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3N1! Jiayou!!^^
Date : Friday, May 14, 2010
Time : 10:58 PM
Title :
Time : 10:58 PM
Title :
LIMSERYANG
Date :
Time : 10:54 PM
Title :
Time : 10:54 PM
Title :
Paper chromatography is an analytical chemistry technique for separating and identifying mixtures that are or can be coloured, especially pigments. This can also be used in secondary or primary colours in ink experiments. This method has been largely replaced by thin layer chromatography, however it is still a powerful teaching tool.
INK CHROMATOGRAPHY
Chromatography is a method of separating out materials from a mixture. Ink is a mixture of several dyes and therefore we can separate those colors from one another using chromatography. When ink is exposed to certain solvents the colors dissolve and can be seperated out. When we expose a piece of paper with ink on it to a solvent, the ink spreads across the paper when the ink dissolves.
CANDY CHROMATOGRAPHY
Ever wondered why candies are different colors? Many candies contain colored dyes. Bags of M&Ms or Skittles contain candies of various colors. The labels tell us the names of the dyes used in the candies. But which dyes are used in which candies? We can answer this by dissolving the dyes out of the candies and separating them using a method called chromatography.
LIMSERYANG
INK CHROMATOGRAPHY
Chromatography is a method of separating out materials from a mixture. Ink is a mixture of several dyes and therefore we can separate those colors from one another using chromatography. When ink is exposed to certain solvents the colors dissolve and can be seperated out. When we expose a piece of paper with ink on it to a solvent, the ink spreads across the paper when the ink dissolves.
CANDY CHROMATOGRAPHY
Ever wondered why candies are different colors? Many candies contain colored dyes. Bags of M&Ms or Skittles contain candies of various colors. The labels tell us the names of the dyes used in the candies. But which dyes are used in which candies? We can answer this by dissolving the dyes out of the candies and separating them using a method called chromatography.
LIMSERYANG
Date :
Time : 10:44 PM
Title :
Time : 10:44 PM
Title :
LIMSERYANG 3N1
Date : Wednesday, May 5, 2010
Time : 4:15 PM
Title : Chromatography: Wet Erase Marker in Water
Time : 4:15 PM
Title : Chromatography: Wet Erase Marker in Water
Aaron (34)
Date :
Time : 4:10 PM
Title :
Time : 4:10 PM
Title :
Aaron (34)
Date : Thursday, April 29, 2010
Time : 10:10 PM
Title :
Time : 10:10 PM
Title :
Chromatography is a feasible method to separate the bucket of mixed paint.Advantages of Paper Chromatography:Why use paper chromatography? In a nutshell, this analytical method is quick to perform and easy to master. With a correctly chosen mobile phase (chromatographic solvent), an analyst can rapidly determine the number of constituents of a mixture sample. Sometimes, paper chromatography even allows one to positively identify these constituents. Another advantage of this method is that it requires a relatively small sample and is very inexpensive - a big plus in today's cost-conscious world.Disadvantages of Paper Chromatography:Like all analytical methods, paper chromatography has its limitations. Some mixtures are very difficult to separate by paper chromatography; and any species that is not coloured is difficult to observe on the chromatogram. Also, paper chromatography is solely an analytical method, not a preparative one. Because the sample size is so small, it is difficult to perform further analysis after the sample's contents have been chromatographically separated. This is in contrast to methods such as column chromatography, which are frequently use to preparatively separate larger amounts of mixtures. Lastly, paper chromatography can only be used in qualitative analysis. It is not possible to extract meaningful information about the quantitative content of a mixture from a paper chromatogram.http://www.chem.ubc.ca/courseware/121/tutorials/exp3A/paperchrom/
Paper Chromatography
column chromatography
Gas Chromatography
High performance liquid chromatography
Ultra High Pressure Liquid Chromatography
Thin layer Chromatographyion exchange Chromatography
By Joey.
Paper Chromatography
column chromatography
Gas Chromatography
High performance liquid chromatography
Ultra High Pressure Liquid Chromatography
Thin layer Chromatographyion exchange Chromatography
By Joey.
Date :
Time : 9:11 PM
Title : Paper Chromatography
Time : 9:11 PM
Title : Paper Chromatography
What are the uses of paper chromatography?
They are used in many scientific studies to identify unknown organic and inorganic compounds. They are also used in crime scene investigation, DNA and RNA sequencing, among others. Essentially, any solution can be separated through some form of chromatography. They are used in many scientific studies to identify unknown organic and inorganic compounds. They are also used in crime scene investigation, DNA and RNA sequencing, among others. Essentially, any solution can be separated through some form of chromatography.Why do you need filter paper for the chromatography?
Compare to other papers filter paper is easily absorb or diffusion of solvent is very high and it will helpful to separate the molecules based on the molecular weight.Disadvantages of using paper chromatography?
These are some disadvantages of using paper chromatography: It can be used as a preparative technique because we can't apply a large sample quantity. It can't be used in quantitative analysis and doesn't allow the separation of complex mixtures.
Candy Chromatography(http://www.youtube.com/watch?v=9Oy98D6if1c&feature=related)
Ever wondered why candies are different colors? Many candies contain colored dyes. Bags of M&Ms or Skittles contain candies of various colors. The labels tell us the names of the dyes used in the candies. But which dyes are used in which candies? We can answer this by dissolving the dyes out of the candies and separating them using a method called chromatography.
For this experiment you will need:
• M&M or Skittles candies (1 of each color)
• coffee filter paper
• a tall glass
• water
• table salt
• a pencil(a pen or marker is not good for this experiment)
• scissors
• a ruler
• 6 toothpicks
• aluminum foil
• an empty 2 liter bottle with cap
Cut the coffee filter paper into a 3 inch by 3 inch (8 cm by 8 cm) square. Draw a line with the pencil about ½ inch (1 cm) from one edge of the paper. Make six dots with the pencil equally spaced along the line, leaving about ¼ inch (0.5 cm) between the first and last dots and the edge of the paper. Below the line, use the pencil to label each dot for the different colors of candy that you have. For example, Y for yellow, G for green, BU for blue, BR for brown, etc.
