Science and Related Subjects

The Respiratory System
We rarely think about breathing unless we’re out of breath. The act of breathing is part of the respiratory system, a complex process where air travels into and out of the lungs.

Respiration is slightly different, where exercise causes muscles to release energy in the form of glucose. Both systems are co-dependent, especially when you’re playing sport and inhaling greater quantities of oxygen.



Human Respiratory System:
The human respiratory system is made up of air passages, lungs and the respiratory muscles.

Nose: most breathing and gas exchange occur through the nose. It is lined by a layer of mucus and hair to trap the dust and germs in the air. It is also supplied with a dense network of blood capillaries to warm the air entering the body.

Pharynx: Works together with the epiglottis to block the nasal cavity and the trachea during swallowing food, to prevent it from entering the respiratory system.

Trachea (windpipe): this is a tube that connects the nasal cavity and larynx to the lungs. It is lined with a layer of ciliated epithelium cells and goblet cells which secrete mucus that traps bacteria and dust from inhaled air and gets moved upwards to the larynx by the cilia.

It is then either spit out or swallowed to the stomach where it is eliminated by acid.
Bronchi: when the trachea reaches the lungs, it is divided into two tubes, one goes to the right lung and one goes to the left lung. These are called the bronchi. The bronchi are then divided bronchioles that extended deeper into the lungs.

Alveoli (air sacs): these are tiny bags full of gas; they are present in the lungs in large amounts (several million alveolus in each lung). They give the lungs a much larger surface area (about 70 m2) for faster diffusion of gases between them and the blood.

Rib Cage: the lungs are protected by this cage of bones. It surrounds all the thoracic cavity. They are 12 pairs of ribs; one pair extends from one of the first 12 vertebrae of the vertebral column. All of the ribs except for the last two pairs are connected to the sternum, the chest bone. Each pair of ribs is connected to the pairs above it and below it by muscle fibres called inter costal muscles. The rib cage and the lungs are separated by an elastic layer called pleural membrane, or pleura for short. It protects the lungs from damage caused by friction with the rib cage during breathing.

Diaphragm: this is a sheath of muscles that separates the thoracic cavity from the abdominal cavity. Together with the ribs and the inter costal muscles, it plays a big role in breathing and gas exchange.


Gas Exchange (Breathing):
Breathing is different from respiration. Breathing is just the exchange of waste gases from the body with fresh air from the atmosphere. The action of breathing fresh air in is called inhaling; the action of breathing waste gases out is called exhaling.

During Inhaling, the brain sends electric impulses by nerves to the diaphragm and the inter costal muscles. The diaphragm contracts becoming flatter. The inter costal muscles also contract and move the ribs in an outer upwards directions. These actions expand the thoracic cavity making the lungs expand, thus increasing the increasing the volume, with the volume increasing the internal pressure decreases which makes air enter the lungs through the mouth, nose and trachea.

During Exhaling, the diaphragm and the inter costal muscles relax again, contracting the thoracic cavity thus squeezing the air out of the lungs to the trachea and mouth and nose to the atmosphere.



Respiratory System in Action:
Inhaling occurs, air is absorbed by lungs, it enters the nose where bacteria and dust in it are trapped by mucus and warmed by blood capillaries. The air enters the trachea where it is cleaned again by cilia.
The bronchi take the air from the trachea to each lung.
Bronchi divide into several bronchioles; each one has a group of alveoli at the end of it.
In the alveoli gas exchange takes place where the oxygen rich air diffuses into the blood capillaries of the pulmonary arteries and the carbon dioxide rich gas diffuses into the alveoli to be exhaled.

The pulmonary vein carries the oxygenated fresh air to the heart where it is pumped to all the body cells.
The inter costal muscles and diaphragm relax squeezing the waste gases out of the lungs, this is exhalation.

Gas Exchange in Alveoli:
Each alveolus is supplied with blood capillaries. These come from the pulmonary artery and they contain deoxygenated blood rich in carbon dioxide. The concentration of oxygen is very high inside the alveolus and very low in the blood, so oxygen molecules diffuse from the alveolus to the red blood cells and combine with haemoglobin. At the very same time this occurs, carbon dioxide diffuses from the blood to the alveolus because the concentration of it is very high in the blood and low in the alveolus.


