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| Reverse Osmosis |
Reverse osmosisThe term reverse osmosis comes from the process of osmosis, the natural movement of solvent from an area of low solute concentration, through a membrane, to an area of high solute concentration if no external pressure is applied.
In simple terms, reverse osmosis is the process of pushing a solution through a filter that traps the solute on one side and allows the pure solvent to be obtained from the other side. More formally, it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure. The membrane here is semipermeable, meaning it allows the passage of solvent but not of solute.
The membranes used for reverse osmosis have no pores, the separation takes place in a dense polymer layer of only microscopic thickness. In most cases the membrane is designed to only allow water to pass through. The water goes into solution in the polymer of which the membrane is manufactured, and crosses it by diffusion. This process requires that a high pressure be exerted on the high concentration side of the membrane, usually 5 MPa - 20 MPa (50 bar - 200 bar).
This process is best known for its use in desalination - removing the salt from sea water to get fresh water and has been used in this way since the early 1970s.
Method
When two solutions with different concentrations of a solute are mixed together, the total amount of solutes in the two solutions will be equally distributed in the total amount of solvent from the two solutions. This is achieved by diffusion, in which solutes will move from areas of higher concentration to areas of lower concentrations until the concentration in all the different areas of the resulting mixture are the same, a state called equilibrium.
Instead of mixing the two solutions together, they can be put in two compartments where they are separated from each other by a semipermeable membrane. The semipermeable membrane does not allow the solutes to move from one compartment to the other, but allows the solvent to move. Since equilibrium cannot be achieved by the movement of solutes from the compartment with high solute concentration to the one with low solute concentration, it is instead, achieved by the movement of the solvent from areas of low solute concentration to areas of high solute concentration. When the solvent moves away from low concentration areas, it causes these areas to become more concentrated. On the other side, when the solvent moves into areas of high concentration, solute concentration will decrease. This process is termed osmosis. The tendency for solvent to flow through the membrane can be expressed as "osmotic pressure", since it is analogous to flow caused by a pressure differential.
In reverse osmosis, in a similar setup as that in osmosis, pressure is applied to the compartment with high concentration. In this case, there are two forces to consider influencing the movement of water: the pressure caused by the difference in solute concentration between the two compartments (the osmotic pressure) and the externally applied pressure. In the same way as in conventional osmosis, the solute cannot move from areas of high pressure to areas of low pressure because the membrane is not permeable to it, only the solvent can pass through the membrane. When the effect of the externally applied pressure is greater than that of the concentration difference, net solvent movement will be from areas of high solute concentration to low solute concentration, and reverse osmosis occurs.
Reverse osmosis in use
Drinking water purification
In July 2002, Singapore announced that a process named NEWater would be a significant part of its future water plans. It involves using reverse osmosis to treat domestic wastewater before discharging the NEWater back into the reservoirs. [http://www.irc.nl/source/item.php/130]
In the United States, household drinking water filtration systems, including a reverse osmosis step, are commonly used for improving water for drinking and cooking.
Such systems typically include four or five stages:
- a sediment filter to trap particles including rust and calcium carbonate
- optionally a second sediment filter with smaller pores
- a carbon filter to trap organic chemicals and chlorination
- a reverse osmosis filter with a thin film composite membrane (TFM or TFC)
- optionally a second carbon filter
In some systems, the carbon pre-filter is omitted and cellulose triacetate membrane (CTA) is used. The CTA membrane is prone to rotting unless protected by the chlorinated water, while the TFC membrane is prone to breaking down under the influence of chlorine. In CTA systems, a carbon post-filter is needed to eliminate the chlorine.
Application of reverse osmosis in food industry
Other than desalination, reverse osmosis is a more economical unit opearation for concentrating food liquids e.g. fruit juices, than conventional heat-treatment processes. Research has been done on concentration of orange juice and tomato juice. It's advantages include a low operating cost and the ability to avoid heat treatment processes, which makes it suitable for heat-sensetive substances like the protein and enzymes found in most food products.
Maple syrup production
Starting in the 1970s, some maple syrup producers started using reverse osmosis to remove water from sap before being further boiled down to syrup. The use of reverse osmosis allows approximately 75 to 80 percent of the water to be removed from the sap, reducing energy consumption and exposure of the syrup to high temperatures. Microbial contamination and degradation of the membranes has to be monitored.
See also
- Osmosis
- Desalination
- RO Desalination
External links
- [http://www.ntu.edu.sg/cwp/mst/ Membrane Separation and Treatment]
- [http://ohioline.osu.edu/b856/b856_84.html Chapter 7: North American Maple Syrup Producers Manual] - discusses the use of reverse osmosis in maple syrup production.
Category:Water
Category:Filters
ja:逆浸透膜
Osmosis:For the film, see Osmosis Jones, which is also the alias of a famed botanist.
Osmosis is the diffusion of a solvent through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration. The semipermeable membrane is permeable to the solvent, but not to the solute, resulting in a chemical potential difference across the membrane which drives the diffusion. That is, the solvent flows from the side of the membrane where the solution is weakest to the side where it is strongest, until the solution on both sides of the membrane is the same strength (that is, until the chemical potential is equal on both sides).
chemical potential
Osmosis is an important topic in biology because it provides the primary means by which water is transported into and out of cells.
Explanation
Consider and focus on a semi-permeable membrane that allows water to pass through it, but not larger solutes such as salt. First, suppose such a membrane separates two volumes of pure water. At a macro scale, there will be no flow from one side of the membrane to the other, but at a micro scale, every time a water molecule hits the membrane, it has a certain probability of passing through; individual molecules are passing through the membrane all the time, but the circumstances on both sides are the same so the net flow is zero. Now imagine the same membrane separates a volume of pure water from a volume of a solution. A water molecule hits the membrane, it has a certain chance of passing through, but because there are fewer water molecules per volume in the solution, the water molecules on that side will collide with the wall less frequently. As a result, there will be a net flow of fresh water to the side with the solution. Assuming the membrane does not break, this net flow will slow and finally stop as the pressure on the solution side becomes such that the diffusion in each direction is equal.
Example of osmosis
A practical example of this can be seen in red blood cells. These contain a high concentration of solutes including salts and protein. When the cells are placed in a hypotonic solution, water rushes in to the area of high solute concentration, bursting the cell. This bursting of the cell is refered to as cytolysis.
Many plant cells use osmosis. This is because the osmotic entry of water is opposed and eventually equalled by the pressure exerted by the cell wall, creating a steady state. In fact, osmotic pressure is the main cause of support in plant leaves.
When a plant cell is placed in a hypertonic solution, the water in the cells moves to an area higher in solute concentration, and the cell shrinks and so becomes frigid. (In regard to the red blood cells mentioned earlier, this phenomenon is known as crenation.) This means the cell has become plasmolysed - the cell membrane has completely left the cell wall due to lack of water pressure on it.
In unusual environments, osmosis can be very harmful to organisms. For example, freshwater and saltwater aquarium fish placed in water with a different salt level (than they are adapted to) will die quickly, and in the case of saltwater fish rather dramatically. In addition, note the use of table salt to kill leeches and slugs.