Next we’ll make solutions of the colors in each candy. Take an 8 inch by 4 inch (20 cm by 10 cm) piece of aluminum foil and lay it flat on a table. Place six drops of water spaced evenly along the foil. Place one color of candy on each drop. Wait about a minute for the color to come off the candy and dissolve in the water. Remove and dispose of the candies.
Now we’ll “spot” the colors onto the filter paper. Dampen the tip of one of the toothpicks in one of the colored solutions and lightly touch it to the corresponding labeled dot on your coffee filter paper. Use a light touch, so that the dot of color stays small - less than 1/16 inch (2 mm) is best. Then using a different toothpick for each color, similarly place a different color solution on each of the other five dots.
After all the color spots on the filter paper have dried, go back and repeat the process with the toothpicks to get more color on each spot. Do this three times, waiting for the spots to dry each time.
When the paper is dry, fold it in half so that it stands up on its own, with the fold standing vertically and the dots on the bottom.
Next we will make what is called a developing solution. Make sure your 2-liter bottle or milk jug is rinsed out, and add to it ⅛ teaspoon of salt and three cups of water (or use 1 cm3 of salt and 1 liter of water). Then screw the cap on tightly and shake the contents until all of the salt is dissolved in the water. You have just made a 1% salt solution.
Now pour the salt solution into the tall glass to a depth of about ¼ inch (0.5 cm). The level of the solution should be low enough so that when you put the filter paper in, the dots will initially be above the water level. Hold the filter paper with the dots at the bottom and set it in the glass with the salt solution.
What does the salt solution do? It climbs up the paper! It seems to defy gravity, while in fact it is really moving through the paper by a process called capillary action.
As the solution climbs up the filter paper, what do you begin to see?
The color spots climb up the paper along with the salt solution, and some colors start to separate into different bands. The colors of some candies are made from more than one dye, and the colors that are mixtures separate as the bands move up the paper. The dyes separate because some dyes stick more to the paper while other dyes are more soluble in the salt solution. These differences will lead to the dyes ending up at different heights on the paper.
This process is called chromatography. (The word “chromatography” is derived from two Greek words: "chroma" meaning color and "graphein" to write.) The salt solution is called the mobile phase, and the paper the stationary phase. We use the word “affinity” to refer to the tendency of the dyes to prefer one phase over the other. The dyes that travel the furthest have more affinity for the salt solution (the mobile phase); the dyes that travel the least have more affinity for the paper (the stationary phase).
When the salt solution is about ½ inch (1 cm) from the top edge of the paper, remove the paper from the solution. Lay the paper on a clean, flat surface to dry.
Compare the spots from the different candies, noting similarities and differences. Which candies contained mixtures of dyes? Which ones seem to have just one dye? Can you match any of the colors on the paper with the names of the dyes on the label? Do similar colors from different candies travel up the paper the same distance?
You can do another experiment with a different type of candy. If you used Skittles the first time, repeat the experiment with M&Ms. If you used M&Ms first, try doing the experiment with Skittles. Do you get the same results for the different kinds of candy, or are they different? For example, do green M&Ms give the same results as green Skittles?
You can also use chromatography to separate the colors in products like colored markers, food coloring, and Kool-Aid. Try the experiment again using these products. What similarities and differences do you see?
Date :
Time : 8:56 PM
Title : Chemistry;DD----Eugene
Time : 8:56 PM
Title : Chemistry;DD----Eugene
1) Is Chromatography A Feasible Method To Seperate The Bucket Of Mixed Paint?
Yes.. It Is A Feasible Method As Chromatography Is Fast High-Performance Liquid Chromatography Coupled To Electrosprayed Ioninzation Mass Spectrometry In The Selected Ion Monitering Mode For The Quantitative Determination Of Aspatic Acid In An Asparate Drug.
2)What Are The Advantage And Disadvantage Of Chromatography?
Advantage: - It Is Very Accurate And Fast
- The Cost Of Buying The Chromatography Paper Is Less Expensive
- It Can Be Easily Used By Food Inspector/Customs To Test The Food Contain Illegal Materials e.g Drugs
Disadvantage: - Not All Types Of Illegal Materials Can Be Analyzed Or Conclude By The Chromatography Method
3) What Are The Different Type Of Chromatography There Are?
They Are Lots Of Type Of Chromatograpy--- Column Chromatography, Planer Chromatography, Thin Layer Chromatography, Displacement Chromatography , Gas Chromatography, Affinity Chromatography And Liquid Chromatography
------------The End------------------- Eugene Tan 3n1-Chromatography;DD
Yes.. It Is A Feasible Method As Chromatography Is Fast High-Performance Liquid Chromatography Coupled To Electrosprayed Ioninzation Mass Spectrometry In The Selected Ion Monitering Mode For The Quantitative Determination Of Aspatic Acid In An Asparate Drug.
2)What Are The Advantage And Disadvantage Of Chromatography?
Advantage: - It Is Very Accurate And Fast
- The Cost Of Buying The Chromatography Paper Is Less Expensive
- It Can Be Easily Used By Food Inspector/Customs To Test The Food Contain Illegal Materials e.g Drugs
Disadvantage: - Not All Types Of Illegal Materials Can Be Analyzed Or Conclude By The Chromatography Method
3) What Are The Different Type Of Chromatography There Are?
They Are Lots Of Type Of Chromatograpy--- Column Chromatography, Planer Chromatography, Thin Layer Chromatography, Displacement Chromatography , Gas Chromatography, Affinity Chromatography And Liquid Chromatography
------------The End------------------- Eugene Tan 3n1-Chromatography;DD
Date :
Time : 4:14 PM
Title :
Time : 4:14 PM
Title :
http://www.youtube.com/watch?v=Vj_o7NuBA2I -Tan Chai Ming
Date :
Time : 3:23 PM
Title :
Time : 3:23 PM
Title :
1) Is chromatography a feasible method to separate the bucket of mixed paint?
Yes, it is a feasible method.
2) What are the advantages and disadvantages of chromatography?
Advantage:
1)More accurate and faster.
2)Cost lesser.
3)Help the government find out if the food contain illegal materials.
Disadvantage:
1)Some mixtures are very difficult to separate.
3)What are the different types of chromatography there are?