Adaptations of Alveoli:
Gas exchange happens because of several factors in the alveolus and the blood capillaries that control the rate of gas exchange:

Very thin wall of both the alveolus and the capillary, they are one cell thick which makes the diffusion distance shorter, increasing the rate.
The difference in concentration of gases between the alveolus and the capillary is very large, increasing the diffusion rate of gases.
The alveolus are balloon shaped which gives it a very large surface area for faster diffusion.
The walls of the alveolus are lined by a thin film of water in which gases dissolve in during diffusion, this makes it faster.

Composition of Inspired and Expired Air:
Gas

Inspired Air

Expired Air

Oxygen

21%

16%

Carbon Dioxide

0.04%

4%

Nitrogen

79%

79%

Water Vapour

Variable

High


Lung Capacity:
When lungs of an adult are fully inflated they have a volume of about 5 litres.

Tidal Volume: This is the volume of air breathed in and out at rest, this is 0.5 litres.

Vital Volume: The maximum volume of air that can be breathed in and out, at exercise for example is 3 litres.

Residual Volume: The lungs have to have a certain volume of air inside them all the time to keep shape. This is the residual volume and it is 1.5 litres. This air is renewed through breathing.

Aerobic Respiration:
A chemical, metabolic reaction that burns down glucose with oxygen producing carbon dioxide, water vapour and lots of energy

Aerobic Respiration: the release of relatively large amounts of energy in cells by the breakdown of food substances in the presence of oxygen.

Anaerobic Respiration:
Some organisms are able to respire and release energy when oxygen is lacking. This is anaerobic respiration. These are like yeast, bacteria and other organisms. Humans can also respire anaerobically for a short period of time. The amount of energy produce is much smaller than that produced during aerobic respiration though.

Anaerobic respiration: the release of relatively small amount of energy by the breakdown of food substances in the absence of oxygen.

C6H12O6 (aq) + 6O2 (g) → 6 O2 (g) + 6H2O (l)

Anaerobic Respiration I Yeast: Yeast is able to respire anaerobically by breaking down glucose molecules into ethanol and carbon dioxide.

C6H12O6 → 2C2H5OH + 6CO2

Ethanol is produced here, so it is a fermentation reaction. Do remember that glucose is the only reactant.

Anaerobic Respiration in Humans:
When the amount of oxygen received by the muscle cells of the body is not enough to carry out all respiration aerobically, the cells respire anaerobically. But they cannot go like that for a long time. The anaerobic respiration in humans is different than of yeast. Lactic acid is produced instead of ethanol, and no carbon dioxide is produced.

C6H12O6 → 2C3H6O3

The lactic acid produced is very toxic and harmful to the body. That is why it has to be broken down with oxygen as soon as possible. This is called oxygen debt. Breaking down lactic acid releases energy too, if you add up the amount of energy produced during breaking down lactic acid and anaerobic respiration, you will find that it is the same as the amount produced during aerobic respiration.


Effects of Smoking:
Short Term Effects:
Cilia can’t vibrate anymore, the air inhaled isn’t clean. Goblet cells release more mucus which makes the trachea narrower.
Ni****ne increases heart beat rate and blood pressure.
Carbon monoxide combines with haemoglobin instead of oxygen combining with it.
Carboxyhaemoglobin is formed which is stable.
Less oxygen transported to cells.
Diseases Caused By Tar:
Chronic Bronchitis:
Tar makes goblet cells in trachea produce excess mucus
Mucus falls into lungs
Bacteria in mucus breed causing infections like bronchitis
The layer of excess mucus lining the walls of the alveoli increase the diffusion distance of gases making gas exchange slower
Emphysema:
The excess mucus lining the alveoli irritates it, causing strong coughs which damage the alveoli.
The alveoli lose its shape and surface area making gas exchange much slower.
This cause short breathes and sounds while breathing.
Lung Cancer:
When tar reaches the lungs, it is absorbed by cells of the bronchi, bronchioles and the lungs.
The tar causes excessive division and reproduction of these cells which develops into cancer
The cancer can be spread to other organs too.
Diseases Caused By Ni****ne:
Coronary Heart Disease:
Ni****ne helps cholesterol deposition on walls of coronary arteries. This causes atheroma.
Carbon monoxide also increases risk of blood clots forming which might results in blocking the artery.
Less oxygen is delivered to heart cells, a heart attack or failure can take place leading to death.

