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Tuesday, June 30, 2015

Introduction

              Use of man-made synthetic polymeric meterials plays a huge effect on our everyday life. A large number of industries (e.g. packaging, textile, automobile, paper etc ) are based on synthetic polymers (poly = many ; mer = Parts ) such as polyethylene (PE), poly (vinyl chloride) (PVC), polyesters, nylon etc. and natural polymers such as rubber, cellulose, etc These natural polymers have been used for a long time, for example natural rubber was discovered in 1492 by columbus when he was in south america.
Synthetic polymers and their applications
              Synthetic polymers can be classified according to their response to heat. A thermoplastic polymer is one that can be softened by heating and then formed into desired shapes by applying pressure (moulding). In contrast, thermosetting polymers are permanently hard at elevated temperatures and pressures. They cannot be softened and remoulded. Polymers can be divided mainly into four types depending on their properties - plastics (e.g. PVC) , fibres (e.g. polyamides), elastomers (e.g rubber) and adhesives (e.g. resins). One of the most interesting uses of polymers  (e.g. biomedical polymers) has beer as replacements for diseased, worn out or missing parts of the human body such as leg , arm, lung, heart, liver, kidney, arteries, teeth , knee joints and hip joints. Synthetic polymers could pose a serious threat to environment unless we make them biodegradable. 

             All polymers are macromolecules with the same repeating unit but all macromolecules are not polymers. For example, proteins and nucleic acids (DNA and RNA) are macromolecules but they do not have the same repeating unit. Natural polymers and macromolecules such as polysaccharides (e.g. Cellulose, starch, etc) and nucleic acids (responsible for heredity) based on sugars and phosphates are discussed in session.

            When naming homopolymers (i.e polymers with one monomer unit), the name of the monomer is written after the prefix poly, e.g polyethylene. If the name of the monomer is not a one word the name of the monomer is written within brackets, e.g. poly (vinyl chloride). 

Synthetic polymers and their applications

Synthetic polymers and their applications

Introduction

              Use of man-made synthetic polymeric meterials plays a huge effect on our everyday life. A large number of industries (e.g. packaging, textile, automobile, paper etc ) are based on synthetic polymers (poly = many ; mer = Parts ) such as polyethylene (PE), poly (vinyl chloride) (PVC), polyesters, nylon etc. and natural polymers such as rubber, cellulose, etc These natural polymers have been used for a long time, for example natural rubber was discovered in 1492 by columbus when he was in south america.
Synthetic polymers and their applications
              Synthetic polymers can be classified according to their response to heat. A thermoplastic polymer is one that can be softened by heating and then formed into desired shapes by applying pressure (moulding). In contrast, thermosetting polymers are permanently hard at elevated temperatures and pressures. They cannot be softened and remoulded. Polymers can be divided mainly into four types depending on their properties - plastics (e.g. PVC) , fibres (e.g. polyamides), elastomers (e.g rubber) and adhesives (e.g. resins). One of the most interesting uses of polymers  (e.g. biomedical polymers) has beer as replacements for diseased, worn out or missing parts of the human body such as leg , arm, lung, heart, liver, kidney, arteries, teeth , knee joints and hip joints. Synthetic polymers could pose a serious threat to environment unless we make them biodegradable. 

             All polymers are macromolecules with the same repeating unit but all macromolecules are not polymers. For example, proteins and nucleic acids (DNA and RNA) are macromolecules but they do not have the same repeating unit. Natural polymers and macromolecules such as polysaccharides (e.g. Cellulose, starch, etc) and nucleic acids (responsible for heredity) based on sugars and phosphates are discussed in session.

            When naming homopolymers (i.e polymers with one monomer unit), the name of the monomer is written after the prefix poly, e.g polyethylene. If the name of the monomer is not a one word the name of the monomer is written within brackets, e.g. poly (vinyl chloride). 