Column chromatography,Planar chromatography,
Thin layer chromatography,Displacement chromatography,
Gas chromatography,Liquid chromatography,
Affinity chromatography
http://www.youtube.com/watch?v=uxP9qwpUBBU
NICHOLAS TAN 3N1
Date :
Time : 2:13 PM
Title : Paper Chromatography
Time : 2:13 PM
Title : Paper Chromatography
1) Is chromatography a feasible method to separate the bucket of mixed paint?
= Yes, it is a feasible method.
2) What are the advantages and disadvantages of chromatography?
= The advantages are it can separate and identify mixtures that are or can be coloured and especially pigments. The disadvantages are that some mixtures are very difficult to separate by paper chromatography and any species that is not coloured is difficult to observe the chromatorgram.
3)What are the different types of chromatography there are?
= Column chromatography, Thin layer chromatography, Gas chromatography.
SRI SYAZWANI [15]
Date : Saturday, April 24, 2010
Time : 8:17 PM
Title :
Time : 8:17 PM
Title :
-Tan Chai Ming
Date : Friday, April 23, 2010
Time : 5:33 PM
Title :
Time : 5:33 PM
Title :
1)Is chromatography a feasible method to seperate the bucket of mixed paint?
Yes,it is a feasible method.
2)What are the advantages and disadvantages of chromatography?
Avantages:It is less expensive and it can seperate and identify mixtures, colours and dyes.
Disadvantages:Some mixtures are difficult to seperate by paper chromatography.
For more info about paper chromatography go to the link:http://www.youtube.com/watch?v=Oy_yTOwyRLM
Yes,it is a feasible method.
2)What are the advantages and disadvantages of chromatography?
Avantages:It is less expensive and it can seperate and identify mixtures, colours and dyes.
Disadvantages:Some mixtures are difficult to seperate by paper chromatography.
For more info about paper chromatography go to the link:http://www.youtube.com/watch?v=Oy_yTOwyRLM
Date : Wednesday, April 21, 2010
Time : 8:18 PM
Title :
Time : 8:18 PM
Title :
1)Is chromatography a feasible method to seperate the bucket of mixed paint?
Yes,it is a feasible method.
2)What are the advantages and disadvantages of chromatography?
Avantages:It is less expensive.It is faster and more accurate.It can seperate and identify mixtures,colours and dyes.
Disadvantages:Some mixtures are difficult to seperate by paper chromatography.
3)Different types of chromatography:Paper,Gas,Liquid,Affinity,Ion exchange,Thin layer,Column.
-SONAM (14) 3N1
Date :
Time : 7:17 PM
Title : Zhenghan (32)
Time : 7:17 PM
Title : Zhenghan (32)
Heat transfer:
Heat transfer is the transition of thermal energy from a hotter mass to a cooler mass. When an object is at a different temperature than its surroundings or another object, transfer of thermal energy, also known as heat flow, or heat exchange, occurs in such a way that the body and the surroundings reach thermal equilibrium; this means that they are at the same temperature. Heat transfer always occurs from a higher-temperature object to a cooler-temperature one as described by the second law of thermodynamics or the Clausius statement. Where there is a temperature difference between objects in proximity, heat transfer between them can never be stopped; it can only be slowed.
Convection:
Convection is the transfer of thermal energy by the movement of molecules from one part of the material to another. As the fluid motion increases, so does the convective heat transfer. The presence of bulk motion of the fluid enhances the heat transfer between the solid surface and the fluid.
Conduction:
Conduction is the transfer of heat by direct contact of particles of matter. The transfer of energy could be primarily by elastic impact as in fluids or by free electron diffusion as predominant in metals or phonon vibration as predominant in insulators. In other words, heat is transferred by conduction when adjacent atoms vibrate against one another, or as electrons move from one atom to another. Conduction is greater in solids, where a network of relatively fixed spacial relationships between atoms helps to transfer energy between them by vibration.
Radiation:
Radiation is the transfer of heat energy through empty space. All objects with a temperature above absolute zero radiate energy at a rate equal to their emissivity multiplied by the rate at which energy would radiate from them if they were a black body. No medium is necessary for radiation to occur, for it is transferred through electromagnetic waves; radiation works even in and through a perfect vacuum. The energy from the Sun travels through the vacuum of space before warming the earth.
Heat transfer:
Heat transfer is the transition of thermal energy from a hotter mass to a cooler mass. When an object is at a different temperature than its surroundings or another object, transfer of thermal energy, also known as heat flow, or heat exchange, occurs in such a way that the body and the surroundings reach thermal equilibrium; this means that they are at the same temperature. Heat transfer always occurs from a higher-temperature object to a cooler-temperature one as described by the second law of thermodynamics or the Clausius statement. Where there is a temperature difference between objects in proximity, heat transfer between them can never be stopped; it can only be slowed.
Convection:
Convection is the transfer of thermal energy by the movement of molecules from one part of the material to another. As the fluid motion increases, so does the convective heat transfer. The presence of bulk motion of the fluid enhances the heat transfer between the solid surface and the fluid.
Conduction:
Conduction is the transfer of heat by direct contact of particles of matter. The transfer of energy could be primarily by elastic impact as in fluids or by free electron diffusion as predominant in metals or phonon vibration as predominant in insulators. In other words, heat is transferred by conduction when adjacent atoms vibrate against one another, or as electrons move from one atom to another. Conduction is greater in solids, where a network of relatively fixed spacial relationships between atoms helps to transfer energy between them by vibration.
Radiation:
Radiation is the transfer of heat energy through empty space. All objects with a temperature above absolute zero radiate energy at a rate equal to their emissivity multiplied by the rate at which energy would radiate from them if they were a black body. No medium is necessary for radiation to occur, for it is transferred through electromagnetic waves; radiation works even in and through a perfect vacuum. The energy from the Sun travels through the vacuum of space before warming the earth.
Heat transfer:
Date :
Time : 3:01 PM
Title :
Time : 3:01 PM
Title :
Date :
Time : 2:57 PM
Title :
Time : 2:57 PM
Title :
1) Is chromatography a feasible method to separate the bucket of mixed paint?- Yes, it is a feasible method.
2) What are the advantages and disadvantages of chromatography?
- The advantages are it can separate and identify mixtures that are or can be coloured and especially pigments. The disadvantages are that some mixtures are very difficult to separate by paper chromatography and any species that is not coloured is difficult to observe the chromatorgram.