Chemical potential
When a solute is dissolved in a solvent, the random mixing of the two species results in an increase in the entropy of the system, which corresponds to a reduction in the chemical potential. For the case of an ideal solution the reduction in chemical potential corresponds to:
:
where is the gas constant, is the temperature and is the solute concentration in terms of mole fraction. Most real solutions approximate ideal behavior for low solute concentrations (At higher concentrations interactions between solute and solvent cause deviations from Equation 1). This reduced potential creates a driving force and it is this force which drives diffusion of water through the semipermeable membrane.
Osmotic pressure
As mentioned before, osmosis can be opposed by increasing the pressure in the region of high solute concentration with respect to that in the low solute concentration region. The force per unit area required to prevent the passage of water through a selectively-permeable membrane and into a solution of greater concentration is equivalent to the osmotic pressure of the solution, or turgor. Osmotic pressure is a colligative property, meaning that the property depends on the concentration of the solute but not on its identity.
Increasing the pressure increases the chemical potential of the system in proportion to the molar volume (). Therefore, osmosis stops, when the increase in potential due to pressure equals the potential decrease from Equation 1, i.e.:
:
Where is the osmotic pressure and is the molar volume of the solvent.
For the case of very low solute concentrations, -ln(1-) ≈ and Equation 2 can be rearranged into the following expression for osmotic pressure:
:
Reverse osmosis
The osmosis process can be driven in reverse with solvent moving from a region of high solute concentration to a region of low solute concentration by applying a pressure in excess of the osmotic pressure. This reverse osmosis technique is commonly applied to purify water. Sometimes the term "forward osmosis" is used for osmosis, particularly when used for rehydrating dried food using contaminated water.
See also
- Diffusion
- Active transport
- Reverse osmosis
- Osmotic pressure
- Plasmolysis
Category:Diffusion
Solution
:This article is about a chemical solution; for other uses of the term "solution", see solution (disambiguation)
solution (disambiguation)]]
In chemistry, a solution is a homogeneous mixture of one or more substances (the solutes) dissolved in another substance (the solvent). A common example would be a solid dissolving into a liquid, like salt or sugar dissolving in water (or even gold into mercury, forming an amalgam); but also gases may dissolve into liquids, like carbon dioxide or oxygen in water, and liquids and gases into themselves.
An ideal solution is one where the interactions of the molecules of the solvent with each other are equal to their interactions with the solutes. The properties of an ideal solution can be calculated by the linear combination of the properties of its components.
The solvent is conventionally defined as the substance that exists in a greater quantity than the solute(s) in the solution. If both solute and solvent exist in equal quantities (such as in a 50% ethanol 50% water solution), the concepts of "solute" and "solvent" become less relevant, but the substance that is more often used as a solvent is normally designated as the solvent (in this case, water).
Solvents can be broadly classified into polar and non-polar solvents A common measure of the polarity of a solvent is the dielectric constant. The most widely used polar solvent is water, with a dielectric constant of 78.5. Ethanol, with a dielectic constant of 24.3, has intermediate polarity. An example of a non-polar solvent is hexane, which has a dielectic constant of 1.9. Generally polar or ionic compounds will only dissolve in polar solvents. A simple test for the polarity of a liquid solvent is to rub a plastic rod, to induce static electricity. Then hold this charged rod close to a running stream of the solvent. If the path of the solvent deviates when the rod is held close to it, it is a polar solvent. Certain molecules have polar and non-polar regions, for example Sodium dodecyl sulfate. This class of molecules (called amphipathic molecules) includes surfactants like soaps and emulsifiers, as they have the ability to stabilize emulsions by aligning themselves on the interface between the non-polar and polar liquids, with their polar ends in the polar liquid and their non-polar ends in the non-polar liquid.
When a solute is dissolved into a solvent, especially polar solvents, a structure forms around it (a process called solvation), which allows the solute-solvent interaction to remain stable.
When no more of a solute can be dissolved into a solvent, the solution is said to be saturated. However the point at which a solution can become saturated changes significantly with different environmental factors, such as temperature, pressure, and contamination. Raising the solubility (such as by increasing the temperature) to dissolve more solute, and then lowering the solubility causes a solution to become supersaturated.
In general the greater the temperature of a solvent, the more of a given solute it can dissolve. However, some compounds exhibit reverse solubility, which means that as a solvent gets warmer, less solute can be dissolved. Some surfactants exhibit this behaviour.
There are several ways to measure the strength of a solution; see concentration for more information.
There are many types of solutions:
References
See also
- Colligative properties
- Colloid
- Making up solutions
- Molar solution
- Percentage solution
- Solubility equilibrium
- Soluble
- Suspension (chemistry)
Category:Homogeneous mixtures
Category:Alchemical processes
ko:용액
ja:溶液
Solute
:This article is about a chemical solution; for other uses of the term "solution", see solution (disambiguation)
solution (disambiguation)]]
In chemistry, a solution is a homogeneous mixture of one or more substances (the solutes) dissolved in another substance (the solvent). A common example would be a solid dissolving into a liquid, like salt or sugar dissolving in water (or even gold into mercury, forming an amalgam); but also gases may dissolve into liquids, like carbon dioxide or oxygen in water, and liquids and gases into themselves.
An ideal solution is one where the interactions of the molecules of the solvent with each other are equal to their interactions with the solutes. The properties of an ideal solution can be calculated by the linear combination of the properties of its components.
The solvent is conventionally defined as the substance that exists in a greater quantity than the solute(s) in the solution. If both solute and solvent exist in equal quantities (such as in a 50% ethanol 50% water solution), the concepts of "solute" and "solvent" become less relevant, but the substance that is more often used as a solvent is normally designated as the solvent (in this case, water).
Solvents can be broadly classified into polar and non-polar solvents A common measure of the polarity of a solvent is the dielectric constant. The most widely used polar solvent is water, with a dielectric constant of 78.5. Ethanol, with a dielectic constant of 24.3, has intermediate polarity. An example of a non-polar solvent is hexane, which has a dielectic constant of 1.9. Generally polar or ionic compounds will only dissolve in polar solvents. A simple test for the polarity of a liquid solvent is to rub a plastic rod, to induce static electricity. Then hold this charged rod close to a running stream of the solvent. If the path of the solvent deviates when the rod is held close to it, it is a polar solvent. Certain molecules have polar and non-polar regions, for example Sodium dodecyl sulfate. This class of molecules (called amphipathic molecules) includes surfactants like soaps and emulsifiers, as they have the ability to stabilize emulsions by aligning themselves on the interface between the non-polar and polar liquids, with their polar ends in the polar liquid and their non-polar ends in the non-polar liquid.
When a solute is dissolved into a solvent, especially polar solvents, a structure forms around it (a process called solvation), which allows the solute-solvent interaction to remain stable.
When no more of a solute can be dissolved into a solvent, the solution is said to be saturated. However the point at which a solution can become saturated changes significantly with different environmental factors, such as temperature, pressure, and contamination. Raising the solubility (such as by increasing the temperature) to dissolve more solute, and then lowering the solubility causes a solution to become supersaturated.
