# Measurement Of The Physical Properties Of Matter Biology Essay

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Science is a systematic enterprise that gathers knowledge about our universe and which organizes knowledge into testable experiments, theories and laws. In simpler words, science is "knowledge attained through study and practice" (Science Made Simple, 2006). This means that theory and hypotheses are tested by scientists in an effort to end up in generalizations, which if replicated by others will have same results. Measuring instruments, such as the thermometer, the ruler or the scale, are means used by scientists to perform their experiments in order to determine the dimension, quantity or extent of something. Measurements are defined usually in comparison to a specific unit, such as meters, Celsius degrees or kilos, and are used to express magnitudes of physical quantities.

The purpose of the below experiment deals with the understanding of mass, volume and density, their properties and usefulness as well as ways of measurement. More specifically, comparisons between small samples of liquid and solid in relation to their density and their percentage errors are tested, while being compared with literature values. Moreover, predictions regarding the reactions of two immiscible liquids (mixes of olive oil, alcohol, and pure water) are examined. Finally, an explanation on the difference between solid and liquid water is made by giving special attention in its importance for life; examples of physical phenomena on Earth are discussed.

Defining the basic properties discussed in this paper, mass, volume and density, will ensure readers to have a same understanding of these concepts:

Mass is a fundamental property of an object that measures its quantity of matter usually in kilogram units (kg), which can be measured with the use of a balance

Volume is the quantity of space occupied by a solid, liquid or gas, usually expressed in units of cubic meters (m3), litters (L) etc

Density is a substance's physical property that compares the mass of an object for a specific volume. In other words, density is the ratio of mass to volume (g/cm3)

## Materials and Procedure:

The experiments took place in the labs of the Deree - The American College of Greece during the Fall Semester 2012. The activities were completed within two lab activity hours on September 24th and October 1st, where the density of solids and liquids was examined and the mixture of liquids was tested, respectively.

The essential material and equipment necessary for the study and completion of the experiments are:

Different samples of metals (copper, iron, aluminum)

Different liquids (pure water, alcohol, olive oil)

Triple beam balances (or electronic balance)

Three 100-mL beakers

Calculator

Hydrometer / Densitometer

## Examination of Density of Solids

In order for someone to carry out this experiment three different solids have to be obtained (in this experiment copper, iron and aluminum are used). Using a triple beam balance or an electronic balance, measure and record the masses of each metal. Next, measure their volume by following the next steps:

Place 75-80mL of water in a 100mL-graduated cylinder (or 18-20mL in a 25mL-graduated cylinder) and measure with exact precision the water's volume (V1)

Carefully immerse the metal in the water and record the volume shown in the cylinder (V2)

Calculate the volume of the metal by subtracting from the total volume of the water and the metal, the volume of the metal (V= V1 - V2)

The above measurements are performed twice for each metal by using different pieces of the same metal each time. After doing so, the density of the three metals used is determined by dividing the metal's mass with its volume (). Now, the average density of each metal is calculated with the use of the two measurements found above for each metal. After comparing the average density with the literature values for the density that will identify the metals used, the percentage error should be calculated with the use of the following formula:

Percentage Error = Average Density - Density from Literature Ã- 100 (%)

Density from Literature

## Examination of Density of Liquids

In order for someone to carry out this experiment three different liquids have to be obtained (in this experiment pure water, alcohol and olive oil are used). Using a triple beam balance or an electronic balance:

Measure a graduated cylinder of 25mL (or 100mL) (m1)

Place 15 - 25mL of one of the liquids in the cylinder and record the exact volume of this liquid

Measure the mass of the cylinder in the presence of the liquid (m2)

Calculate the mass of the liquid by subtracting from the total mass of the cylinder and the liquid, the mass of the cylinder (m= m2 - m1)

The above measurements are performed twice for each liquid by using different volumes of the same liquid each time (it is important during the experiment, to wash and dry the cylinder when putting a new liquid in it). Then, determine the density of each of the liquids by dividing the mass of the liquid with its volume (d= m/V). After doing so, the average density for each of the three liquids is calculated and then with reference to the density tables (found on the Internet) identification of the unknown liquids is carried out. Finally, the percentage error has to be calculated with the use of the above formula:

Percentage Error = Average Density - Density from Literature Ã- 100 (%)

Density from Literature

## Examination of Mixing Two Different Liquids

In order for someone to carry out this experiment pure water, alcohol and olive oil have to be obtained. Using three 100-mL beakers place:

About 10mL of distilled water and 10mL of olive oil in the first one

About 10mL of distilled water and 10mL of alcohol in the second one

About 10mL of alcohol and 10mL of olive oil in the third one

After doing so, shake all three mixtures, observe how liquids interact and record your observations.

## Measurement of Density Using a Hydrometer

In order for someone to carry out this experiment pure water and another unknown liquid have to be obtained. Put a certain amount of water in a 100mL graduated cylinder and place the hydrometer in the cylinder; measure and record the density of the water. Repeat the same procedure for the unknown liquid.

## Examination of Density of Solids

Table 1

Table 2

Table 3

Average Masses of Metals

Average Density of Metals

Graph Graph

## Examination of Density of Liquids

Table 4

Table 5

Table 6

Average Masses of Liquids

Average Density of Liquids

Graph Graph

Graph

## Comparison of Solids

Among the solids studied in the experiment (copper, iron, aluminum), copper has the higher density reaching an average of 8, 9365 gr/mL, followed then by iron with a lower density of 7, 18 gr/mL and aluminum with 2,701 gr/mL (Graph 1). It is observed that, even if the metals' volumes are almost the same (â‰ˆ18 mL), their density is proportional to their masses; in other words, the bigger the mass the higher the density (Graph 2).