3)What are the different types of chromatography there are?
- Column chromatography, Thin layer chromatography, Gas chromatography.
- Amalina
Date :
Time : 10:08 AM
Title : Physics - Thermal Energy
Time : 10:08 AM
Title : Physics - Thermal Energy
Thermal energy
Thermal energy is generated and measured by heat of any kind. It is caused by the increased activity or velocity of molecules in a substance, which in turn causes temperature to rise accordingly.
Conduction:
In heat transfer, conduction (or heat conduction) is the transfer of thermal energy between neighboring molecules in a substance due to a temperature gradient. It always takes place from a region of higher temperature to a region of lower temperature, and acts to equalize temperature differences. Conduction takes place in all forms of matter, viz. solids, liquids, gases and plasmas, but does not require any bulk motion of matter. In solids, it is due to the combination of vibrations of the molecules in a lattice and the energy transport by free electrons. In gases and liquids, conduction is due to the collisions and diffusion of the molecules during their random motion.
Convection:
Convection is the movement of molecules within fluids (i.e. liquids, gases and solids). It cannot take place in solids, since neither bulk current flows or significant diffusion can take place in solids.
Radiation:
Radiation is the transfer of energy by electromagnetic waves.
For a simple animation, please go to this website...
http://www.youtube.com/watch?v=wz6wzOtv6rs
Thermal energy is generated and measured by heat of any kind. It is caused by the increased activity or velocity of molecules in a substance, which in turn causes temperature to rise accordingly.
Conduction:
In heat transfer, conduction (or heat conduction) is the transfer of thermal energy between neighboring molecules in a substance due to a temperature gradient. It always takes place from a region of higher temperature to a region of lower temperature, and acts to equalize temperature differences. Conduction takes place in all forms of matter, viz. solids, liquids, gases and plasmas, but does not require any bulk motion of matter. In solids, it is due to the combination of vibrations of the molecules in a lattice and the energy transport by free electrons. In gases and liquids, conduction is due to the collisions and diffusion of the molecules during their random motion.
Convection:
Convection is the movement of molecules within fluids (i.e. liquids, gases and solids). It cannot take place in solids, since neither bulk current flows or significant diffusion can take place in solids.
Radiation:
Radiation is the transfer of energy by electromagnetic waves.
For a simple animation, please go to this website...
http://www.youtube.com/watch?v=wz6wzOtv6rs
Labels: DOne by zulfiqar(37)
Date :
Time : 10:03 AM
Title : Heat Transfer 1944
Time : 10:03 AM
Title : Heat Transfer 1944
izzati 3n1
Date :
Time : 10:01 AM
Title :
Time : 10:01 AM
Title :
Sound as a Longitudinal Wave
In the first part of Lesson 1, it was mentioned that sound is a mechanical wave which is created by a vibrating object. The vibrations of the object set particles in the surrounding medium in vibrational motion, thus transporting energy through the medium. For a sound wave traveling through air, the vibrations of the particles are best described as longitudinal. Longitudinal waves are waves in which the motion of the individual particles of the medium is in a direction which is parallel to the direction of energy transport. A longitudinal wave can be created in a slinky if the slinky is stretched out in a horizontal direction and the first coils of the slinky are vibrated horizontally. In such a case, each individual coil of the medium is set into vibrational motion in directions parallel to the direction which the energy is transported.
Sound waves in air (and any fluid medium) are longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction which the sound wave moves. A vibrating string can create longitudinal waves as depicted in the animation below. As the vibrating string moves in the forward direction, it begins to push upon surrounding air molecules, moving them to the right towards their nearest neighbor. This causes the air molecules to the right of the string to be compressed into a small region of space. As the vibrating string moves in the reverse direction (leftward), it lowers the pressure of the air immediately to its right, thus causing air molecules to move back leftward. The lower pressure to the right of the string causes air molecules in that region immediately to the right of the string to expand into a large region of space. The back and forth vibration of the string causes individual air molecules (or a layer of air molecules) in the region immediately to the right of the string to continually vibrate back and forth horizontally. The molecules move rightward as the string moves rightward and then leftward as the string moves leftward. These back and forth vibrations are imparted to adjacent neighbors by particle-to-particle interaction. Other surrounding particles begin to move rightward and leftward, thus sending a wave to the right. Since air molecules (the particles of the medium) are moving in a direction which is parallel to the direction which the wave moves, the sound wave is referred to as a longitudinal wave. The result of such longitudinal vibrations is the creation of compressions and rarefactions within the air.
Regardless of the source of the sound wave - whether it be a vibrating string or the vibrating tines of a tuning fork - sound waves traveling through air are longitudinal waves. And the essential characteristic of a longitudinal wave which distinguishes it from other types of waves is that the particles of the medium move in a direction parallel to the direction of energy transport.
cassandra
In the first part of Lesson 1, it was mentioned that sound is a mechanical wave which is created by a vibrating object. The vibrations of the object set particles in the surrounding medium in vibrational motion, thus transporting energy through the medium. For a sound wave traveling through air, the vibrations of the particles are best described as longitudinal. Longitudinal waves are waves in which the motion of the individual particles of the medium is in a direction which is parallel to the direction of energy transport. A longitudinal wave can be created in a slinky if the slinky is stretched out in a horizontal direction and the first coils of the slinky are vibrated horizontally. In such a case, each individual coil of the medium is set into vibrational motion in directions parallel to the direction which the energy is transported.
Sound waves in air (and any fluid medium) are longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction which the sound wave moves. A vibrating string can create longitudinal waves as depicted in the animation below. As the vibrating string moves in the forward direction, it begins to push upon surrounding air molecules, moving them to the right towards their nearest neighbor. This causes the air molecules to the right of the string to be compressed into a small region of space. As the vibrating string moves in the reverse direction (leftward), it lowers the pressure of the air immediately to its right, thus causing air molecules to move back leftward. The lower pressure to the right of the string causes air molecules in that region immediately to the right of the string to expand into a large region of space. The back and forth vibration of the string causes individual air molecules (or a layer of air molecules) in the region immediately to the right of the string to continually vibrate back and forth horizontally. The molecules move rightward as the string moves rightward and then leftward as the string moves leftward. These back and forth vibrations are imparted to adjacent neighbors by particle-to-particle interaction. Other surrounding particles begin to move rightward and leftward, thus sending a wave to the right. Since air molecules (the particles of the medium) are moving in a direction which is parallel to the direction which the wave moves, the sound wave is referred to as a longitudinal wave. The result of such longitudinal vibrations is the creation of compressions and rarefactions within the air.