In general the greater the temperature of a solvent, the more of a given solute it can dissolve. However, some compounds exhibit reverse solubility, which means that as a solvent gets warmer, less solute can be dissolved. Some surfactants exhibit this behaviour.
There are several ways to measure the strength of a solution; see concentration for more information.
There are many types of solutions:
References
See also
- Colligative properties
- Colloid
- Making up solutions
- Molar solution
- Percentage solution
- Solubility equilibrium
- Soluble
- Suspension (chemistry)
Category:Homogeneous mixtures
Category:Alchemical processes
ko:용액
ja:溶液
Solvent
A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. The most common solvent in everyday life is water. The term organic solvent refers to most other solvents that are organic compounds and contain carbon atoms. Solvents usually have a low boiling point and evaporate easily or can be removed by distillation, thereby leaving the dissolved substance behind. Solvents should therefore not react chemically with the dissolved compounds — they have to be inert. Solvents can also be used to extract soluble compounds from a mixture, the most common example is the brewing of coffee or tea with hot water. Solvents are usually clear and colorless liquids and most of them have a characteristic smell. The concentration of a solution is the amount of compound that is dissolved in a certain volume of solvent. The solubility is the maximal amount of compound that is soluble in a certain volume of solvent at a specified temperature.
Common uses for organic solvents are in dry cleaning (e.g. tetrachloroethylene), as paint thinners (e.g. toluene, turpentine), as nail polish removers and glue solvents (acetone, methyl acetate, ethyl acetate), in spot removers (e.g. hexane, petrol ether), in detergents (citrus terpenes), in perfumes (ethanol), and in chemical syntheses.
Polarity, solubility, and miscibility
Solvents and solutes can be broadly classified into polar (hydrophilic) and non-polar (lipophilic). The polarity can be measured as the dielectric constant or the dipole moment of a compound. The polarity of a solvent determines what type of compounds it is able to dissolve and with what other solvents or liquid compounds it is miscible with. As a rule of thumb, polar solvents dissolve polar compounds best and non-polar solvents dissolve non-polar compounds best: "like dissolves like". Strongly polar compounds like inorganic salts (e.g. table salt) or sugars (e.g. sucrose) dissolve only in very polar solvents like water, while strongly non-polar compounds like oils or waxes dissolve only in very non-polar organic solvents like hexane. Similarly, water and hexane (or vinegar and salad oil) are not miscible with each other and will quickly separate into two layers even after being shaken well.
Protic and aprotic solvents
Polar solvents can be further subdivided into polar protic solvents and polar aprotic solvents. Water (H-O-H), ethanol (CH3-CH2-OH), or acetic acid (CH3-C(=O)OH) are representative polar protic solvents. A polar aprotic solvent is acetone (CH3-C(=O)-CH3). In chemical reactions the use of polar protic solvents favors the SN1 reaction mechanism, while polar aprotic solvents favor the SN2 reaction mechanism.
Boiling point
Another important property of solvents is their boiling point that also determines the speed of evaporation. Small amounts of low-boiling solvents like diethyl ether, methylene chloride, or acetone will evaporate in seconds at room temperature, while high-boiling solvents like water or dimethylsulfoxide need higher temperatures, an air flow, or the application of vacuum for fast evaporation.
Density
Most organic solvents have a lower density than water. Therefore they are lighter and will separate on top of water. An important exception are many halogenated solvents like methylene chloride or chloroform that will sink to the bottom. This is important to remember when partitioning compounds between solvents and water in a separatory funnel during chemical syntheses.
Chemical interactions
A solvent will create various weak chemical interactions with the solute in order to solubilize it. The most common of these interactions are the relatively weak van der Waals interactions (induced dipole interactions), the stronger dipole-dipole interactions, and the even stronger hydrogen bonds (interaction between O-H or N-H hydrogens with O or N atoms).
Safety
Most organic solvents are flammable or highly flammable, depending on their volatility. Exceptions are some chlorinated solvents like methylene chloride and chloroform. Mixtures of solvent vapors and air can explode. Solvent vapors are heavier than air, they will sink to the bottom and can travel large distances nearly undiluted. Solvent vapors can also form in supposedly empty drums and cans, posing a flash fire hazard; hence empty containers of volatile solvents should be stored open and upside down.
Ethers like diethyl ether and tetrahydrofuran (THF) can form highly explosive organic peroxides upon exposure to oxygen and light. These peroxides will concentrate during distillation due to their higher boiling point. Ethers have to be stored in the dark in closed canisters in the presence of stabilizers like BHT or over sodium hydroxide.
Many solvents can lead to a sudden loss of consciousness if inhaled in larger amounts. Solvents like diethyl ether and chloroform have been used in medicine as anesthetics and narcotics for a long time. Ethanol is a widely used and abused psychoactive drug. Diethyl ether, chloroform, and many other solvents (e.g. from gasoline or glues) are used recreationally in glue sniffing, often with harmful long term health effects like neurotoxicity or cancer.
Some solvents including chloroform and benzene (an ingredient of gasoline) are carcinogenic. Many others can damage internal organs like the liver, the kidneys, or the brain. Methanol can cause internal damage to the eyes including permanent blindness.
General precautions
- Avoid the generation of solvent vapors by working in a fume hood or a well ventilated area
- Keep the storage containers tightly closed.
- Never use open flames near flammable solvents, use electrical heating instead.
- Never flush flammable solvents down the drain to avoid explosions and fires.
- Avoid the inhalation of solvent vapors.
- Avoid contact of the solvent with the skin — many solvents are easily absorbed through the skin.
Properties table of common solvents
The solvents are grouped into non-polar, polar aprotic, and polar protic solvents and ordered by increasing polarity. The polarity is given as the dielectric constant. The density of unpolar solvents that are heavier than water is bolded.
See also
- LogP or partition coefficient is a measure of differential solubility of a compound in two solvents
- Solvent systems exist outside the realm of ordinary organic solvents: Supercritical fluids, ionic liquids and deep eutectic solvents.
External links
- [http://www.speckanalytical.co.uk/products/Tips/bps.html Table] Properties of common organic solvents
- [http://www.usm.maine.edu/~newton/Chy251_253/Lectures/Solvents/Solvents.html Table and text] O-Chem Lecture
- [http://virtual.yosemite.cc.ca.us/smurov/orgsoltab.htm Tables] Properties and toxicities of organic solvents
Category:Solutions
Category:Chemical compounds
ko:용매
ja:溶媒
Semipermeable
A semipermeable membrane (or more accurately a selectively permeable membrane, or differentially permeable membrane) is a membrane which will allow certain molecules or ions to pass through it by diffusion (sometimes "facilitated diffusion"). The rate of passage depends on the pressure, concentration and temperature of the molecules (or "solutes") on either side, as well as the permeability of the membrane to each solute.
Depending on the membrane and the solute, permeability may depend on solute size, solubility properties, or chemistry. An example of a semi-permeable membrane is a lipid bilayer, on which is based the plasma membrane that surrounds all biological cells. Many natural and synthetic materials thicker than a membrane are also semipermeable. An example of this is the thin film on the inside of an egg.
