑊𝑟 − 𝑊𝑝

𝑊𝑤− 𝑊𝑝 𝑊𝑙 − 𝑊𝑝

𝑊𝑤− 𝑊𝑝

Also, the density of regular and diet soft drinks was solved. Results and Discussion Table 1: Relative Density of Cylinder Activity One Weight of cylinder (g) Initial Level of Water (mL) Final Level of Water (mL) Volume of Cylinder (mL) Density of Cylinder (g/mL) % error Accepted Value (g/mL)

16.57 60 67 7 2.37 12.22 2.7

In Table 1, the volume of the cylinder can be solved by making use of a graduated cylinder and the displacement of its volume once the cylinder is placed within. The cylinder used by the students was an Aluminum and had an accepted value for density of 2.7g/mL whereas based on experiments the students produced 2.37g/mL with a percent error of 12.22%. The error may be brought about by the method of gaining the data and the way the density was solved.

Table 2: Relative Density of Bone Activity 2 Weight of Bone (air) (g)

75

Weight of Bone (water) (g)

50

Rel. Density of Bone

3

Density of Bone (g/mL)

3

Finding

Figure 1. Diet coke and Regular coke respectively floats in a water

Osteopetrosis

Table 2, describes the density of a given to the students by the Laboratory instructors. This experiment tests if the bone given has a given condition of either osteoporosis, osteopetrosis, or osteopenia. Based on the formulas and solution said above, the finding of the students is that their given bone has Osteopetrosis which is more than 1 standard deviation from the mean. The density of the said bone is 3 g/mL. Table 3: Relative Density of Coke and Diet Coke Activity Three Weight of empty pycnometer (g) Weight of pycnometer with water (g) Weight of pycnometer with reg coke (g) Weight of pycnometer with diet coke (g) Rel. Density of reg. coke Density of reg. coke (g/mL) Rel. Density of diet coke Density of diet coke (g/mL)

14.99 40.24 40.44 40.19 1.008 1.008 1.00 1.00

The last table is to test the relative densities of coke and diet coke. The density of coke based on the formula is 1.008 g/ml whereas diet coke on the other hand has a density of 1.00 g/mL which makes diet coke lighter by .008 g/mL as you can see on figure 1. Based on these findings it can be inferred that diet coke is indeed “lighter” than regular coke products.

Conclusion The first activity was performed to determine the composition of a substance based on its density. The result of this activity was the density of the cylinder was computed to be 2.37g/cc. It was compared to the standard densities given by the professor and it was determined that the composition of the cylinder was aluminum. In the second activity, the relative density of a bone was calculated by dividing the weight in air of the bone by the weight in water subtracted to the weight in air of the bone. The relative density obtained was 3.00g/cc and with this, the group concluded that the bone has osteopetrosis since it has a higher ISD than the normal bone density. The third experiment was performed to

determine who has a greater density, the regular soft drink or the diet soft drink. This experiment was done using a pycnometer. The densities of regular soft drink and diet soft drink calculated by the group was 1.008g/cc and 1.00g/cc, respectively. Application 1. How can you distinguish “Fool’s Gold” from pure gold? To distinguish “Fool’s gold” from pure gold, one can place the two sample in water. For “Fool’s gold” will float while the pure gold will sink into the bottom since the density of pure gold is greater than the “Fool’s gold”. 2. The solid sample s used in the experiment are denser than water. How will you determine the density of a solid that is less dense than water? Explain the formula that you will use. We can still use the liquid displacement method in looking for the density of a solid that is less dense than water. Put the solid sample in water then note how much water is displaced by the floating sample. Next is you submerge the solid sample fully under the water. Calculate the relative density of the solid by dividing the density when it is floating by when it is submerged. Since the density of water is 1.00 g/cc, then the relative density is equivalent to the solid.

3. The suitability of a person to donate blood may be tested by placing a drop of his blood in a saline solution of density 1.03g/cc. Is he a suitable donor if the drop of blood sinks? Explain your answer. The normal density of blood is 1.06g/cc. If the blood will sink in the saline solution, that means it has greater density than the saline solution. Thus, he is a suitable blood donor. 4. What is the meaning of the expression “tip of the iceberg”? Is there a physical basis for this? The expression tip of the iceberg means that you are only seeing a small portion of something. The physical basis for this is that the majority of the iceberg is submerged underwater and you are only seeing the tip of it. 5. Normal relative density of urine is from 1.015-1.030. What might be said if during urinalysis, a specific gravity higher than normal is obtained? If someone has a relative density higher than the normal relative density of the urine, it is said that the person is dehydrated. The higher the number, the more dehydrated the person is.

Reference:

American Chemical Society. (2017). What is density? Retrieved October 16, 2017, from http://www.mid dleschool chemistry.com/lessonplans/chapter3/le sson1 Cutnell, J., Johnson, K., Young, D., & Stadler, S. (2015). Physics (10th ed.). Asia: John Wiley & Sons (Asia) Pte Ltd. What is Density? (n.d.). Retrieved April 01, 2018,from oolchemistry .com/lessonplans /chapter3/lesson1