Regardless of the source of the sound wave - whether it be a vibrating string or the vibrating tines of a tuning fork - sound waves traveling through air are longitudinal waves. And the essential characteristic of a longitudinal wave which distinguishes it from other types of waves is that the particles of the medium move in a direction parallel to the direction of energy transport.
cassandra
Date :
Time : 10:00 AM
Title : Thermal energy
Time : 10:00 AM
Title : Thermal energy
Heat transfer is the transition of thermal energy from a hotter mass to a cooler mass. When an object is at a different temperature than its surroundings or another object, transfer of thermal energy, also known as heat flow, or heat exchange, occurs in such a way that the body and the surroundings reach thermal equilibrium; this means that they are at the same temperature. Heat transfer always occurs from a higher-temperature object to a cooler-temperature one as described by the second law of thermodynamics or the Clausius statement. Where there is a temperature difference between objects in proximity, heat transfer between them can never be stopped; it can only be slowed.
Izzati 3N1
Izzati 3N1
Date :
Time : 9:59 AM
Title :
Time : 9:59 AM
Title :
Types of wave
There are various ways of classifying wave types. One of these is based on the way the wave travels. In a transverse wave, the displacement of the medium is perpendicular to the direction in which the wave travels. An example of this type of wave is a mechanical wave projected along a tight string. The string moves at right angles to the wave motion. Electromagnetic waves are another example of transverse waves. The directions of the electric and magnetic fields are perpendicular to the wave motion. In a longitudinal wave the disturbance takes place parallel to the wave motion. A longitudinal wave consists of a series of compressions and rarefactions (states of maximum and minimum density and pressure, respectively). Such waves are always mechanical in nature and thus require a medium through which to travel. Sound waves are an example of longitudinal waves. Waves that result from a stone being dropped into water appear as a series of circles. These are called circular waves and can be generated in a ripple tank for study. Waves on water that appear as a series of parallel lines are called plane waves.
Characteristics of waves
All waves have a wavelength. This is measured as the distance between successive crests (or successive troughs) of the wave. It is given the Greek symbol λ. The frequency of a wave is the number of vibrations per second. It is expressed in hertz, symbol Hz (1 Hz = 1 cycle per second). The reciprocal of this is the wave period. This is the time taken for one complete cycle of the wave oscillation. The speed of the wave is measured by multiplying wave frequency by the wavelength.
Properties of waves
When a wave moves from one medium to another (for example a light wave moving from air to glass) it moves with a different speed in the second medium. This change in speed causes it to change direction. This property is called refraction. The angle of refraction depends on whether the wave is speeding up or slowing down as it changes medium. Reflection occurs whenever a wave hits a barrier. The wave is sent back, or reflected, into the medium. The angle of incidence (the angle between the ray and a perpendicular line drawn to the surface) is equal to the angle of reflection (the angle between the reflected ray and a perpendicular to the surface). See also total internal reflection. An echo is the repetition of a sound wave by reflection from a surface. All waves spread slightly as they travel. This is called diffraction and it occurs chiefly when a wave interacts with a solid object. The degree of diffraction depends on the relationship between the wavelength and the size of the object (or gap through which the wave travels). If the two are similar in size, diffraction occurs and the wave can be seen to spread out. Large objects cast shadows because the difference between their size and the wavelength is so large that light waves are not diffracted around the object. A dark shadow results. When two or more waves meet at a point, they interact and combine to produce a resultant wave of larger or smaller amplitude (depending on whether the combining waves are in or out of phase with each other). This is called interference. Transverse waves can exhibit polarization. If the oscillations of the wave take place in many different directions (all at right angles to the directions of the wave) the wave is unpolarized. If the oscillations occur in one plane only, the wave is polarized. Light, which consists of transverse waves, can be polarized.
Nur Haifah (13)
There are various ways of classifying wave types. One of these is based on the way the wave travels. In a transverse wave, the displacement of the medium is perpendicular to the direction in which the wave travels. An example of this type of wave is a mechanical wave projected along a tight string. The string moves at right angles to the wave motion. Electromagnetic waves are another example of transverse waves. The directions of the electric and magnetic fields are perpendicular to the wave motion. In a longitudinal wave the disturbance takes place parallel to the wave motion. A longitudinal wave consists of a series of compressions and rarefactions (states of maximum and minimum density and pressure, respectively). Such waves are always mechanical in nature and thus require a medium through which to travel. Sound waves are an example of longitudinal waves. Waves that result from a stone being dropped into water appear as a series of circles. These are called circular waves and can be generated in a ripple tank for study. Waves on water that appear as a series of parallel lines are called plane waves.
Characteristics of waves
All waves have a wavelength. This is measured as the distance between successive crests (or successive troughs) of the wave. It is given the Greek symbol λ. The frequency of a wave is the number of vibrations per second. It is expressed in hertz, symbol Hz (1 Hz = 1 cycle per second). The reciprocal of this is the wave period. This is the time taken for one complete cycle of the wave oscillation. The speed of the wave is measured by multiplying wave frequency by the wavelength.
Properties of waves
When a wave moves from one medium to another (for example a light wave moving from air to glass) it moves with a different speed in the second medium. This change in speed causes it to change direction. This property is called refraction. The angle of refraction depends on whether the wave is speeding up or slowing down as it changes medium. Reflection occurs whenever a wave hits a barrier. The wave is sent back, or reflected, into the medium. The angle of incidence (the angle between the ray and a perpendicular line drawn to the surface) is equal to the angle of reflection (the angle between the reflected ray and a perpendicular to the surface). See also total internal reflection. An echo is the repetition of a sound wave by reflection from a surface. All waves spread slightly as they travel. This is called diffraction and it occurs chiefly when a wave interacts with a solid object. The degree of diffraction depends on the relationship between the wavelength and the size of the object (or gap through which the wave travels). If the two are similar in size, diffraction occurs and the wave can be seen to spread out. Large objects cast shadows because the difference between their size and the wavelength is so large that light waves are not diffracted around the object. A dark shadow results. When two or more waves meet at a point, they interact and combine to produce a resultant wave of larger or smaller amplitude (depending on whether the combining waves are in or out of phase with each other). This is called interference. Transverse waves can exhibit polarization. If the oscillations of the wave take place in many different directions (all at right angles to the directions of the wave) the wave is unpolarized. If the oscillations occur in one plane only, the wave is polarized. Light, which consists of transverse waves, can be polarized.