See also
- Osmosis
- Reverse osmosis
Category:Cell biology
Category:Chemistry
ja:半透膜
Pascal
----
The pascal (symbol: Pa) is the SI unit of pressure. It is equivalent to one newton per square metre. The same unit is also used for stress, Young's modulus, and tensile strength.
Definition
1 pascal (Pa) = 1 N/m2 = 1 J/m3 = 1 kg·m–1·s–2
SI multiples
Origin
The unit is named after Blaise Pascal, the eminent French mathematician, physicist, and philosopher.
Explanation
1 megapascal (MPa) = 1 000 000 Pa = 1 N/mm2.
Standard atmospheric pressure is 101 325 Pa = 101.325 kPa = 1013.25 hPa = 1013.25 mbar = 760 Torr (ISO 2533).
Meteorologists worldwide have for a long time measured atmospheric pressure in millibars. After the introduction of SI units, many preferred to preserve the customary pressure figures. Therefore, meteorologists use hectopascals today for air pressure, which are equivalent to millibars, while similar pressures are given in kilopascals in practically all other fields, where the hecto prefix is hardly ever used.
: 1 hectopascal (hPa) = 100 Pa = 1 mbar.
: 1 kilopascal (kPa) = 1000 Pa = 10 hPa.
In the former Soviet mts system, the unit of pressure is the pieze, which is equivalent to one kilopascal.
The Unicode computer character set has dedicated symbols ㎩ for Pa and ㎪ for kPa, but these exist merely for backward-compatibility with some older ideographic character-sets.
Comparison to other units of pressure
See also
- Orders of magnitude (pressure)
Category:SI derived units
Category:Units of pressure
ko:파스칼
ja:パスカル
Bar (unit)A bar (symbol bar) is a unit of pressure. It is not an SI unit. It is accepted (although discouraged) for use with the SI. The bar is still widely used in descriptions of pressure because it is about the same as atmospheric pressure.
Definition
The bar is defined as:
- 1 bar = 100 000 pascals (Pa) = 100 kPa = 1 000 000 dynes/square centimetre
Conversions
- 1 bar = 100 kN/m²
Origin
The word bar finds its origin in the Greek word báros, meaning weight. Its official symbol is "bar"; the earlier "b" is now deprecated, but still often seen especially as "mb" rather than the proper "mbar" for millibars.
Discussion
Atmospheric air pressure is often given in millibars where "standard" sea level pressure is defined as 1013.25 mbar (hPa), equal to (1.01325 bar). The millibar is also not an SI unit of measure; however, it is still used locally in meteorology when describing atmospheric pressure. The SI unit is the pascal (Pa), with 1 mbar = 100 Pa = 1 hPa = 0.1 kPa. Meteorologists worldwide have long measured air pressure in millibars. After the introduction of SI units, many preferred to preserve the customary pressure figures. Therefore, some continue to use millibars under their own name, while others use hPa (which are equivalent to millibars) so they could stick to the same numeric scale. Similar pressures are given in kilopascals in practically all other fields where the hecto prefix is hardly ever used. In Canadian weather reports, the normal is kPa.
In everyday use, pressure is often measured with reference to atmospheric pressure. This is gauge pressure and denoted by barg, often written with no spaces, spoken "bar gauge", and sometimes using symbols such as 'bar(g)'. For example, if someone says that their car tires are pressured up to 2.3 bar they actually mean bars gauge: the pressure in the tire is really 3.3 bar, but only 2.3 bar above atmospheric, which is the scale a tire gauge would read. When absolute pressure is desired, it is sometimes denoted 'bara' or 'bar(a)' for "bar absolute". The alteration of the symbols of units of measure for this purpose is now deprecated.
External links
- [http://www.bipm.org/en/si/si_brochure/chapter4/4-1.html Official SI website: Table 8. Other non-SI units currently accepted for use with the International System Their use is not encouraged.]
ja:バール (単位)
Sea waterSea water is water from a sea or ocean. On average, sea water in the world's oceans has a salinity of ~3.5%. This means that for every 1 litre (1000mL) of sea water there are 35 grams of salts (mostly, but not entirely, sodium chloride) dissolved in it. This can be expressed as 0.6M NaCl. Water with this level of osmolality is, of course, not potable.
Sea water is not uniformly saline throughout the world. The planet's freshest sea water is in the Gulf of Finland, part of the Baltic Sea. The most saline open sea is the Red Sea, where high temperatures and confined circulation result in high rates of surface evaporation and there is little fresh inflow from rivers. The salinity in isolated seas (for example, the Dead Sea) can be considerably greater.
The density of sea water is between 1020 and 1030 kg/m3. Due to chemical buffering, seawater pH is limited to the range 7.5 to 8.4.
Ocean salinity
Scientific theories behind the origins of sea salt started with Sir Edmond Halley in 1715, who proposed that salt and other minerals were carried into the sea by rivers, having been leached out of the ground by rainfall runoff. Upon reaching the ocean, these salts would be retained and concentrated as the process of evaporation (see Hydrologic cycle) removed the water. Halley noted that of the small number of lakes in the world without ocean outlets (such as the Dead Sea and the Caspian Sea), most have high salt content. Halley termed this process "continental weathering".
Halley's theory is partly correct. In addition, sodium was leached out of the ocean floor when the oceans first formed. The presence of the other dominant element of salt, chloride, results from "outgassing" of chloride (as hydrochloric acid) with other gases from Earth's interior via volcanos and hydrothermal vents. The sodium and chloride subsequently became the most abundant constituents of sea salt.
Ocean salinity has been stable for millions of years, most likely as a consequence of a chemical/tectonic system which recycles the salt. Since the ocean's creation, sodium is no longer leached out of the ocean floor, but instead is captured in sedimentary layers covering the bed of the ocean. One theory is that plate tectonics result in salt being forced under the continental land masses, where it is again slowly leached to the surface.
Cultural aspects
Even on a ship or island in the middle of the ocean, there can be a "shortage of water" meaning, of course, a shortage of fresh water. This is described most famously by a line from Samuel Taylor Coleridge's The Rime of the Ancient Mariner:
:"Water, water, every where
:Nor any drop to drink."
Seawater can be turned into drinkable (potable) water by one of a number of desalination processes. Otherwise, it should not be drunk because of its high dissolved mineral content. Effectively because more water must be expended to eliminate these minerals (through excretion in urine) than is gained from drinking the seawater itself.
Sea water for flushing toilet
Hong Kong has an extensive use of sea water for flushing toilets citywide. More than 90% of its toilets are flushed by sea water as a means of conserving fresh water resources. The development of this approach was started in the 1960s and 1970s when water shortages became a severe problem as the population of the (then) British colony grew. The most interesting aspect of this approach is how the sewage is treated. Saline water cannot be treated (in a waste water treatment plant) by the usual methods.
See also
- Fresh water
External links
- http://www.sealevelcontrol.com/
- http://ic.ucsc.edu/~acr/ocea1/chemoc_files/Seawater.htm
Category:Chemical oceanography
Category:Liquid water
Category:Physical oceanography
ja:海水
Diffusion:This article is about the physical mechanism of diffusion. For alternative meanings, see diffusion (disambiguation).
