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Year 8 Science Revision (Forces (Friction is a type of force, air…
Year 8 Science Revision
Healthy
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Circulatory System
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There are three types of blood vessel: Veins, arteries and capillaries. Veins transport deoxygenated blood except in the pulmonary vein in which oxygenated blood is transported from the lungs to the heart. Arteries transport oxygenated blood except for the pulmonary artery, in which deoxygenated blood in the right ventricle is transported to the lungs for re-oxygenation. Capillaries are extremely thin vessels which form a network which transport nutrients to cells and take out waste products.
Smoking
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Cigarettes contain carbon monoxide which can clog up your blood and impair respiration (not breathing, respiration is the processing of oxygen and nutrients to create energy) for years.
Asthma causes the tubes in the lungs, the bronchi and bronchioles, to be much tighter, and they can tense up during an asthma attack, making them tighter and much harder to inhale and exhale.
Aerobic exercise trains the lungs to work faster and allows their capacity to increase, assisting in breathing generally.
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Gas Exchange System
The gas exchange system consists of the lungs, trachea, mouth and nose. The diaphragm in the chest expands giving more room for the lungs to expand, which sucks in air through the mouth and/or nose. This air travels down the trachea in the neck and enters the bronchioles and the bronchi in which it travels down to the alveoli. These alveoli diffuse the air into blood cells. If exhaling carbon dioxide, the alveoli diffuse the carbon dioxide back into the bronchioles and transport it back up through the bronchi and trachea to be exhaled when the diaphragm and lungs become smaller.
Chemistry
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Chemical Tests
Hydrogen: A splint is lit and held above the opening of a tube with a mixture inside. The splint is then exposed quickly to the gas. If a distinctive squeaky pop is heard the gas is hydrogen. If not, but the gas still ignites, there is a different combustible gas.
Oxygen: A splint is lit and is let to burn for a few seconds, then blown out. While the ember on the end of the splint is still glowing, the splint should be exposed to the gas in a tube. Upon exposure it should flare and re-ignite. This will show it is oxygen.
Acids & Alkalis
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Combining an acid and an alkaki neutralises them. This means their corrosive properties cease and they become water and a salt.
Examples of acids: Citric acid (in lemon juice), Uric acid (in urine), Acetic acid (in vinegar)
Examples of alkalis: Bleach, seawater, soapy water, drain cleaner
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Forces
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Objects do not want to change their speed. So, if you placed a baseball that wasn't moving at all in a vacuum with no forces acting on it, it would not move. Similarly, if the baseball was moving at 1mph, it would stay moving at 1mph until it encountered a force which altered that.
When forces are balanced, an object's shape, speed and angles stay the same.
When forces are unbalanced, an object's shape, speed and angles change.
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Pressure is the force per unit area. Underwater, pressure increases as the water gets deeper. So at the surface of the water you would feel no pressure, but 20 metres down you would feel more pressure. This is due to the simple fact: Water is heavy when there's lots of it.
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Energy
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The law of energy conservtion is that energy cannot be created nor destroyed, and can only move and have its type altered.
Body Parts
Organs
The heart acts as a pump for blood. It propels blood through the circulatory system for nutrient supply around the body. The heart's cells must all know to beat at the right point.
The lungs act as a transport for air and carbon dioxide in and out of the body. They are able to expand when they fill up with air and space is made for this by the diaphragm, a muscle which expands to stretch the chest open. The lungs contract when exhaling, and this is the process in which carbon dioxide (CO2) is taken out of the body
The stomach is a large bag of muscle full of stomach acid, which dissolves food in the stomach into the acid. The acid is then transported through the small intestines and then the large intestines where enzymes digest all the nutrients in the dissolved food. The remaining substance is feces, which is disposed of via the anus which is at the end of the large intestines.
The brain is the central control centre for your entire body. The brain sends out energy in the form of neural signals which are able to perform many tasks, such as moving muscles. The brain can also receive signals, such as those that the *eyes send when they detect light. Additionally the brain is you. Every thought you process is done by the brain and the brain alone. However some thoughts and actions are subconscious, such as telling your heart to beat or (usually, but probably not now i've mentioned it) telling your eyes to blink or breathing.
Muscles
Antagonistic muscles are a pair of muscles which work together. Take for example the bicep and tricep. When the bicep contracts the tricep relaxes and vice versa. This makes movement of the body simpler.
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Bones
It is part of your cereal that helps you move, it has milk which makes you stronger, with the calcium contained in it. It also helps the enamel on your teeth because this assists in the efficiency of chewing food.
The skull contains two major parts: the cranium and the jaw. These are connected via joints so that the jaw is able to be moved. On the front of the jaw, your teeth are also found. The cranium contains the brain.
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