Nur Haifah (13)
Date :
Time : 9:59 AM
Title :
Time : 9:59 AM
Title :
Mukhail
Date :
Time : 9:58 AM
Title : Definition of thermal energy
Time : 9:58 AM
Title : Definition of thermal energy
Thermal energy is generally considered to be a term used in physics, and refers to the energy created when the kinetic and potential energy of an object in motion is combined. As the name implies, thermal energy refers to heat that is created through the process of thermal energy.
Thus, thermal energy can simply be described as a flow of energy, or a means of energy that is moving from one system or state to another. As the energy moves from one state to another, a difference in temperature will occur. This difference in temperature is noted as the thermal energy.
From a physics standpoint, thermal energy for an object is calculated by summing the sensible and latent forms of internal energy within an object. Every object on the planet has what is known as internal energy. Internal energy is the sum of all forms of energy within an object. Every object has the following potential properties of internal energy: sensible energy, latent energy, chemical energy, nuclear energy. Sensible energy refers to the portion of energy of an object that is associated with kinetic energy, whereas latent energy refers to the phase of matter of the object such as solid, liquid, or gas. Thus, thermal energy refers to the combination of sensible and latent energies within an object.
For example, when butter is melted on the stove, it contains kinetic energy by the very fact that the butter is in motion. It also contains latent energy as it moves from one state of matter to another – from solid to liquid. The combination of kinetic energy and latent energy as the butter melts will be the thermal energy, and is generally referred to as the temperature difference between the two states of matter.
Another example of thermal energy lies in the simple calorie. We all know what calories are as we watch them closely when we are on a diet. More calories ingested will ultimately result in weight gain, and thus, calories are a form of energy in themselves. Thermal energy is used to calculate the caloric content of a food item. The amount of energy that is required to raise the temperature of one gram of the food item by one degree is referred to as the caloric content that is calculated through thermal energy. The more thermal energy that is required to raise the temperature of one gram of food, the more calories that food item will have.
YAMAN (33) 3N1
Date :
Time : 9:57 AM
Title :
Time : 9:57 AM
Title :
Longitudinal and Transverse energy waves are the two types.
Transverse wave - A transverse wave is a wave in which the motion of the medium is perpendicular to the motion of the wave.
Longitudinal wave - A longitudinal wave is a wave in which the motion of the medium is parallel to the motion of the wave.
Water waves are mostly transverse. The water moves up and down while the wave travels over the surface of the water.
Sound waves are longitudinal. The air vibrates back and forth along the same direction as the wave is traveling.
BY NABIL 3N1 (29)
Date :
Time : 9:57 AM
Title :
Time : 9:57 AM
Title :
Representing Sound as Pressure Waves
Longitudinal Wave Characteristics Travelling Through Different Media
Sounds are pressure waves reaching our hearing apparatus by the movement of surrounding air molecules. Studying waves helps us to understand basic transport mechanisms.
All sounds are produced by vibrations. A guitar string vibrates and sets forth air molecules into vibratory motion and creates pressure waves, which travel outward from its source. The human hearing apparatus is designed to decode this information, and discriminate between pitch, or frequency, and how loud the sound is.
Waves share some characteristic properties and behaviours (Chapman et al, Heinemann Physics 12, Harcourt Education, 2007). Categorization of waves is according to direction of movement of individual particles of the medium relative to travel direction (see also Fig. 1):
- A transverse wave in which particles of the medium move perpendicular to the direction of the wave.
- A longitudinal wave in which particles of the medium move parallel to the direction of the wave.
Longidutinal Waves
Sound waves are called longitudinal (or compression) waves because particle vibration is in the same direction as the line of travel. Particles do not keep moving forward; that is, sound waves transfer energy without transferring particles, which vibrate back and forth about their equilibrium positions. An applet may be viewed to help visualise this energy transfer process.
Representing Sound as Waves
Longitudinal waves are difficult to visualise, therefore a transverse analogy is used to help with understanding. The following wave properties are defined (see Fig. 2):
- Wavelength, lamda, is the distance between two points undergoing corresponding movement
- Amplitude is the maximum air pressure and relates to the loudness
- Period, T, is the time taken for one complete wave to pass a given point
- Frequency, f, determines the pitch of the sound. The unit is the Hertz, or Hz
There exists an inverse relationship between the period of a soundwave and its frequency, mathematically given by:
Period: T = 1/f
Speed v is distance divided by time. If a distance of one wavelength is divided by the time taken to travel one wavelength (i.e. one period T), then v = lamda / T. Substituting 1/f for the period, wave speed may be written:
Wave speed: v = f x lamda
Sound travels more rapidly through relatively densely packed materials such as liquids and solids compared to gases such as air (for example, speed is 1500 m/s in water and 3500 m/s in brass, but only 340 m/s in air).
Worked Examples
What is the period of a 50 Hz sound source? Period T = 1/f = 1/50 = 0.02 s (or 20 ms).
What is the wavelength of sound with frequency 500 Hz, travelling through air at 340 m/s? Making lamda the subject: lamda = v / f = 340/500 = 0.68 m.
Frequency and the Medium
Whilst the speed of sound will vary depending on the medium through which it travels, its frequency will remain constant. Only by changing the source of the vibration will the frequency change.
For a fixed medium, the wave speed equation may written as v = f x lamda = constant. Therefore changing source frequency must have the effect of changing wavelength (and vice versa), so as to keep the speed constant. This means that:
Rule: Frequency is inversely proportional to Wavelength
For example in music,
- bass sounds have low frequencies or long wavelengths in air, and
- treble sounds have higher frequencies or shorter wavelengths in air.