Synthetic polymers and their applications

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Posted at 11:25 PM |  by Unknown

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Sunday, June 28, 2015

During the process of transmission, it is obvious that something passes from the sounding body to the ear, in order to produce the sensation of sound from the motion of the sounding body we guess that some sort of wave motion passes outwards from it. It can be easily shown that a medium (air or some other medium) is indispensable for the propagation of sound.
The Transmission of sounds

All materials, however, can transmit sound waves, if a faint tapping or scratching be made at one end of a long table, on putting the ear to the other end of the table, this sound can be heard even when the sound is too faint to be heard if the ear is not placed close to the wood. This shows that sound waves have been transmitted through the wood.

If you examine it carefully, you will notice that every source of sound or part of it vibrates when it is set to produce sound. We hope you are familiar with the prongs of a tuning-fork. The prongs of a sounding tuning-fork and the plucked string of a guitar can actually be seen to vibrate. The vibration of a drum or a bell may not be visible but they can often be felt: when they are checked by the hand the sound ceases.

Question

What is vibration ?

A vibration is a rapid to and fro motion which is continually repeated.

The vibration of a prong of a tuning-fork may be investigated by attaching a bristle to one of its prongs, and drawing under it a smoke glass plate while the prongs are vibrating. (Image 1.1.1)

A vibration is a rapid to and fro motion which is continually repeated.
(Image 1.1.1)

If a glass plate is moved with a uniform velocity the trace made by the  bristle will be similar to the wave pattern shown in Image 1.1.2

(Image 1.1.2)


This particular type of vibration is the simplest possible, and is called simple harmonic motion as you know from earlier sessions.

Due to this vibration of the source of sound, the surrounding medium gets disturbed and this disturbance travel through the medium without the medium moving bodily with it . We call this is a wave. a wave allows energy to be transferred from one point to another some distance away without any particles of the medium travelling between the two points. 

There are many kinds of waves such as light waves, radio waves, water waves and wave in stretching strings, rods and so on. All these waves can be divided into two main categories. 
  1. Transverse waves
  2.  Longitudinal waves

The Transmission of sounds

During the process of transmission, it is obvious that something passes from the sounding body to the ear, in order to produce the sensation of sound from the motion of the sounding body we guess that some sort of wave motion passes outwards from it. It can be easily shown that a medium (air or some other medium) is indispensable for the propagation of sound.
The Transmission of sounds

All materials, however, can transmit sound waves, if a faint tapping or scratching be made at one end of a long table, on putting the ear to the other end of the table, this sound can be heard even when the sound is too faint to be heard if the ear is not placed close to the wood. This shows that sound waves have been transmitted through the wood.

If you examine it carefully, you will notice that every source of sound or part of it vibrates when it is set to produce sound. We hope you are familiar with the prongs of a tuning-fork. The prongs of a sounding tuning-fork and the plucked string of a guitar can actually be seen to vibrate. The vibration of a drum or a bell may not be visible but they can often be felt: when they are checked by the hand the sound ceases.

Question

What is vibration ?

A vibration is a rapid to and fro motion which is continually repeated.

The vibration of a prong of a tuning-fork may be investigated by attaching a bristle to one of its prongs, and drawing under it a smoke glass plate while the prongs are vibrating. (Image 1.1.1)

A vibration is a rapid to and fro motion which is continually repeated.
(Image 1.1.1)

If a glass plate is moved with a uniform velocity the trace made by the  bristle will be similar to the wave pattern shown in Image 1.1.2

(Image 1.1.2)


This particular type of vibration is the simplest possible, and is called simple harmonic motion as you know from earlier sessions.

Due to this vibration of the source of sound, the surrounding medium gets disturbed and this disturbance travel through the medium without the medium moving bodily with it . We call this is a wave. a wave allows energy to be transferred from one point to another some distance away without any particles of the medium travelling between the two points. 

There are many kinds of waves such as light waves, radio waves, water waves and wave in stretching strings, rods and so on. All these waves can be divided into two main categories. 
  1. Transverse waves
  2.  Longitudinal waves

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Posted at 9:04 PM |  by Unknown

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Wednesday, June 17, 2015

Gases are all around us. Many of them are vital to our life. The oxygen we breathe reacts with certain nutrients such as carbohydrates or lipids to give us energy. We exhale carbon dioxide and water. Plants take up carbon dioxide and water vapor to convert back in to oxygen and nutrients in the presence of sun light.
Gases are all around us. Many of them are vital to our life.

