These two processes have been taught since Primary 3. However, some students in Secondary 1 can't even tell the the difference between the two.
Breathing:
This process is much easier than respiration. Breathing is the process in which living ,things take in air, and exhale air. Evaporation involves the he mouth, the nose and nostrils, the pharynx, the larynx, the trachea, the bronchi and bronchioles, the lungs, the diaphragm, and the terminal branches of the respiratory tree, such as the alveoli. To take in air, our diaphragm moves down, creating a vacuum to suck up air from the surroundings.
Respiration:
This process involves all the cells in our body, not just in the respiratory system. during respiration. There are two types of respiration, anaerobic and aerobic respiration.
Anaerobic respiration is more complicated than aerobic respiration. It breaks down oxygen and glucose into carbon dioxide and energy.
Aerobic respiration breaks down glucose into energy.
Friday, September 3, 2010
Thursday, September 2, 2010
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Therefore, the smaller the area, the less the pressure.
For example:
The cuboids are identical however, the cuboid on the left exerts less pressure than the one on the right. This is because the cuboid on the left has less area applied perpendicular towards the fore, weight.
For example:
The cuboids are identical however, the cuboid on the left exerts less pressure than the one on the right. This is because the cuboid on the left has less area applied perpendicular towards the fore, weight.
Seperation techniques
There are many ways to seperate a substance from its solution.
To seperate a solvent from a solution, we can use distillation(e.g: pure water from seawater)
To seperate a solute from a solution, we can use crystallisation(e.g: to purify, as the name implies, crystals) or evaporation to dryness(e.g: salt crystals from seawater)
To seperate a liquid from a solution of two liquids with significantly different boiling points, we can use fractional distillation(e.g: to seperate ethanol from a solution of ethanol and water)
To seperate an immiscible liquid from a mixture, we can use filtration(e.g: to seperate sand from a mixture of sand and water)
To seperate an immiscible liquid from another immiscible liquid with different densities, we can use seperation funnel(e.g: to seperate water from a mixture of water and oil)
To seperate a solvent from a solution, we can use distillation(e.g: pure water from seawater)
To seperate a solute from a solution, we can use crystallisation(e.g: to purify, as the name implies, crystals) or evaporation to dryness(e.g: salt crystals from seawater)
To seperate a liquid from a solution of two liquids with significantly different boiling points, we can use fractional distillation(e.g: to seperate ethanol from a solution of ethanol and water)
To seperate an immiscible liquid from a mixture, we can use filtration(e.g: to seperate sand from a mixture of sand and water)
To seperate an immiscible liquid from another immiscible liquid with different densities, we can use seperation funnel(e.g: to seperate water from a mixture of water and oil)
Carbon and its Allotropes
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic. It is special as it has many allotrope.
Allotropy or allotropism is a behavior shown by some chemical elements: these elements can exist in two or more different forms, known as allotropes of that element. In each allotrope, the element's atoms are bonded together in a different manner, resulting in a different form.
Probably the most common allotrope of carbon is the diamond. Diamonds are formed under tremendous heat and pressure. These conditions exist 150 km to 200 km beneath the earth's surface, where the temperatures are extremely high ranging from 900ºC to 1300ºC.The diamond is the hardest known natural mineral in the world. Therefore, no known substance can even scratch a diamond. Diamonds are usually used for industrial puposes ,as it is hard and can sustain high temperatures, and as jewelry. The chemical bond of a diamond form an inflexible three dimensional lattice(a structure made from strips which cross over each other with spaces between). This structure makes it weaker than the other allotropes of carbon.
Graphite, also a common allotrope of carbon, is used in our everyday life as pencil lead. The atoms in graphite are tightly bonded into sheets, which can slide easily over one another. Graphite is also a conductor of electricity, therefore it can be used in batteries and in electric motors. The picture below shows how the atoms are arranged.
Another form of carbon is Buckminster fullerine. It is a recently discovered allotrope of carbon. It is nicknamed “bucky ball” due to its spherical atomic structure. In recent years, fullerene compounds have been found to act as superconductors, substances capable of conducting electricity without resistance at very low temperatures. This could also be a cure for AIDS. Research has found that this bucky ball can interfere with the reproductive system of HIV.
Allotropy or allotropism is a behavior shown by some chemical elements: these elements can exist in two or more different forms, known as allotropes of that element. In each allotrope, the element's atoms are bonded together in a different manner, resulting in a different form.
Probably the most common allotrope of carbon is the diamond. Diamonds are formed under tremendous heat and pressure. These conditions exist 150 km to 200 km beneath the earth's surface, where the temperatures are extremely high ranging from 900ºC to 1300ºC.The diamond is the hardest known natural mineral in the world. Therefore, no known substance can even scratch a diamond. Diamonds are usually used for industrial puposes ,as it is hard and can sustain high temperatures, and as jewelry. The chemical bond of a diamond form an inflexible three dimensional lattice(a structure made from strips which cross over each other with spaces between). This structure makes it weaker than the other allotropes of carbon.
Graphite, also a common allotrope of carbon, is used in our everyday life as pencil lead. The atoms in graphite are tightly bonded into sheets, which can slide easily over one another. Graphite is also a conductor of electricity, therefore it can be used in batteries and in electric motors. The picture below shows how the atoms are arranged.
Another form of carbon is Buckminster fullerine. It is a recently discovered allotrope of carbon. It is nicknamed “bucky ball” due to its spherical atomic structure. In recent years, fullerene compounds have been found to act as superconductors, substances capable of conducting electricity without resistance at very low temperatures. This could also be a cure for AIDS. Research has found that this bucky ball can interfere with the reproductive system of HIV.
Why ice floats on water?
Have you wondered why ice floats on water? This is because ice is lighter than water, thus giving it a lesser density.
The reason why ice is lighter than water is that a certain mass of ice occupies more space than the same mass of water.
A water molecule is composed of two hydrogen atoms (H) and one oxygen atom (O). The atoms of hydrogen and oxygen are bound by sharing their electrons with one another. This bond is called a “covalent bond”.However, since oxygen atoms pull electrons more strongly than hydrogen atoms, the oxygen atom in a water molecule has a slightly negative charge and the hydrogen atoms have a slightly positive charge. So adjacent water molecules are attracted to one another through the slightly negatively charged oxygen atoms and the slightly positively charged hydrogen atoms. This interaction is called “hydrogen bonding”.
Structure of ice and water:
Ice has a diamond structure due to the hydrogen bonding. Water does not have such an orderly structure, but water molecules are squeezed close to one another.
The one with more space is ice and the one with less space is ice.
As you can see, ice has more space in ice than in water! This is the reason why ice is lighter than water. Therefore, ice can float on water.
The reason why ice is lighter than water is that a certain mass of ice occupies more space than the same mass of water.
A water molecule is composed of two hydrogen atoms (H) and one oxygen atom (O). The atoms of hydrogen and oxygen are bound by sharing their electrons with one another. This bond is called a “covalent bond”.However, since oxygen atoms pull electrons more strongly than hydrogen atoms, the oxygen atom in a water molecule has a slightly negative charge and the hydrogen atoms have a slightly positive charge. So adjacent water molecules are attracted to one another through the slightly negatively charged oxygen atoms and the slightly positively charged hydrogen atoms. This interaction is called “hydrogen bonding”.
Structure of ice and water:
Ice has a diamond structure due to the hydrogen bonding. Water does not have such an orderly structure, but water molecules are squeezed close to one another.
The one with more space is ice and the one with less space is ice.
As you can see, ice has more space in ice than in water! This is the reason why ice is lighter than water. Therefore, ice can float on water.
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