Diffusion, being the spontaneous spreading of matter (particles), heat, or momentum, is one type of transport phenomena. It is readily observed for example when dried foodstuff like spaghetti is cooked; water molecules diffuse into the spaghetti strings, making them thicker and more flexible. It is a physical process rather than a chemical reaction, which requires no net energy expenditure. In cell biology, diffusion is often described as a form of passive transport, by which substances cross membranes.
Examples of diffusion
- A balloon filled with helium will deflate a little bit every day, because helium atoms diffuse out of the balloon through its wall
- When spaghetti is cooked, water molecules diffuse into the spaghetti strings, making them thicker and more flexible. Adding salt to the water reduces diffusion by reducing the osmotic pressure.
- Carbon dioxide bubbles in soft drinks start as small nuclei and grow because of the diffusion of carbon dioxide molecules towards them
- Heat diffuses through the walls of a mug filled with hot coffee
- A gas distributes itself over a room by diffusion
- A sugar cube in a glass of water that is not stirred will dissolve slowly and the sugar molecules will distribute over the water by diffusion
The nature of diffusion
The different forms of diffusion can be modelled quantitatively using the diffusion equation, which goes by different names depending on the physical situation. For instance - steady-state bi-molecular diffusion is governed by Fick's first law, steady-state thermal diffusion is governed by Fourier's law. The diffusion of electrons in an electrical field leads essentially to Ohm's law (see Einstein relation). The generic diffusion equation is time dependent, i.e., applies to non-steady-state situations as well.
In all cases of diffusion, the net flux of the transported quantity (atoms, energy, or electrons) is equal to a physical property (diffusivity, thermal conductivity, electrical conductivity) multiplied by a gradient (a concentration, thermal, electric field gradient). Noticeable transport occurs only if there is a gradient - for example in thermal diffusion, if the temperature is constant, heat will move as quickly in one direction as in the other, producing no heat transport and change in temperature.
Diffusion occurs as a result of the Second Law of Thermodynamics, which states that the entropy or disorder of any system must always increase with time. Because substances diffuse from regions of higher concentration to regions of lower concentration, they are going from a state of higher order to a state of lower order, in accordance with the Second Law of Thermodynamics. Therefore, diffusion is a spontaneous, natural process, and to reverse diffusion would require the expenditure of energy to counteract the higher order of the system and prevent a violation of the laws of entropy.
Types of diffusion
Diffusion does not only refer to diffusion of particles, it refers to all transport phenomena occurring within thermodynamic systems under the influence of thermal fluctuations (i.e under the influence of disorder; this excludes transport through an hydrodynamic flow, which is a macroscopic, ordered phenomena).
Diffusion is the process through which an inhomogeneous thermodynamic system at local thermodynamic equilibrium returns to global thermodynamic equilibrium, through the homogeneisation of the values of its intensive parameters.
- Atomic diffusion
- Brownian motion, for example of a single particle in a solvant
- Collective diffusion, the diffusion of a large number of (possibly interacting) particles
- Electron diffusion, resulting in electric current
- Heat flow (thermal diffusion)
- Momentum diffusion, ex. the diffusion of the hydrodynamic velocity field
- Osmosis
- Photon diffusion
- Reverse diffusion
Diffusion across biological membranes
- Facilitated diffusion
- Ion diffusion through ion channels
- Simple diffusion, not requiring a special protein channel
- Diffusion in the respiratory system - in the alveoli of mammalian lungs, due to differences in partial pressures across the alveolar-capillary membrane, oxygen diffuses into the blood and carbon dioxide diffuses out
See also
- Bohm diffusion
- Brownian motion
- Collective diffusion
- Diffusion equation
- Diffusion MRI
- Fick's law of diffusion
- Isotope separation
- Mass transfer
- Osmosis
- Transport phenomena
External links
- [http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html Some pictures that display diffusion and osmosis]
ja:拡散
Equilibrium:For the science fiction film, see Equilibrium (2002 film)
----
Equilibrium or balance is any of a number of related phenomena in the natural and social sciences. In general, a system is said to be in a state of equilibrium if all influences on the system are cancelled by the effects of others. A related concept is stability; an equilibrium may or may not be stable.
- Some examples from the physical sciences:
- Thermodynamic equilibrium, the state of a system in which its internal processes cause no net change in its macroscopic properties (such as temperature and pressure).
- Chemical equilibrium, the state in which a chemical reaction proceeds at the same rate as its reverse reaction, resulting in no net change in the amount of each compound.
- A system is in mechanical equilibrium when the sum of the forces and moments on each particle of the system is zero.
- Quasistatic equilibrium, the state of a system in which internal processes evolve or change gradually from one equilibrium state to the next.
- The weighing instrument balance relies on an equilibrium.
- In electronics, a balanced signal is also called a differential signal.
- Some examples from the biological and social sciences:
- Physical balance of humans and animals is maintained with the aid of the sense of balance, and in special cases with a balance beam.
- Psychologically some balance between desires and satisfaction is important; somewhat paradoxically complete satisfaction may not be ideal, it can be argued that perhaps it is better if things are left to be desired.
- An addiction is any of various forms of unbalanced behavior.
- In economics, static equilibrium and general equilibrium
- Nash equilibrium in game theory, an optimum strategy for all players in a game, in the sense that no one player can benefit by changing his strategy while all other players keep theirs the same.
- Reflective equilibrium in ethics, a state in which the consequences of one's general principles are consistent with one's opinions about individual cases.
- For individuals and organisations a balance between income and expenses is often important, especially in the long run.
- In various practical matters an equilibrium is useful, e.g. in a conversation, between talking and listening, or in a personal relationship, between giving and taking.
- Equilibrium is also a german viking metal band
Semipermeable membrane
A semipermeable membrane (or more accurately a selectively permeable membrane, or differentially permeable membrane) is a membrane which will allow certain molecules or ions to pass through it by diffusion (sometimes "facilitated diffusion"). The rate of passage depends on the pressure, concentration and temperature of the molecules (or "solutes") on either side, as well as the permeability of the membrane to each solute.
Depending on the membrane and the solute, permeability may depend on solute size, solubility properties, or chemistry. An example of a semi-permeable membrane is a lipid bilayer, on which is based the plasma membrane that surrounds all biological cells. Many natural and synthetic materials thicker than a membrane are also semipermeable. An example of this is the thin film on the inside of an egg.
See also
- Osmosis
- Reverse osmosis
Category:Cell biology
Category:Chemistry
ja:半透膜
Osmosis:For the film, see Osmosis Jones, which is also the alias of a famed botanist.
Osmosis is the diffusion of a solvent through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration. The semipermeable membrane is permeable to the solvent, but not to the solute, resulting in a chemical potential difference across the membrane which drives the diffusion. That is, the solvent flows from the side of the membrane where the solution is weakest to the side where it is strongest, until the solution on both sides of the membrane is the same strength (that is, until the chemical potential is equal on both sides).
chemical potential
Osmosis is an important topic in biology because it provides the primary means by which water is transported into and out of cells.