Other gases in the atmosphere have different roles. For an example, plants cannot use atmospheric nitrogen directly. Certain micro organisms called nitrogen fixing bacteria take up nitrogen and convert it to nitrates.

Some of the gases are responsible for the green house effect. These gases include; water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), chlorofluorocarbons (CFxClx) and tropospheric ozone (O3).

Characteristic properties of gases

There are some general Characteristic of gases which distinguish them from solids and gases. These are called Characteristic properties of gases. Some of them are listed as follows.

1. They are easy to compress - compressibility.

In General, compressibility is the ability of something to be "squashed" into a smaller space. Gases are easy to compress even with relatively little pressure. An internal combustion engine is a good example. Compared to gases, liquids are very less compressible. How about solids ? You can understand the compressibility of solids, if you try to squeeze a big table in to very small room. It is really hard!

2. They expand to fill their containers- expandability.

We know that gases tend expand until they fill whatever contains them. Therefore, it is safe to assume that the volume of gas is equal to the volume of its container.

3. They occupy far more space than the liquids or solids at the same pressure from which they form.

Generally, the volume of a liquid or solid increases approximately 800 times when it forms  a gas. This large change in volume can be utilized to do work such as steam engine. Here, the escaping steam can be made to do work. Same phenomenon occurs on a much smaller scale when we "POP" popcorn. When the kernel of popcorn is heated in oil, the liquid inside the kernel turns in to gases. The pressure build up inside the kernel is enormous and the kernel eventually explodes.

Common gases at room temperature

It might be useful to understand which elements or compounds are gases at room temperature. 

According to this table, we can observe several patterns.

1. Both elements (eg: He) and compounds (eg: CO2) may be gases room temperature.
2. Elements that are gases at room temperature are all non metals (eg: He, O2).
3. Compounds that are gases at room temperature are all covalent compounds (eg: CO2,NH3)
4. All these gases have relatively small molecular weights but there may be rare exceptions.

Some of the common gases at room temperature.

Element or compound
Molecular Weight
H2 (hydrogen)
2.02
He (helium)
4.00
CH4 (methane)
16.02
NH2 (ammonia)
17.03
Ne (neon)
20.18
HCN (hydrogen cyanide)
27.03
CO (carbon monoxide)
28.01
N2 (nitrogen)
28.01
NO (nitrogen oxide)
30.01
C2H6 (ethane)
30.07
O2 (oxygen)
32.00
PH3 (phosphine)
34.00
H2S (hydrogen sulfide)
34.08
HCl (hydrogen chloride)
36.46
F2 (fluorine )
38.00
Ar (argon)
39.95
CO2 (carbon dioxide)
44.01
N2O ( dinitrogen oxide)
44.01
C3H8  ( propane)
44.10
NO2 (nitrogen dioxide)
46.01
O3 (ozone)
48.00

Why gases are important ?

Gases are all around us. Many of them are vital to our life. The oxygen we breathe reacts with certain nutrients such as carbohydrates or lipids to give us energy. We exhale carbon dioxide and water. Plants take up carbon dioxide and water vapor to convert back in to oxygen and nutrients in the presence of sun light.
Gases are all around us. Many of them are vital to our life.

Other gases in the atmosphere have different roles. For an example, plants cannot use atmospheric nitrogen directly. Certain micro organisms called nitrogen fixing bacteria take up nitrogen and convert it to nitrates.

Some of the gases are responsible for the green house effect. These gases include; water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), chlorofluorocarbons (CFxClx) and tropospheric ozone (O3).

Characteristic properties of gases

There are some general Characteristic of gases which distinguish them from solids and gases. These are called Characteristic properties of gases. Some of them are listed as follows.

1. They are easy to compress - compressibility.

In General, compressibility is the ability of something to be "squashed" into a smaller space. Gases are easy to compress even with relatively little pressure. An internal combustion engine is a good example. Compared to gases, liquids are very less compressible. How about solids ? You can understand the compressibility of solids, if you try to squeeze a big table in to very small room. It is really hard!

