2.0 DATA LOGGING
2.1 Engage
Introduction
The
melting point of a solid is temperature at which it changes from a solid to a
liquid. The transition between the solid and the liquid is so sharp for small
samples of a pure substance that melting points can be measured to 0.1°C. The
melting point of solid oxygen, for example, is -218.4°C. The temperature, at
which the reverse happens, a liquid changes to solid, is referred to as the
freezing point. For most substances, melting point and freezing point refer to
the same temperature. However, for certain substances the transition
temperatures are different.
The
melting point of water is 0°C (32°F). The freezing point of water is the same
as the melting point as long as the water contains what is called a nucleating
substance. But in the absence of nucleates water can supercool to -42°C before
freezing. It is difficult, if not impossible, to heat a solid above its melting
point because the heat that enters the solid into a liquid. It is possible,
however, to cool some liquids to temperatures below their freezing points
without forming a solid. When this is
done, the liquid is said to be super cooled. Melting point does not fluctuate
in response to changes pressure.
When
a liquid is heated, it eventually reaches a temperature at which the vapor
pressure is large enough that bubbles form inside the body of the liquid. This
temperature is called the boiling point. Once the liquid starts to boil, the
temperature remains constant until all of the liquid has been converted to a
gas. The normal boiling point of water is 100°C. By definition, liquid boils
when the vapor pressure of the gas escaping from the liquid is equal to the
pressure exerted on the liquid by its surroundings.
The
normal boiling point of water is 100°C because this is the temperature at which
the vapor pressure of water us 760mmHg, or 1 atm. Under normal conditions, when
the pressure of the atmosphere is approximately 760 mmHg, water boils at 100°C.
Liquids often boil in an uneven fashion. They tend to bump when there aren’t
any scratches on the walls of the container where bubbles can form. Bumping is
easily prevented by adding a few boiling chips to the liquid, which provide a
rough surface upon which bubbles can form. When boiling chips are used,
essentially all of the bubbles that rise through the solution form on the
surface of these chips.
Intermolecular
forces are the relatively weak forces between molecules that hold the molecules
together in the solid and liquid phase. Intramolecular forces are the forces
within a molecule. These are the covalent bonds in a molecule and it is
stronger than intermolecular forces.
The
electrostatic attraction between the positive end of one polar molecule and the
negative end of another is the dipole force that act between polar molecules.
Dipole forces are generally weaker than hydrogen bond. Both of these forces are
due to dipole moment in molecules. Hydrogen bond is given a separate name from
dipole forces because hydrogen bonding is a particularly strong dipole force.
London
dispersion forces are accidental-induced dipole forces. Like dipole forces,
London dispersion forces are electrostatic in nature. Dipole forces are the
electrostatic forces between molecules having a permanent dipole. London dispersion
forces are the electrostatic forces between molecules having an accidental or
induced dipole. All covalent molecules (polar and nonpolar) have London
dispersion forces, but only polar molecules (those with permanent dipoles)
exhibit dipole forces. As the size of a molecule increases, the strength of the
London dispersion forces increases. This is because, as the electron cloud
about a molecule gets larger, it is easier for the electrons to be drawn away
from the nucleus. The molecule is said to be more polarizable.
The
observable melting and boiling point of different organic molecules provides an
additional illustration of the effects of noncovalent interactions. The
stronger the noncovalent interactions between molecules, the more energy is
required, in the form of heat, to break them part. Higher melting and boiling
point signify stronger noncovalent intermolecular forces. Consider the boiling
points of increasingly larger hydrocarbons. More carbons mean a greater surface
area possible for hydrophobic interaction, and thus higher boiling points. The strength of intermolecular hydrogen
bonding and dipole-dipole interactions is reflected in higher boiling points
For
the melting points, all of the same principles apply where the stronger
intermolecular interactions result in higher melting points. Ionic compounds,
as expected, usually have very high melting points due to the strength of
ion-ion interactions. The presence of polar and especially hydrogen-bonding
groups on organic compounds generally leads to higher melting points. Molecular
shape, and the ability of a molecule to pack tightly into a crystal lattice,
has a very large effect on melting points.
When
a solid melts to form a liquid, there is generally very little volume change
involved (compared to the volume change in boiling). This is because only
some of the intermolecular forces in the solid are broken in the phase
change. additionally, the solid's packed structure is broken up and this
contributes a large part of the energy needed to melt the material.