Biology:
Transport In Humans

The human transport system is a system of tubes with a pump and valves to ensure one way blood flow. We need a transport system to deliver oxygen, nutrients and other substances to all our body cells, and take away waste products from them.

The oxygenated blood (high in oxygen, red in color) comes to the heart from the lungs in the pulmonary vein; the heart pumps it to the aorta (an artery) to the rest of the body. The deoxygenated blood returns to the heart from the body in the vena cava (a vein), the heart pumps is to the lungs to get rid of the carbon dioxide.

Oxygenated Blood: Red color, high oxygen low Carbon dioxide.
Deoxygenated Blood: Blue color, low oxygen high Carbon dioxide.
Did you notice that during one circulation, the blood went through the heart twice, this is why we call it double circulation.

When the blood is flowing away from the heart, it has a very high pressure, when it is flowing towards the heart it has a lower pressure.

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Acceleration Formula
Acceleration is a measure of how quickly the velocity of an object changes. So, the acceleration is the change in the velocity, divided by the time. Acceleration has a magnitude (a value) and a direction. The direction of the acceleration does not have to be the same as the direction of the velocity. The units for acceleration are meters per second squared (m/s2).

a = acceleration (m/s2)

vf = the final velocity (m/s)

vi = the initial velocity (m/s)

t = the time in which the change occurs (s)

Δv = short form for "the change in" velocity (m/s)

Acceleration Formula Questions:

A child drops a rock off of a cliff. The rock falls for 15.0 s before hitting the ground. The acceleration due to gravity is g = 9.80 m/s2. What was the velocity of the rock the instant before it hit the ground?

Answer: The rock was released from rest, so the initial velocity is vi = 0.00 m/s. The time in which the change occurred is 15.0 s. The acceleration is 9.80 m/s2. The final velocity must be found, so rearrange the equation:

vf = vi + at

vf = 0.00 m/s +(9.80 m/s2)(15.0 s)

vf = 147 m/s

The rock is falling, so the direction of the velocity is down.

Understanding rate of Reaction


Rate of reaction is defined as the change in the amount of reactants or products per unit time.
It is a measure of how fast a reaction occurs.
Fast Reaction = Rate of reaction is high.
Slow Reaction = Rate of reaction is low
A fast reaction taken shorter time for the reaction to complete.

Example of fast reaction
Type of Reaction Example
Combustion Combustion of magnesium in oxygen
Mg+O2→MgO
Combustion of ethane (C2H6)
C2H6+72O2→2CO2+3H2O
Reaction between reactive metal and water Reaction between potassium and water
2K+2H2O→2KOH+H2
Reaction between metal carbonate and acid Reaction between limestone/ marble and sulphuric acid
CaCO3+H2SO4→CaSO4+CO2+H2O
Ionic precipitation (Double decomposition) Precipitation of silver(I) chloride
AgNO3+ HCl→AgCl + HNO3

Example of slow reaction
Type of Reaction Example
Photosynthesis
6CO2+ 6 H2O→C6H12O6+ 6O2
Rusting
4Fe+3O2+ 2H2O→2Fe2O3∙H2O
Fermentation
C6H12O6→2C2H5OH + 2CO2



A bit of Chemistry for you

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CHEMISTRY--------Atomic structure
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a) Atoms can be represented as shown in this example for sodium Na:
*.
Mass number 23, Atomic number 11,
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b) The relative masses of protons, neutrons and electrons are:
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Name of particle and mass: Proton 1, Neutron 1, Electron Very small~1/2000
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c) The total number of protons and neutrons in an atom is called its mass number.
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d) Atoms of the same element can have different numbers of neutrons;these atoms are called isotopes of that element.
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e) The relative atomic mass of an element (A r ) compares the mass of atoms of the element with the 12 C isotope.
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It is an average value for the isotopes of the element.
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f) The relative formula mass (M r ) of a compound is the sum of the relative atomic masses of the atomsin the numbers shown in the formula.
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You are expected to use relative atomic masses in the calculations specified in the subject content.
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You should be able to calculate the relative formula mass (M r ) of a compound from its formula.
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g) The relative formula mass of a substance, in grams, is known as one mole of that substance.