A difference in the values of the density is observed when comparing them with the density from literature values. This deviation is a result of experimental errors probably resulting from the way the experiment was conducted. The percentage error when examining cooper and aluminum is almost nil, while in the case of iron an error of 8,744% is detected (Table 2), this leading to a divergence of 0, 688 gr/mL (Table 3). Possible reasons are the imprecise measurement in the cylinder's scale or the immersion of the cord from which the metal hangs (the density of the cord was also measured).

Density is an effective way to check the purity of metals, especially when referring to precious metals like gold. The principle "the higher the density the purer the metal" applies here. If the density of a gold object is less than 19, 3 gr/mL, this being the density of gold, it means that any number of metals of lesser value alloyed has been mixed with the sample.

In order to conclude to the above results, measurements from two samples for each metal were taken. The discrepancy among the samples is very small; the difference in the masses affects the volume of the metals by a few decimals (Table 2), which consequently influences also their density. Only the measurements of iron samples have a larger variation; a difference of 15, 9 gr in the masses resulted in same volumes but in different densities. More specifically, a divergence of 0,884 gr/mL is observed, which "defines" directly the high percentage error.

## Comparison of Liquids

Among the liquids studied in the experiment (pure water, alcohol, olive oil), water has the higher density reaching an average of 0, 9525 gr/mL, followed then by the olive oil, the liquid with the lower mass (Graph 4), with a lower density of 0, 874 gr/mL. Even if alcohol has a larger mass compared to olive oil, it has the lighter density among the examined liquids, which amounts to 0, 7615 gr/mL (Graph 3).

When comparing the density of the liquids examined with the density from literature values, a deviation is observed. This divergence is a result of experimental errors, either these being in the control of the experimenter or not. Errors may have been caused due to the way of conducting the experiment, this leading to a divergence of 0, 0475 gr/mL on the density of water, 0, 0285 gr/mL on the density of alcohol and 0,026 gr/mL on the density of olive oil (Table 6). But even this small difference of decimals, the numbers are so close that results are reproducible and the experiment effective.

When mixing these liquids with one another, the difference in their densities is confirmed:

Water and olive oil are immiscible; when these liquids are mixed it is observed that oil floats on water and is accumulated in the surface of the beaker. Examples in our everyday life are the crude oil floating on the sea after a spill or the olive oil that separates out in salad dressing

Water and alcohol, when mixed, a homogeneous mixture is created

Finally, when olive oil and alcohol are blended, the lighter density of alcohol makes it float on oil

It is important to note that oil is a non-polar liquid unlike water and alcohol, which means that oil molecules have no charge and consequently are not attracted by water or alcohol molecules (Elvidge, 2012). The homogeneous mixture created by water and ethanol results from the attraction of their molecules; the low density of ethanol makes its molecules fall between the spaces left by water.

## Comparison of Solids and Liquids in Relation to Density

From the above experiments, it is observed that solids are much denser in relation to the liquids examined. This is easy to understand from density's formula (d= m/V); the lower the volume the larger the density. It is important to mention that this is not a generalization; some solids are denser from liquids and others are lighter.

## Phenomena from our everyday life

Ice floats

Solid water (ice), unlike other substances, has a lower density when compared to liquid water. Therefore ice when being in the water floats upon liquid water and do not sink. This is explained to the increased number of hydrogen bonds per water molecule contained in the ice in relation to the liquid water; the more the hydrogen bonds the more the structure. In solid water's case this results in more unoccupied space between the water molecules, due to the arrangement of the crystal lattice created, or in other words to lower density upon unfreezing (McElroy, 2002).

Significance of the water's density for the existence of life

Water possesses certain properties that are very important for the existence of life on Earth. These properties, as Martin Chaplin argues, are "brought about by the hydrogen-bonded environment particularly evident in liquid water". The way water molecules interact is very important; strengthening or weakening the hydrogen bond in water can have severe consequences. According to studies, if the density of water changes, water would not be liquid in the surface of Earth something affecting, for example, water ionization (Chaplin, 2012). If the density of ice became greater than this of the liquid water, ice would sink this affecting lakes and ponds which would freeze from the bottom up, something impacting life on Earth.

Air rises when heated

When air is heated its density is lighter in relation to cooler air; in other words molecules in heater gases move faster by bumping into each other. As temperature increases, molecules move faster and the number of collisions become more violent, something that forces them to expand by creating more space between them. Air, in that way, rises through denser air until it reaches a level of equal density where it then "floats" (Hot Air Rising, 1991).

Airships and balloons containing gas helium

Helium is a non-inflammable and non-explosive gas, possessing a unique combination of properties. Its lifting power, due to its very light density, is the reason why it is extensively used for airships and balloons. Helium gas has lower density than air and as a result, it allows the balloon and the airships to rise when immersed in it.

## Usefulness of a Hydrometer and its Limitations

The hydrometer is an instrument used for the measurement of the density of liquids. It is very easy in its use, as the only thing the experimenter has to do is to place the hydrometer in the tall container/cylinder in which a liquid is poured. The scale contained inside the stem facilitates the measurement.

## Conclusion and Remarks

The examination of liquids and solids in the above experiment, give a clear understanding of their properties, the way of their measurement (mass, volume and density) as well as how they interact with each other. The experiments provide a clearer understanding of the significance of density for life on Earth. More specifically a clearer understanding of the above elements is achieved:

Importance of mass, volume and density

How solids and liquids are measured and how they differ

How percentage errors are calculated and how they are interpreted

Usefulness of density measurements

How two immiscible liquids behave when mixed