Packing energy is largely an entropy feature, where the individual molecules
suddenly have a larger degree of freedom of motion available to them.
This increase in entropy of the system requires that the system absorb energy
from the surroundings. For the reverse phase transition, freezing, the
system becomes more ordered (entropy is lowered) and energy is released to the
surroundings. Thus, while intermolecular forces do play a significant
role in this process, entropy also plays a role.
Because there is some volume change
in the process, there will be a pressure dependence as well as a temperature
dependence. For example, most materials
increase in volume as they melt. If
sufficient pressure is applied to the material, the molecules are forced to
remain packed together even as the temperature is raised past the melting point
as the lower pressure is expected, but, if the pressure is lowered, the molecules may
find themselves melting at a lower temperature as the energy needed to unpack
(increasing the volume) becomes lower.
When the molecules of a liquid break
free of all intermolecular forces and separate from each other, they become
gases. This phase change is called boiling. For this phase
change, there will be a significant effect of the strength of the
intermolecular forces as breaking these constitutes a very large part of the
process. However, entropy changes are also large as the volume change
involved in this phase change are generally quite large. Thus, there will
be a larger effect of pressure on the equilibrium between liquid and gas.
The boiling point is defined as the
temperature at which the vapour pressure of the liquid is equal to the external
pressure. The boiling point, the liquid is actually at equilibrium and is
not noticeably changing phase.
2.2 Empower
Procedure (s) :
1. Connect the sensor to an interface
box linked to the computer as shown in figure below.
2. Place the ice in the beaker and observed
the state of ice.
3. Place the temperature sensor in the
ice.
4. Take reading for every 30 seconds of
time interval until it is boiled.
5. Place Bunsen burner below the beaker
for heating the beaker. Click the start button. Observe any transition process and
the temperature they start to change.
6. Record the data.
7. Plot graph temperature against times.
8. Cool the beaker to the room
temperature. Record the temperature and time taken for it to cool.
9. Record the data.
Result :
Heating
of water
|
Temperature, (oC)
|
Time taken , seconds
|
Phase
|
|
0
|
30
|
Solid-liquid
|
|
0
|
60
|
Solid-liquid
|
|
0
|
90
|
Solid-liquid
|
|
0
|
120
|
Solid-liquid
|
|
30
|
150
|
liquid
|
|
50
|
180
|
liquid
|
|
70
|
210
|
liquid
|
|
100
|
240
|
Liquid
|
|
100
|
270
|
Liquid-gas
|
|
100
|
300
|
Liquid-gas
|
|
100
|
330
|
Liquid-gas
|
|
100
|
360
|
Liquid-gas
|
|
100
|
390
|
Liquid-gas
|
|
100
|
420
|
Liquid-gas
|
|
100
|
450
|
Liquid-gas
|
|
100
|
480
|
Liquid-gas
|
|
120
|
510
|
vapor
|
|
142
|
540
|
vapor
|
|
160
|
570
|
vapor
|
Cooling of water
|
Temperature, oC
|
Time taken , minutes
|
|
89
|
1
|
|
84
|
2
|
|
81
|
3
|
|
80
|
4
|
|
80
|
5
|
|
80
|
6
|
|
80
|
7
|
|
80
|
8
|
|
80
|
9
|
|
80
|
10
|
|
80
|
11
|
|
79
|
12
|
|
77
|
13
|
|
77.5
|
14
|
|
76
|
15
|
|
74
|
16
|
|
70
|
17
|
|
68
|
18
|
The graph of temperature against
time taken for cooling process
Discussion :
· The
melting process is a process where the solid phase changed to liquid phase
under specific pressure. The evaporation
process is a process where the liquid phase is changed to gas or vapors phase.
·
The
substance used is water. The melting point of water is 0 oC and
temperature stay the same as the melting process occurred. When water is
heated, the particles gain energy and move faster as to move away their
positions and begun to vibrate around each other.
· The
temperature during boiling process is constant which 100 oC because
the boiling point of water is 100 oC. When a liquid is heated, the particles
gained energy and tend to moved faster. Some particles in water, which have
enough energy to escape into air to from vapor and this process is known as
evaporation.
·
During
solid phase, the water molecules are vibrated around the point and not free to
move. It is expand, but, in a small value when heat is supplied. This is due to the strong force between the
molecules. The energy in the particles is low.