Explanation
Consider and focus on a semi-permeable membrane that allows water to pass through it, but not larger solutes such as salt. First, suppose such a membrane separates two volumes of pure water. At a macro scale, there will be no flow from one side of the membrane to the other, but at a micro scale, every time a water molecule hits the membrane, it has a certain probability of passing through; individual molecules are passing through the membrane all the time, but the circumstances on both sides are the same so the net flow is zero. Now imagine the same membrane separates a volume of pure water from a volume of a solution. A water molecule hits the membrane, it has a certain chance of passing through, but because there are fewer water molecules per volume in the solution, the water molecules on that side will collide with the wall less frequently. As a result, there will be a net flow of fresh water to the side with the solution. Assuming the membrane does not break, this net flow will slow and finally stop as the pressure on the solution side becomes such that the diffusion in each direction is equal.
Example of osmosis
A practical example of this can be seen in red blood cells. These contain a high concentration of solutes including salts and protein. When the cells are placed in a hypotonic solution, water rushes in to the area of high solute concentration, bursting the cell. This bursting of the cell is refered to as cytolysis.
Many plant cells use osmosis. This is because the osmotic entry of water is opposed and eventually equalled by the pressure exerted by the cell wall, creating a steady state. In fact, osmotic pressure is the main cause of support in plant leaves.
When a plant cell is placed in a hypertonic solution, the water in the cells moves to an area higher in solute concentration, and the cell shrinks and so becomes frigid. (In regard to the red blood cells mentioned earlier, this phenomenon is known as crenation.) This means the cell has become plasmolysed - the cell membrane has completely left the cell wall due to lack of water pressure on it.
In unusual environments, osmosis can be very harmful to organisms. For example, freshwater and saltwater aquarium fish placed in water with a different salt level (than they are adapted to) will die quickly, and in the case of saltwater fish rather dramatically. In addition, note the use of table salt to kill leeches and slugs.
Chemical potential
When a solute is dissolved in a solvent, the random mixing of the two species results in an increase in the entropy of the system, which corresponds to a reduction in the chemical potential. For the case of an ideal solution the reduction in chemical potential corresponds to:
:
where is the gas constant, is the temperature and is the solute concentration in terms of mole fraction. Most real solutions approximate ideal behavior for low solute concentrations (At higher concentrations interactions between solute and solvent cause deviations from Equation 1). This reduced potential creates a driving force and it is this force which drives diffusion of water through the semipermeable membrane.
Osmotic pressure
As mentioned before, osmosis can be opposed by increasing the pressure in the region of high solute concentration with respect to that in the low solute concentration region. The force per unit area required to prevent the passage of water through a selectively-permeable membrane and into a solution of greater concentration is equivalent to the osmotic pressure of the solution, or turgor. Osmotic pressure is a colligative property, meaning that the property depends on the concentration of the solute but not on its identity.
Increasing the pressure increases the chemical potential of the system in proportion to the molar volume (). Therefore, osmosis stops, when the increase in potential due to pressure equals the potential decrease from Equation 1, i.e.:
:
Where is the osmotic pressure and is the molar volume of the solvent.
For the case of very low solute concentrations, -ln(1-) ≈ and Equation 2 can be rearranged into the following expression for osmotic pressure:
:
Reverse osmosis
The osmosis process can be driven in reverse with solvent moving from a region of high solute concentration to a region of low solute concentration by applying a pressure in excess of the osmotic pressure. This reverse osmosis technique is commonly applied to purify water. Sometimes the term "forward osmosis" is used for osmosis, particularly when used for rehydrating dried food using contaminated water.
See also
- Diffusion
- Active transport
- Reverse osmosis
- Osmotic pressure
- Plasmolysis
Category:Diffusion
Singapore
The Republic of Singapore (Simplified Chinese: 新加坡共和国; Pinyin: Xīnjiāpō Gònghéguó, Malay: Republik Singapura; Tamil: சிங்கப்பூர் குடியரசு), is an island city-state in Southeast Asia, situated on the southern tip of the Malay Peninsula, south of the Malaysian state of Johor and north of the Indonesian Riau Islands. Its coordinates are , just 137 km north of the Equator. The name Singapore was derived from Malay word singa (lion), which itself is derived from the Sanskrit word सिंह siMha of the same meaning, and the Sanskrit word पुर pura (city) .
Singapore developed from a small Malay fishing village to become a multicultural, major global city, while attracting controversy for some of its current government policies. Throughout history, it has been posssessed by multiple countries and empires and changed hands many times, including being in the possesion of Melaka and the Sultanate of Johore in ancient history, the British Empire in the colonial era, Japanese Empire in World War II and Malaysia after merger. It finally achieved independence in 1965. After independence, government-led rapid industrialisation and open policies inviting foreign investments stimulated rapid economic growth and the country is now regarded as a developed nation.
Presently, Singapore can be politically analysed as a democratic socialist country and has an extensive welfare system, although de facto it has a dominant-party system. The nation regards itself as multiracial, and the majority of the population are ethnic Chinese, with ethnic Indians, Malays and Eurasians being a significant minority. Singapore has little natural resources, so its economy must on exports of electronics and manufacturing from her port. More than 90% of Singapore's population lives in housing estates constructed by the Housing Development Board and nearly half utilises its public transport system daily. As a result of public transport and environmental initiatives by government ministries, Singapore's lack of pollution is a distinguishing characteristic from many other cities, and isolated to heavy industry located offshore in Jurong Island.
History
The first records of Singapore's existence are in Chinese texts from the 3rd century. The island was an outpost of the Sumatran Srivijaya empire and originally bore the Javanese name Temasek. Temasek rose to become a significant trading city, but subsequently declined. There are few remnants of old Temasek in Singapore other than archaeological evidence.
In the 15th and 16th century, Singapore was a part of the Sultanate of Johore. During the Malay-Portugal wars in 1617, Singapore was set ablaze by Portuguese troops.
1617, erected at the spot where he first landed at Singapore. He is recognised as the modern founder of Singapore.]] In 1819, Sir Thomas Stamford Raffles, a British East India Company official, made a treaty with the Sultan of Johore and established Singapore as a trading post and settlement, and saw instant growth and immigration from various ethnic groups. Singapore was later made a crown colony by Britain in 1867. After a series of territorial expansions, the British Empire soon raised it as an entrepot town due to its strategic location along the busy shipping routes connecting Europe to China.
During World War II, Japanese forces invaded Malaya and the surrounding region in the Battle of Malaya, culminating in the Battle of Singapore. The British were unprepared and swiftly defeated, despite having superior numbers of troops. They surrendered to the Japanese on February 15, 1942. The Japanese renamed Singapore as Syonan-to ("Light of the South") and occupied it until the Japanese defeat September 1945. In 1959, Singapore became a self-governing crown colony with Lee Kuan Yew from the People's Action Party (PAP) as the first Prime Minister of Singapore following the 1959 elections. After a national referendum in 1962, Singapore was admitted into the Federation of Malaysia along with Malaya, Sabah and Sarawak as a state with autonomous powers in September 1963. After heated ideological conflict developed between the state government formed by PAP and the Federal government in Kuala Lumpur, Singapore was expelled from the federation on August 7 1965. It gained official sovereignty two days later on August 9 1965 with Malaysia the first country to recognise it as an independent nation, the date becoming Singapore's National Day. Singapore's National Days are celebrated with annual parades and other festivities.