2. They expand to fill their containers- expandability.

We know that gases tend expand until they fill whatever contains them. Therefore, it is safe to assume that the volume of gas is equal to the volume of its container.

3. They occupy far more space than the liquids or solids at the same pressure from which they form.

Generally, the volume of a liquid or solid increases approximately 800 times when it forms  a gas. This large change in volume can be utilized to do work such as steam engine. Here, the escaping steam can be made to do work. Same phenomenon occurs on a much smaller scale when we "POP" popcorn. When the kernel of popcorn is heated in oil, the liquid inside the kernel turns in to gases. The pressure build up inside the kernel is enormous and the kernel eventually explodes.

Common gases at room temperature

It might be useful to understand which elements or compounds are gases at room temperature. 

According to this table, we can observe several patterns.

1. Both elements (eg: He) and compounds (eg: CO2) may be gases room temperature.
2. Elements that are gases at room temperature are all non metals (eg: He, O2).
3. Compounds that are gases at room temperature are all covalent compounds (eg: CO2,NH3)
4. All these gases have relatively small molecular weights but there may be rare exceptions.

Some of the common gases at room temperature.

Element or compound
Molecular Weight
H2 (hydrogen)
2.02
He (helium)
4.00
CH4 (methane)
16.02
NH2 (ammonia)
17.03
Ne (neon)
20.18
HCN (hydrogen cyanide)
27.03
CO (carbon monoxide)
28.01
N2 (nitrogen)
28.01
NO (nitrogen oxide)
30.01
C2H6 (ethane)
30.07
O2 (oxygen)
32.00
PH3 (phosphine)
34.00
H2S (hydrogen sulfide)
34.08
HCl (hydrogen chloride)
36.46
F2 (fluorine )
38.00
Ar (argon)
39.95
CO2 (carbon dioxide)
44.01
N2O ( dinitrogen oxide)
44.01
C3H8  ( propane)
44.10
NO2 (nitrogen dioxide)
46.01
O3 (ozone)
48.00

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Posted at 12:08 AM |  by Unknown

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Tuesday, June 16, 2015

Matter is defined as anything that has mass and takes space. It is everything around us. Rocks, oceans, plants, animals, houses and cars are all examples of matter. Although matter appears to be continuous and unbroken, it is not so. According to the ancient Greek Philosopher Democritus (470- 370 BC) matter is actually composed of discrete tiny particles called atoms, derived from the Greek word atoms, meaning "indivisible" (Image 1) . Atoms may not be visible to the macroscopic eye, however, modern instrumental techniques available today such as X-ray diffraction and scanning tunneling microscopy show the position of individual atoms (Image 2).

A penny is made up of copper atoms packed tightly together
(Image 1) A penny is made up of copper atoms packed tightly together.

Individual atoms can be seen as bumps on the surface of a solid by scanning tunneling microscopy. This is an image of the surface of copper.

(Image 2) Individual atoms can be seen as bumps on the surface of a solid by scanning tunneling microscopy. This is an image of the surface of copper.

You may remember from your ordinary level work that a purple solution is formed when a crystal of potassium permanganate (KMnO4) is placed in a beaker of water. This observation can be explained by the particulate nature of matter. Both the crystal and water are made up of particles. These particles mix together and as a result a coloured solution is produced. The movement of different particles among each other is called diffusion. (Image 3)  will further illustrate this phenomenon.

Mixing of potassium permanganate particles with water particles to give a coloured solution.


(Image 3) Mixing of potassium permanganate particles with water particles to give a coloured solution.

The Particulate nature of matter

Matter is defined as anything that has mass and takes space. It is everything around us. Rocks, oceans, plants, animals, houses and cars are all examples of matter. Although matter appears to be continuous and unbroken, it is not so. According to the ancient Greek Philosopher Democritus (470- 370 BC) matter is actually composed of discrete tiny particles called atoms, derived from the Greek word atoms, meaning "indivisible" (Image 1) . Atoms may not be visible to the macroscopic eye, however, modern instrumental techniques available today such as X-ray diffraction and scanning tunneling microscopy show the position of individual atoms (Image 2).

