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AP Biology Summer project

By jmorgs95 Oct 13, 2013 1129 Words
Finding Density

Density is defined as mass per unit volume, which can be used to determine the object or

substance observed. Many people use the density of objects to find what it is and how to classify the

object. The object of the lab conducted was to find the density of the substances given and to find what

the unknown liquid and solid were. The process to finding what the unknown solid and liquid were,

was to find the density and to conduct multiple trials so when the density is discovered, it is possible to

compare the density found to another one in order to find the liquid or solid. Through finding the

density of objects and substances, it is possible to find what the subject is that is being searched due to

comparing the density found to the known substance with its density.

Purpose: The main idea behind this experiment was to conduct research on five substances and

liquids and determine their density. The density is calculated by finding the mass and volume then

dividing the volume by the mass. The found density is used to compare and for the unknown solid and

liquid is to make them known and find what they are. Finding the unknowns are done by calculating

their densities and finding what it is by comparing the density to other densities which can be found in

the chemistry text book. In finding the densities it is is possible to compare them to each other and find

the unknown densities of the experiment.

Hypothesis: If the volume of the substance is altered, then the mass will change also.

The independent variable in this case, is the volume because when the volume changes, it will also

change the mass, the dependent variable, which affects the density. That is why taking multiple trials is

convenient because by taking many trials it helps to understand how the different volume affects the

density and how density may change.

Materials list:
1. water
2. prepared Salt Water
3. Unknown Liquid-methanol
4. Copper Cylinder
5. Unknown Metal-zinc
6. Beaker
7. Graduated Cylinder 10 ml and 20 ml
8. Distilled Water Bottle
9. Electronic Balance

Procedure: The funnel and graduated cylinder were taken out of the cabinet and the funnel was

placed in the graduated cylinder. Water was poured into the funnel, measuring 10 ml. Before further

measuring, the beaker was placed onto the the electric balance which measured the mass of the beaker.

Once the water was measured, it was poured into the beaker and placed on the electric balance for

measuring. Once the mass was shown, the total mass was subtracted from the beaker mass, which had

been previously done. After the mass of water was measured, the beaker and graduated cylinder were

rinsed. The rinsing took place every time a liquid was used to measure the mass of. The second trial

was done according to the first but the volume was different, instead of 10 ml, 20 ml was measured.

The Copper cylinder was placed onto the electric balance, measuring the mass and the volume was

found by finding the radius and height then put into the equation, v=(pie)(radius squared)(height).

Following, the unknown solid was placed into a graduated cylinder with 10 ml so see the difference in

the measure the the volume could be conducted. Then the mass was conducted when the same amount

of the solid was placed on the electric balance, finding the mass. The same method was used for the

following trial but with more of the solid, instead of 1 ml, 2 ml were used. The densities were found by

dividing the found volume by the mass, this was done by all of the solids and liquids.

Results:
Table 1
Mass
Volume
Density
water
10.14g
10 ml
1.0 g/ml
salt water
15.92g
10 ml
1.6 g/ml
unknown liquid
12.16g
10 ml
1.2 g/ml
copper cylinder
71.39g
12 cm cubed
5.9 g/cm cubed
unknown solid
3.55g
1 ml
4 g/ml

Table 2
Mass
Volume
Density
water
17.73g
20 ml
.89 g/ml
salt water
21.56g
20 ml
1.1 g/ml
unknown liquid
15.91g
20 ml
.80 g/ml
copper cylinder
19.08g
11 cm cubed
6.4 g/cm cubed
unknown solid
6.35g
2 ml
3 g/ml

Mass
Volume
Density
Aluminum foil
.209g
.077 cm cubed
2.71 g/ cm cubed

Observations: When the measurements were taken, the smell of each liquid was different, the

unknown liquid was noticeable due to its strong pungent smell. With salt water, it was more visual

than anything because the difference between distilled water and salt water were very different because

the salt water was much more cloudy showing that it was similar to water but slightly different. Also

the mass of the unknown solid was very surprising because with the small volume, the mass turned to

be larger even though it has a small size.

Analysis: The unknown liquid was methanol, the actual density was .7914 g/ml which is closer

to the second trial rather than the first. The first calculation was 1.2 g/ml where the first one was .8

g/ml which was close to the actual density. The actual density helped to find the liquid it was. Also the

unknown solid was zinc which has a density of 7.14 g/ml. The density calculated ranged from 3-4

which is far off from the actual density. In finding the unknown solid, assistance was required by the

teacher due to our poor calculations. The reason behind the poor calculations was due to the way the

volume was measured, which was being placed in water which could affect both the mass and the

volume. The density of the water may have affected the mass because they both have different masses,

also the potential that they were in a beaker would have disrupted the precision of the calculation.

The thickness of aluminum foil was calculated by dividing the area of the piece by the volume

which was found by knowing the density and mass.

Equation: T=V/A T=thickness V=volume A=area

T=.077/2.0cm squared
T=.03 cm

Conclusion: Finding the density allows the object or liquid being used to be classified which

may be used to compare densities to each other, whether one sinks or floats, often it is compared to

water because water is a standard and a define liquid used to base calculations off of. The hypothesis

created in the beginning of the lab was true because when the volume changes, the mass does also,

however the density is always the same. The calculations used in the experiment were not exact, which

was because of bad ways of measuring which skewed the results and made it more difficult to find the

actual density or for the unknowns and finding what each was. Through conducting this experiment,

the ways used to measure the volume were the most off which have allowed for knowledge and better

knowing for the following experiment.

Work Cited:

“Density measurements”

Cite This Document

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