Summary
Sounds may be thought of as longitudinal pressure waves. It is useful to study waves to help with our understanding of energy transport from the source to the human receiver. Speed of sound depends on the medium in which it travels but the sound's frequency depends only on the vibration of the source itself.
The reader may be interested in more details on this topic or to learn about the diffraction of sound waves.
The copyright of the article Representing Sound as Pressure Waves in Physics is owned by Harry P. Schlanger. Permission to republish Representing Sound as Pressure Waves in print or online must be granted by the author in writing.
 Notes |  Fig 1. Type of Waves |  Fig 2. Wave Properties |
cassandra
Date :
Time : 9:55 AM
Title :
Time : 9:55 AM
Title :
Convection is the transfer of heat by the actual movement of the warmed matter. Heat leaves the coffee cup as the currents of steam and air rise. Convection is the transfer of heat energy in a gas or liquid by movement of currents. (It can also happen is some solids, like sand.) The heat moves with the fluid. Consider this: convection is responsible for making macaroni rise and fall in a pot of heated water. The warmer portions of the water are less dense and therefore, they rise. Meanwhile, the cooler portions of the water fall because they are denser.
Conduction is the transfer of energy through matter from particle to particle. It is the transfer and distribution of heat energy from atom to atom within a substance. For example, a spoon in a cup of hot soup becomes warmer because the heat from the soup is conducted along the spoon. Conduction is most effective in solids-but it can happen in fluids. Fun fact: Have you ever noticed that metals tend to feel cold? Believe it or not, they are not colder! They only feel colder because they conduct heat away from your hand. You perceive the heat that is leaving your hand as cold.
Radiation: Electromagnetic waves that directly transport ENERGY through space. Sunlight is a form of radiation that is radiated through space to our planet without the aid of fluids or solids. The energy travels through nothingness! Just think of it! The sun transfers heat through 93 million miles of space. Because there are no solids (like a huge spoon) touching the sun and our planet, conduction is not responsible for bringing heat to Earth. Since there are no fluids (like air and water) in space, convection is not responsible for transferring the heat. Thus, radiation brings heat to our planet.
http://www.mansfieldct.org/schools/mms/staff/hand/convcondrad.htm
yuxia
Date :
Time : 9:55 AM
Title :
Time : 9:55 AM
Title :
Mukhail
Date :
Time : 9:55 AM
Title : Transverse and Longitudinal Waves
Time : 9:55 AM
Title : Transverse and Longitudinal Waves
Aaron
Date :
Time : 9:54 AM
Title : WSM = Wave Structure of Matter done by: annisaa
Time : 9:54 AM
Title : WSM = Wave Structure of Matter done by: annisaa
Date :
Time : 9:53 AM
Title : Sound waves(Intan)
Time : 9:53 AM
Title : Sound waves(Intan)
Sound is transmitted through gases, plasma, and liquids as longitudinal waves that have the same direction of oscillation or vibration along their direction of travel while transverse waves (in solids) are waves of alternating shear stress at right angle to the direction of propagation.Sound waves are characterized by the generic properties of waves, which are frequency, wavelength, period, amplitude, intensity, speed, and direction.
- Amplitude: the height of the wave, measured in meters.
- Wavelength: the distance between adjacent crests, measured in meters.
- Period: the time it takes for one complete wave to pass a given point, measured in seconds.
- Frequency: the number of complete waves that pass a point in one second, measured in inverse seconds, or Hertz (Hz).
- Speed: the horizontal speed of a point on a wave as it propagates, measured in meters / second.
Video : http://www.youtube.com/watch?v=Yjz5bcKoogg&feature=related
Intan Nadhirah (5)
Date :
Time : 9:53 AM
Title :
Time : 9:53 AM
Title :
by , SRI SYAZWANI [15 ]
Date :
Time : 9:53 AM
Title : Wave Motion
Time : 9:53 AM
Title : Wave Motion
Aaron
Date :
Time : 9:53 AM
Title : Creating a Longitudinal Wave
Time : 9:53 AM
Title : Creating a Longitudinal Wave
By:Choo Jia Wei
Date :
Time : 9:51 AM
Title : Two types of waves and terms used in waves
Time : 9:51 AM
Title : Two types of waves and terms used in waves
Longitudinal Waves
In a longitudinal wave the particle displacement is parallel to the direction of wave propagation. The animation below shows a one-dimensional longitudinal plane wave propagating down a tube. The particles do not move down the tube with the wave; they simply oscillate back and forth about their individual equilibrium positions. Pick a single particle and watch its motion. The wave is seen as the motion of the compressed region (ie, it is a pressure wave), which moves from left to right.
Transverse Waves
In a transverse wave the particle displacement is perpendicular to the direction of wave propagation. The animation below shows a one-dimensional transverse plane wave propagating from left to right. The particles do not move along with the wave; they simply oscillate up and down about their individual equilibrium positions as the wave passes by. Pick a single particle and watch its motion.
Helmi(27)
Date :
Time : 9:49 AM
Title :
Time : 9:49 AM
Title :
Longitudinal and Transverse Wave Motion
Mechanical Waves are waves which propagate through a material medium (solid, liquid, or gas) at a wave speed which depends on the elastic and inertial properties of that medium. There are two basic types of wave motion for mechanical waves: longitudinal waves and transverse waves. The animations below demonstrate both types of wave and illustrate the difference between the motion of the wave and the motion of the particles in the medium through which the wave is travelling.
[The following animations were created using a modifed version of the Mathematica® Notebook " Sound Waves" by Mats Bengtsson.]
Longitudinal Waves
In a longitudinal wave the particle displacement is parallel to the direction of wave propagation. The animation below shows a one-dimensional longitudinal plane wave propagating down a tube. The particles do not move down the tube with the wave; they simply oscillate back and forth about their individual equilibrium positions. Pick a single particle and watch its motion. The wave is seen as the motion of the compressed region (ie, it is a pressure wave), which moves from left to right.
To see a animations of spherical longitudinal waves check out:
* Sound Radiation from Simple Sources
* Radiation from Cylindrical Sources
Transverse Waves
In a transverse wave the particle displacement is perpendicular to the direction of wave propagation. The animation below shows a one-dimensional transverse plane wave propagating from left to right. The particles do not move along with the wave; they simply oscillate up and down about their individual equilibrium positions as the wave passes by. Pick a single particle and watch its motion.