A penny is made up of copper atoms packed tightly together
(Image 1) A penny is made up of copper atoms packed tightly together.

Individual atoms can be seen as bumps on the surface of a solid by scanning tunneling microscopy. This is an image of the surface of copper.

(Image 2) Individual atoms can be seen as bumps on the surface of a solid by scanning tunneling microscopy. This is an image of the surface of copper.

You may remember from your ordinary level work that a purple solution is formed when a crystal of potassium permanganate (KMnO4) is placed in a beaker of water. This observation can be explained by the particulate nature of matter. Both the crystal and water are made up of particles. These particles mix together and as a result a coloured solution is produced. The movement of different particles among each other is called diffusion. (Image 3)  will further illustrate this phenomenon.

Mixing of potassium permanganate particles with water particles to give a coloured solution.


(Image 3) Mixing of potassium permanganate particles with water particles to give a coloured solution.

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Posted at 2:44 AM |  by Unknown

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Monday, June 15, 2015

Do you know ice is a solid and water is a liquid; how the battery in your car works to start the engine; why glass is fragile but not plastics; how different colors originate in fireworks display; why fertilizers are used in agriculture; how bodies use food to maintain life ? Answers to all these questions and many more supplied by chemistry.

Chemistry is the science that deals with the study of matter and the Changes it undergoes

Chemistry is the science that deals with the study of matter and the Changes it undergoes. Often, it is referred to as the central science because it is needed to understand the other sciences and technologies.

Chemistry has enriched our lives in many ways. It has improved healthcare through the development of new drugs and vaccines that enhance our health and prolong our lives. The food production has been increased by the development of fertilizers and pesticides, which are all chemicals. The food we eat is colored, flavored, and preserved by various chemical additives. Our domestic requirements, e.g. Soap, Shampoo, Toothpaste, Cosmetics,......etc. are provided by chemistry. Amenities such as air conditioning, refrigeration and electronic gadgets that we use in our day to day life for our comfort, convenience and pleasure are also provided by chemistry. Products that we need for construction ( Cement glass, ceramics, Plastics, Paints, .... etc) are produced through the exploitation on chemistry. Fuels used by vehicles and machinery also depend on chemistry for their manufacture and purification.

As you can see, the uses of chemistry are many. However, its misuse can have disastrous consequences on living beings and the environment. Therefore, a basic knowledge of chemistry will help you understand the world around you better.

Why Study Chemistry ?

Do you know ice is a solid and water is a liquid; how the battery in your car works to start the engine; why glass is fragile but not plastics; how different colors originate in fireworks display; why fertilizers are used in agriculture; how bodies use food to maintain life ? Answers to all these questions and many more supplied by chemistry.

Chemistry is the science that deals with the study of matter and the Changes it undergoes

Chemistry is the science that deals with the study of matter and the Changes it undergoes. Often, it is referred to as the central science because it is needed to understand the other sciences and technologies.

Chemistry has enriched our lives in many ways. It has improved healthcare through the development of new drugs and vaccines that enhance our health and prolong our lives. The food production has been increased by the development of fertilizers and pesticides, which are all chemicals. The food we eat is colored, flavored, and preserved by various chemical additives. Our domestic requirements, e.g. Soap, Shampoo, Toothpaste, Cosmetics,......etc. are provided by chemistry. Amenities such as air conditioning, refrigeration and electronic gadgets that we use in our day to day life for our comfort, convenience and pleasure are also provided by chemistry. Products that we need for construction ( Cement glass, ceramics, Plastics, Paints, .... etc) are produced through the exploitation on chemistry. Fuels used by vehicles and machinery also depend on chemistry for their manufacture and purification.

As you can see, the uses of chemistry are many. However, its misuse can have disastrous consequences on living beings and the environment. Therefore, a basic knowledge of chemistry will help you understand the world around you better.

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Posted at 12:07 AM |  by Unknown

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