· During
liquid phase, the water molecules moved in random arrangement but still in
fairly stick together. The energy in the molecules is moderate. During
gas phase, the water molecules moved in fast and randomly. The energy in the
particles in very high. During the cooling
process, the particles loss of energy and they came closer together. As they
collide, they will stick together to form droplets forming a liquid. During
this process, energy in particles is loss due to less energy is needed as they
are cooling.
2.3 Enhance
The state or phase of a given
set of matter can change depending on pressure and temperature conditions,
transitioning to other phases as these conditions change to favor their
existence. For example, solid transitions to liquid with an increase in
temperature which is in melting process. Liquid is transited to gases of
molecule in either boiling or vaporization process
Boiling
|
Nomenclature for
the different phase transitions.
A state of matter is also
characterized by phase transitions. A phase transition
indicates a change in structure and can be recognized by an abrupt change in
properties. A distinct state of matter can be defined as any set of states distinguished from any other
set of states by a phase transition.
Now, in this enhance, this
process can be applied to daily life. There are many examples that related to
transitions process such as melting, freezing, boiling, condensation, steaming
and others.
2.3.1 Application in daily life
2.3.1.1 Boiling for water sterilization
Boiling is the rapid vaporization of liquid, which occurs
when liquid is heated to its boiling point, the temperature at which the vapor
pressure of the liquid is equal to the pressure exerted on the liquid by the
surrounding environmental pressure.
Boiling can be used as a method of water purification but is
only advocated as an emergency water treatment method. As the water is boiled
in high temperature, it is most effective in killing or inactivating most
bacteria, viruses, pathogens and nearly all microorganisms. Sterilization is
any process that removes and eliminates all forms of microbial life, including
fungi, bacteria, viruses and others. Boiling water also can kill the vegetative
stage of all common microbes.
According to the Wilderness Medical Society, water temperatures above 160°F (70°C)
kill all pathogens within 30 minutes and above 185°F (85°C) within a few
minutes. So in the time it takes for the water to reach the boiling point
(212°F or 100°C) from 160°F (70°C), all pathogens will be killed, even at high
altitude. For safety, let the water boil rapidly for one minute, especially at
higher altitudes since water boils at a lower temperature.
Boiling water is the
preferred method of purification because disease-causing- microorganisms cannot
survive the intense heat. Pour the water back and forth from one clean
container to another to improve the taste. Then, add a pinch of salt because it
also may helps in killing microorganisms.
2.3.1.2 Steam Turbine
A steam turbine is a device that extracts thermal
energy from pressurized steam and uses it to do mechanical
work on a rotating output
shaft. The turbine generates rotary
motion, it is particularly suited to be used to drive an electrical generator.
A rotor of modern steam turbine, used in a power plant.
The
steam turbine is a form of heat engine that derives much of its improvement
in thermodynamic efficiency through the use of multiple stages in
the expansion of the steam, which results in a closer approach to the ideal reversible process. In the
United States (1996), about 90% of all electricity generation is by use of
steam turbines.
The steam turbine continues to be a major factor in
generating electric power throughout the world. As mentioned earlier, there are
basically three stages of matter which is solid, liquid and gas. Each stage is
held together by a different level of molecular force. With the ability of
water, gaseous steam takes up space due to its molecules being furthest apart.
However, when enough pressure is applied to steam,
an amazing process happens. The molecules are forced together to the point that
the water becomes more like a liquid again, while retaining the properties of
gases. In this point, it will become a supercritical fluid.
In steam turbine, water is actually heated to such
a high pressure that boiling does not even occur. As a result, the
supercritical steam provides excellent energy efficiency. With the help of high
pressure, the steam turbine can operates too much higher speeds.
3.0 CONCLUSION
Data loggers help in better
understanding of scientific experimentation. Other than that, the used of data
logger for determine the state of matter can get specific and accurate data
reading that might not be accurate due to parallax error when it is done
manually.
REFERENCE:
Retrieved from http://www.bbc.co.uk/schools/gcsebitesize/ict/measurecontrol/3dataloggingrev2.shtml on 6 November 2012 ( image)
Retrieved from http://forums.penny-arcade.com/discussion/28323/sterilization-temperature-of-water on 7 November 2012
Retrieved from http://www.ohsep.louisiana.gov/factsheets/locatingsafedrinkingwate.htm
on 7 November 2012
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