Water Waves
Water waves are an example of waves that involve a combination of both longitudinal and transverse motions. As a wave travels through the waver, the particles travel in clockwise circles. The radius of the circles decreases as the depth into the water increases. The movie below shows a water wave travelling from left to right in a region where the depth of the water is greater than the wavelength of the waves. I have identified two particles in blue to show that each particle indeed travels in a clockwise circle as the wave passes.
Rayleigh surface waves
[The following animation was produced with a Mathematica notebook, Rayleigh.ma, which I created to investigate the behavior of Rayleigh waves which occur in solids. This Mathematica notebook contains several other graphs which further analyzer the behavior of Rayleigh waves.]
Another example of waves with both longitudinal and transverse motion may be found in solids as Rayleigh surface waves. The particles in a solid, through which a Rayleigh surface wave passes, move in elliptical paths, with the major axis of the ellipse perpendicular to the surface of the solid. As the depth into the solid increases the "width" of the elliptical path decreases. Rayleigh waves are different from water waves in one important way. In a water wave all particles travel in clockwise circles. However, in a Rayleigh surface wave, particles at the surface trace out a counter-clockwise ellipse, while particles at a depth of more than 1/5th of a wavelength trace out clockwise ellispes. The movie below shows a Rayleigh wave travelling from left to right along the surface of a solid. I have identified two particles in blue to illustrate the counterclockwise-clockwise motion as a function of depth.
cassandra
Mechanical Waves are waves which propagate through a material medium (solid, liquid, or gas) at a wave speed which depends on the elastic and inertial properties of that medium. There are two basic types of wave motion for mechanical waves: longitudinal waves and transverse waves. The animations below demonstrate both types of wave and illustrate the difference between the motion of the wave and the motion of the particles in the medium through which the wave is travelling.
[The following animations were created using a modifed version of the Mathematica® Notebook " Sound Waves" by Mats Bengtsson.]
Longitudinal Waves
In a longitudinal wave the particle displacement is parallel to the direction of wave propagation. The animation below shows a one-dimensional longitudinal plane wave propagating down a tube. The particles do not move down the tube with the wave; they simply oscillate back and forth about their individual equilibrium positions. Pick a single particle and watch its motion. The wave is seen as the motion of the compressed region (ie, it is a pressure wave), which moves from left to right.
To see a animations of spherical longitudinal waves check out:
* Sound Radiation from Simple Sources
* Radiation from Cylindrical Sources
Transverse Waves
In a transverse wave the particle displacement is perpendicular to the direction of wave propagation. The animation below shows a one-dimensional transverse plane wave propagating from left to right. The particles do not move along with the wave; they simply oscillate up and down about their individual equilibrium positions as the wave passes by. Pick a single particle and watch its motion.
Water Waves
Water waves are an example of waves that involve a combination of both longitudinal and transverse motions. As a wave travels through the waver, the particles travel in clockwise circles. The radius of the circles decreases as the depth into the water increases. The movie below shows a water wave travelling from left to right in a region where the depth of the water is greater than the wavelength of the waves. I have identified two particles in blue to show that each particle indeed travels in a clockwise circle as the wave passes.
Rayleigh surface waves
[The following animation was produced with a Mathematica notebook, Rayleigh.ma, which I created to investigate the behavior of Rayleigh waves which occur in solids. This Mathematica notebook contains several other graphs which further analyzer the behavior of Rayleigh waves.]
Another example of waves with both longitudinal and transverse motion may be found in solids as Rayleigh surface waves. The particles in a solid, through which a Rayleigh surface wave passes, move in elliptical paths, with the major axis of the ellipse perpendicular to the surface of the solid. As the depth into the solid increases the "width" of the elliptical path decreases. Rayleigh waves are different from water waves in one important way. In a water wave all particles travel in clockwise circles. However, in a Rayleigh surface wave, particles at the surface trace out a counter-clockwise ellipse, while particles at a depth of more than 1/5th of a wavelength trace out clockwise ellispes. The movie below shows a Rayleigh wave travelling from left to right along the surface of a solid. I have identified two particles in blue to illustrate the counterclockwise-clockwise motion as a function of depth.
cassandra
Date :
Time : 9:48 AM
Title :
Time : 9:48 AM
Title :
nur aidah 3n1
Date :
Time : 9:48 AM
Title :
Time : 9:48 AM
Title :
4. What are the characteristics of sound waves?
Sound waves are often characterized by four basic qualities, though many more are related:
Frequency, Amplitude, Wave shape and Phase*
Some sound waves are periodic, in that the change from equilibrium (average atmospheric pressure) to maximum compression to maximum rarefaction back to equilibrium is repetitive. The 'round trip' back to the starting point just described is called a cycle. Periodic motion is classically demonstrated by the up and down motion of a dropped weight (mass) attached to a spring or by observing the motion of a pendulum. The amount of time a single cycle takes is called a period.
It is possible to measure frequency in seconds per cycle or periods, but it is far more common for sound measurements to use cycles per second.
Periodic motion depends on two prime factors; 1) elasticity, in that medium being distorted return to its original state (equilibrium), and 2) a source of energy to initiate and sustain motion. In the case of sound waves, the atmospheric pressure will return to the ambient pressure without an energy source to disturb it, and any vibrating surface will constitute an energy or excitation source.
Simple harmonic motion, the motion described by mass/spring example above, is represented in sound as a sine wave, which traces the mathematical shape of it namesake. A sinusoidal wave (which also includes a cosine wave) is the only wave shape that produces a singles frequency, as we will see in the waveform chapter. With any minute deviations in the sine shape, additional frequencies will be generated.
Noise is characterized as being aperiodic or having a non-repetitive pattern. There are many different types of noise, depending primarily on the random distribution of frequencies. For example, some types of noise may sound brighter than others.
Some periodic waveforms can be complex enough to be perceived as noise if our ears cannot detect perceptible pitches. Many real-world sounds, such as the "chiffy" attack of a flute note contain some combination of periodic and aperiodic components.
*It could be argued that phase is not a characteristic of a single wave, but only as a comparison between two or more waves.
cassandra