National Day]]
National Day]
The fledgling nation had to struggle for self-sufficiency, and faced problems including mass unemployment, housing shortages and the lack of land and natural resources, like oil. During Lee Kuan Yew's term as prime minister from 1959 to 1990, his administration curbed unemployment, raised the standard of living, developed Singapore's economic infrastructure and overcame problems such as lack of housing, social stability and an independent national defence. This elevated Singapore into developing nation and subsequently to developed status.
On 26 November 1990 Goh Chok Tong became prime minister. Under his tenure the country tackled the 1997 Asian financial crisis, the SARS outbreak in 2003 as well as terrorist threats posed by the Jemaah Islamiah (JI). Lee Hsien Loong, the eldest son of Lee Kuan Yew, became the third prime minister on 12 August 2004 after securing the confidence of a majority of Parliament, which is still dominated by the PAP.
Politics and government
:
Singapore is a republic with a Westminster system of a unicameral parliamentary government, with the bulk of the executive powers resting in the hands of a cabinet of ministers led by a prime minister. The office of the president was, historically, a ceremonial one as head of state, but the Constitution was amended in 1991 to create the position of a popularly elected president and also to grant the president veto powers in a few key decisions such as the use of the national reserves and the appointment of key judiciary positions. The legislative branch of government is the Parliament.
Politics of Singapore have been dominated by the People's Action Party (PAP) since its independence in 1965. Critics have called Singapore a de facto one party state and have accused the PAP of taking harsh actions against opposition parties to impede their success, including gerrymandering and the filing of civil suits against the opposition for libel or slander. The media arm of the Government applies a somewhat monopolistic grip on the local mainstream media, often subjecting it to stringent censorship, as a result, opposition political parties in Singapore hardly get any mention or coverage.
Critics claim that Singaporean courts have been favouring the government and the PAP in these lawsuits, although there were a few cases in which the opposition won. They consider the form of government in Singapore to be closer to authoritarianism rather than true democracy, and could be considered an illiberal democracy or procedural democracy.
Despite this, or perhaps because of it, Singapore has what many consider to be a highly successful and transparent market economy. PAP's policies contain certain aspects of socialism, which includes large scale public housing programme, public education system and the dominance of government controlled companies in the local economy. Although present in almost all segments of Singaporean society, the government has a clean, corruption-free image, and has consistently been rated as the least-corrupt country in Asia and amongst the top ten cleanest in the world by Transparency International since its first annual survey conducted in 1995.
Although Singapore's laws are inherited from British and British Indian laws, the PAP has also consistently rejected wholesale Western democratic values, with former prime minister Lee Kuan Yew citing incompatibilities with "Asian values". Singapore's position is that there should not be a "one-size-fits-all" solution to a democracy. Most recently, the PAP has relaxed some of its socially conservative policies and encouraged entrepreneurship.
Singapore enjoys one of the lowest crime rates in the world, as its laws are generally strict, and which has often been cited by foreign companies as one of the reasons for investing in Singapore. As the tiny city-state is a multi-racial society, materials that may breed ill-will among its population or cause religious disharmony are not tolerated, even on the Internet. In September 2005, three bloggers were charged with sedition for posting racist remarks targeting minorities, after admitting their guilt, the punishments handed down ranged from serving community service and fines to the maximum imprisonment of a month.
Some offences can lead to heavy fines or caning; laws provide for capital punishment in Singapore in cases of first-degree murder and drug trafficking. According to an Amnesty International report, 400 people were hanged between 1991 and 2004, which the report claimed is "possibly the highest execution rate in the world" per capita. However, the Singapore Government responded to AI's report in January 2004 on its Home Affairs website [http://www2.mha.gov.sg/mha/detailed.jsp?artid=990&type=4&root=0&parent=0&cat=0&mode=arc] and reiterated capital punishments as a sovereign right for the most serious crimes, a stance in common with democracies like Japan [http://www.japantimes.co.jp/cgi-bin/getarticle.pl5?nn20050917a2.htm] and the United States.
Geography
United States. ([http://maps.google.com/maps?ll=1.352692,103.804321&spn=0.473579,0.633396&t=k&hl=en details])]]
Singapore is a diamond-shaped island with surrounding smaller islands. There are two connections from Singapore to the Malaysian state of Johor — a man-made causeway (known as the Causeway) to the north, crossing the Tebrau Straits, and Tuas Second Link (called Linkedua Expressway in Malaysia), a bridge in the western part of Singapore that connects to Johor.
Of Singapore's dozens of smaller islands, Jurong Island, Pulau Tekong, Pulau Ubin and Sentosa are the larger ones. The highest point of Singapore is Bukit Timah Hill, with a height of 164 m (538 feet).
Bukit Timah Hill]]
The urban area used to be concentrated on the southern part of Singapore around the mouth of the Singapore River, while the rest of the land was tropical rain forest or used for agriculture. Since the 1960s, the government has constructed new towns in outlying areas, resulting in an entirely built-up and urban landscape with a few exceptions, such as the Bukit Timah Nature Reserve. In addition, Singapore has reclaimed land with earth obtained from its own hills, the seabed and neighbouring countries. As a result, Singapore's land area grew from 581.5 km² in the 1960s to 697.2 km² today, and may grow by another 100 km² by 2030.
Without natural freshwater rivers and lakes, the primary domestic source of water in Singapore is rainfall, collected in reservoirs or catchment areas. Rainfall supplies approximately 50% of Singapore's water; the remainder is imported from Malaysia. In addition to existing catchment areas, recycled water facilities (called NEWater) and desalination plants, more NEWater and desalination plants are being built or proposed to reduce reliance on foreign supply.
Singapore has a tropical rainforest climate with no distinct seasons, under the Köppen climate classification. Its climate is characterised by uniform temperature and pressure, high humidity and abundant rainfall. Temperatures range from 23ºC to 35ºC. On average, the relative humidity is around 90 percent in the morning and 60 percent in the afternoon. During prolonged heavy rain, relative humidity often reaches 100 percent.
Economy
relative humidity and hub of economic transactions in Singapore, and is also the home of the Singapore Exchange, Asia-Pacific's first demutualised and integrated securities and derivatives exchange.]]
Singapore has a highly developed market-based economy in which the state plays a major role. It has one of the highest per capita gross domestic products in the world and is considered one of the "East Asian Tigers". Domestic demand is relatively low, and the economy depends heavily on exports produced from refining imported goods in a form of extended entrepot trade. This is especially true in electronics and manufacturing.
Singapore was hit hard in 2001 by the global recession and the slump in the technology sector, which caused the GDP that year to contract by 2.2 percent. The Economic Review Committee (ERC), set up in December 2001, made key recommendations in remaking Singapore's economy.
Singapore introduced the Goods and Services Tax (GST) on April 1, 1994, starting at 3 percent. This has substantially increased government revenue as well assisted in maintaining the stability of the government's finances to spend on reforming the economy into more services and value added goods instead of relying on electronics manufacturing. The taxable GST is now at 5 percent, with the last increase in 2004.