A simple view of ionic bonding
The importance of noble gas structures
At a level (like GCSE) a lot of importance is attached to the electronic structures of noble gases like neon or argon which have eight electrons in their outer energy levels (or two in the case of helium). These noble gas structures are thought of as being in some way a "desirable" thing for an atom to have.
You may well have been left with the strong impression that when other atoms react, they try to organise things such that their outer levels are either completely full or completely empty.
Ionic bonding in sodium chloride
Sodium (2,8,1) has 1 electron more than a stable noble gas structure (2,8). If it gave away that electron it would become more stable.
Chlorine (2,8,7) has 1 electron short of a stable noble gas structure (2,8,8). If it could gain an electron from somewhere it too would become more stable.
The answer is, If a sodium atom gives an electron to a chlorine atom, both become more stable.
The sodium has lost an electron, so it no longer has equal numbers of electrons and protons. Because it has one more proton than electron, it has a charge of 1+. If electrons are lost froman atom, positive ions are formed.
Positive ions are sometimes called cations.
The chlorine has gained an electron, so it now has one more electron than proton. It therefore has a charge of 1-.If electrons are gained by an atom, negative ions are formed.
A negative ion is sometimes called an anion.
The nature of the bond
The sodium ions and chloride ions are held together by the strong electrostatic attractions between the positive and negative charges.
The formula of sodium chloride
You need one sodium atom to provide the extra electron for one chlorine atom, so they combine together 1:1. The formula is therefore NaCl.

The Group 1 elements - Multiple choice- Test
1 .
Why are the group 1 elements stored under oil?
A.To stop them from floating
B.To stop them reacting with air or water
CSo that they can be seen more easily
2 .
What products are formed when lithium reacts with water?
A.Lithium oxide and water
B.Lithium hydroxide and hydrogen
C.Lithium hydride and oxygen
3 .
What colour flame is produced when potassium reacts with water?
A.Orange
B.Red
C.Lilac
4 .
The alkali metals all have similar properties because:
A.Their atoms all have one electron in their outer shells
B.They have similar atomic numbers
C.They are all in the periodic table
5 .
What colour is produced by a lithium compound in a flame test?
A.Brick Red
B.Orange
C.Green
6 .
The correct order of reactivity, starting with the most reactive, is:
A.Potassium then sodium then lithium
B.Lithium then sodium then potassium
C.Sodium then lithium then potassium
7 .
The correct balanced symbol equation is:
A.Cs + H 2 O → CsOH + H
B.2Cs + 2H 2 O → CsOH + H 2
C.2Cs + 2H 2 O → 2CsOH + H 2
8 .
Choose the correct statement about the elements in group 1:
A.They all produce an acid when reacted with water
B.They all produce an alkaline gas when reacted with water
C.They all produce an alkaline solution when reacted with water
9 .
The loss of electrons is an example of:
A.Oxidation
B.Reduction
C.Neither oxidation or reduction

Group 1 Metals
Quick revise
The elements in Group 1 of the PeriodicTable are called the alkali metals. Theyinclude lithium (Li), sodium (Na) and potassium (K).
Physical Properties
*. Easy to cut
*. Shiny when freshly cut
*. Low density
Chemical Properties
*. Metals are very reactive with chemical reactivity increasing down the group.
*. All the metals react :
*. :with oxygen to form oxides e.g. Li 2 O
*. :with water to form hydroxides and hydrogen e.g. KOH
*. : with halogens to form halides e.g. NaOH
Alkali Metal Compounds
*. All alkali metal compounds are stable, this is because the alkali metals are so reactive.
*. Alkali metals have to be extracted from their ores by electrolysis
*. Alkali metal compounds are usually colourless
*. The hydroxides are strong alkalis