The economy has since recovered in response to improvements in the world economy, and grew by 8.4 percent in 2004. In the longer term the government hopes to establish a new growth path that will be less vulnerable to the external business cycle than the current export-led model, but is unlikely to abandon efforts to establish Singapore as Southeast Asia's financial and high-tech hub. The per capita GDP in 2005 is US$28,228. Recently, in September 2005, the unemployment rate was 3.3 percent.
Tourism
value added
:
Singapore as a travel destination has become noted among many international travellers, making tourism one of the largest industries in Singapore. Much of its attraction can be attributed to its cultural diversity that reflects its rich colonial history and Chinese, Malay, Indian, Eurasian and Arab ethnicities. For many years considered to be the business hub of Southeast Asia, Singapore has an expansive shopping precinct located in the Orchard Road district. Filled with many multi-story shopping centres, the area also has many hotels, and is centre of tourism in Singapore, as opposed to Raffles Place, which can be thought of as the financial heart.
Other popular tourist attractions include the Singapore Zoological Gardens and its Night Safari, which allows people to explore Asian, African and American habitats at night, without any visible barriers between guests and the wild animals. The Singapore Zoo has embraced the 'open zoo' concept whereby animals are kept in enclosures, separated from visitors by hidden dry or wet moats, instead of caging the animals. Also famous is the Jurong Bird Park, wherein there are specimens of magnificent bird life from around the world, including a flock of one thousand flamingos. The tourist island of Sentosa, located in the south of Singapore, consists of about 20-30 landmarks, such as Fort Siloso, which was built as a fortress to defend against the Japanese during World War II. Guns from the World War II era can be seen at Fort Siloso, from a mini-sized to a 16-pound (7 kg) gun. Recently, the island has built the Carlsberg Sky Tower, which allows visitors to view the whole of Sentosa, as well as the Sentosa Luge, a small one- or two-person sled on which one sleighs supine and feet-first. Steering is done by shifting the weight or pulling straps attached to the sled's runners. Singapore will have two integrated resorts with casinos in 2009, one at Marina Bayfront and the other at Sentosa which the government announced during a parliament session on April 18, 2005.
Transport
2005 (MRT) system, one of three heavy rail passenger transport lines in Singapore.]]
Singapore is a major transport hub in Asia and its history has been closely tied to the growth of its transport industry since its infancy. The transport industry contributes over 10% of gross domestic product despite an increasingly diversified economy.
The Port of Singapore, managed by port operators PSA International and Jurong Port, is the world's busiest in terms of shipping tonnage handled. 1.04 billion gross tons were handled in the year 2004, crossing the one billion mark for the first time in Singapore's maritime history. Singapore also emerged as the top port in terms of cargo tonnage handled with 393 million tonnes of cargo in 2004, surpassing the port in Rotterdam for the first time. Singapore is ranked second globally in terms of containerised traffic with 21.3 million twenty-foot equivalent units handled in 2004, and retains her position as the world's busiest hub for transhipment traffic. She is also the world's biggest bunkering hub with 23.6 million tonnes of bunkers sold in 2004.
Singapore is a major aviation hub and is an important stopover point for the "Kangaroo route" between Australasia and Europe. Singapore Changi Airport has a network of 77 airlines connecting Singapore to 178 cities in 56 countries. It is one of the top five airports in Asia in terms of passengers handled, with 30 million passengers passing through in 2004. It has been consistently rated as one of the best international airports by numerous international travel magazines . National carrier Singapore Airlines has also received several accolades internationally and is renowned for the image of the 'Singapore Girl', where air stewardesses are clad in traditional dress (Sarong Kebaya) while serving passengers. It will also be the first airline in the world to fly the new Airbus A380 commercially. In anticipation of rising demand in both the regular and low-cost sectors, a third passenger terminal and a low-cost terminal are currently under construction. These will increase the airport's total capacity to 66.7 million passengers annually by 2008.
Domestic transport infrastructure is relatively efficient, and includes the heavy rail passenger Mass Rapid Transit (MRT) system, the North-East Line, an autopilot extension of the MRT, the Light Rapid Transit (LRT) system, an extensive expressway and road system and a nationwide system of taxis and buses. The EZ-Link system allows, contactless smartcards to be used as stored value tickets for use in the public transport systems, and improves the convenience of the systems. Vehicles are subject to toll by an Electronic Road Pricing (ERP) system during hours of heavy road traffic to regulate road usage. Recently, there have been complaints of rising public transport fares but the government asserts that this is due to the increase in global oil prices. Currently, fares are capped at $1.90 (~US$1.10) per ride.
Electronic Road Pricing will allow it to handle up to 66.7 million passengers annually. Also in the pipeline is a new budget airline terminal to serve the rapidly growing budget airline industry.]]
Demographics
Electronic Road Pricing is the largest Hindu temple in Singapore. It is also one of the many religious buildings marked as national monuments for their historical value.]]
:
Singapore is the second most densely populated independent country in the world. Eighty-four percent of Singaporeans live in public housing provided by the Housing and Development Board (HDB).
Singapore's population, though small at 4.42 million as of July 2005, is relatively diverse compared to most other countries, although neighbour Malaysia also features a multiracial population. The Chinese, who have constituted the majority of the island population since the colonial era, account for 76.8 percent of Singaporeans. Malays, who are the indigenous native group of the country, constitute 13.9 percent, though this number includes many Malay ethnic groups from other parts of the Malay archipelago including the Javanese, Bugis, Baweans and Minangs. Indians are the third largest ethnic group at 7.9 percent, consisting of several groups—Tamils, who form the largest Indian group, and others such as Malayalees, Punjabis and Bengalis. The rest are made up of smaller groups such as Arabs, Jews, Thais, Japanese, and the Eurasian community.
Singapore is generally a multi-religious country, mainly due to its strategic location and the variety of religious beliefs that most Singaporeans hold. More than 40 percent of Singaporeans profess that they adhere to Buddhism. This is usually due to a lack of distinction between Taoism and Buddhism. Taoism, Confucianism, Buddhism, and ancestral worship are merged into one by most of the Chinese population. Most Muslims are Malay but there are adherents among all races. Christianity in Singapore consists of Roman Catholicism and various denominations and its numbers hover at around 14% of the population.
The government of Singapore has been careful to maintain ethnic harmony after racial riots erupted in the 1960s. Racial harmony has been emphasized in all aspects of society, including education, military and housing. So far the policy has been largely successful, and there have been few signs of ethnic tension since the early 1970s. Current issues include the ban on wearing the Islamic headscarf in public schools. In October 2005, a man was sentenced to one month in jail for making racist comments on an online blog.
The national language of Singapore is Malay for historical reasons, and it is used in the national anthem. The official languages are English, Mandarin, Malay and Tamil. English has been promoted as the country's language of administration since independence, and it is spoken by the majority of the population, although with concurrent Speak Mandarin Campaigns, most public signs, advertising and print media tend to be in English and Chinese only.
To promote Chinese culture and the use of Mandarin among the Chinese, the government has introduced a Speak Mandarin Campaign (SMC). Historically, the Chinese immigrants often did not understand each other, having migrated from different parts of | | |
