Saturday, July 17, 2010

Key Concepts

An oxidation number (oxidation state) is the charge an atom would carry if the molecule or ion were completely ionic.

Rules for Assigning Oxidation

Numbers

Fluorine is assigned an oxidation number of -1 in compounds
HF oxidation number of fluorine = -1
Oxygen is assigned an oxidation number of -2 in compounds
H₂O oxidation number of oxygen is -2
Except
- Peroxides: oxidation number of oxygen is -1
  H₂O₂ oxidation number of oxygen is -1
- Superoxides: oxidation number of oxygen is -½
  KO₂ oxidation number of oxygen is ½
- Oxygen fluorides: OF₂ oxidation number of oxygen is +2
  O₂F₂ oxidation number of oxygen is +1
Hydrogen is assigned an oxidation of +1 in compounds
HCl oxidation number of hydrogen is +1
Group I elements (Alkali Metals) are assigned an oxidation number of +1 in compounds
NaNO₃ oxidation number of sodium is +1
Group II elements (Alkaline-earth metals) are assigned an oxidation number of +2 in compounds
MgBr₂ oxidation number of magnesium is +2
An atom of any element in the free state has an oxidation number of 0
S₈ oxidation number of each sulfur atom is 0
Any monatomic ion has an oxidation number equal to its charge
H^- oxidation number of hydrogen is -1
The sum of the oxidation numbers of all the atoms in a formula equals the electrical charge shown with the formula
- The sum of the oxidation numbers of all the atoms shown in a formula of a compound is 0
  CO₂: let x be the unknown oxidation number of carbon
  0 = x + (2 x -2)
  So x (oxidation number of C) = 0 + 4 = +4
- The sum of the oxidation numbers of all the atoms shown in the formula for a polyatomic ion or complex ion equals the electrical charge on the ion
  Cr₂O₇^2-: let y = unknown oxidation number of chromium
  -2 = 2y + (7 x -2)
  2y = -2 + 14
  2y = +12
  y (oxidation number of Cr) = 12 ÷ 2 = +6

rained @ 12:13 AM

Monday, July 12, 2010

Transition metals!
What are they?
The 38 elements in between group II and group III of the periodic table are called transition metals.The name 'transition' derives from their position in the periodic table, as they act as a transition ['bridge'] between the group II and group III elements.

Uses of transition metals...:)
Some transition metals have several uses, especially for iron and copper. Transition metals also often form important alloys like iron in steel, zinc & copper in brass.

Transition metals are good catalysts for particular reactions.
[Note: Catalysts are substances that can be used to change the rate of a reaction.They are usually used to speed up the rate of a reaction. The catalyst itself is not involved in the reaction itself, so it is not changed or used up during the reaction.It stays in its original form even after the reaction is complete! :D]

The bonding of atoms in transition metals is relatively strong.As a result, they are strong metals with high boili

ng and melting points as well as high densities.They also have many electrons to carry energy, thus are effective in conducting electricity

. Many of the transition metals are not very reactive to water or oxygen, but when they form salt compounds, the resulting substance tens to be coloured.For example, cobalt chloride is blue and titanium chloride is purple.

[THEREFORE THEY ARE VERY COLOURFUL METALS!!! YAY! :DDD]

References~!
http://www.ehow.com/about_5366616_uses-transition-metals.html

http://www.gcsescience.com/pt21.htm
http://en.wikipedia.org/wiki/Transition_metal

Labels: catalysts, Transition metals

rained @ 1:08 AM

Sunday, July 11, 2010

Hydrogen

Bomb

The Hydrogen bomb works on a physical principle known as nuclear fusion. In nuclear fusion, the nuclei of atoms join together, or fuse to form a heavier nucleus. This happens only under very hot conditions. The explosion of an atomic bomb attached to a hydrogen bomb provides the heat to start the fusion.Hydrogen nuclei fuse to form helium and as this happens, huge amounts of energy are released from the hydrogen nuclei, producing a huge explosion.

Fusion releases energy due to the overall loss in mass. If you add up the masses of the particles which go into a fusion reaction, and you add up the masses of the particles which come out, there is frequently a difference. According to Einstein's famous law relating energy and mass, the "mass difference" can take the form of energy.

Fusion reactions involving nuclei lighter than iron typically release energy, but fusion reactions involving nuclei heavier than iron typically absorb energy. The amount of energy released depends on the specifics of the reaction. The reaction used in the hydrogen bomb, though, produces one of the greatest changes in mass.

The hydrogen bomb is thousands of times more powerful than an atomic bomb. There have not been any hydrogen bombs used in warfare, however there have been hydrogen bomb tests. Most of these tests are done underwater due to risk of destruction. To give you an idea of how strong the H-bomb is, think about this. This atomic bomb dropped on Hiroshima, Japan which killed over 140,000 people had the power of 13 kilotons. A common hydrogen bomb has the power of up to 10 megatons. All the explosions in World War II totalled "only" 2 megatons -- 20% of the power of ONE common hydrogen bomb.

http://www.cartage.org.lb/en/themes/sciences/Physics/NuclearPhysics/Applications/NuclearWeapons/NuclearWeapons.htm

rained @ 6:50 AM

Molecular Orbital Theory

When simple bonding occurs between two atoms, the pair of electrons forming the bond occupies an MO that is a combination of the wave functions of the atomic orbitals of the two atoms involved.

When atoms combine to form a molecule, the number of orbitals in the molecule equals the number of orbitals in the combining atoms. When two very simple atoms, each with one atomic orbital, are combined, two molecular orbitals are formed. One is a bonding orbital, lower in energy than the atomic orbitals, and derived from their sum. It is called sigma. The other is an antibonding orbital, higher in energy than the atomic orbitals, and resulting from their difference.

www.chemistryexplained.com

rained @ 6:35 AM

What are ISOTOPES??
Isotopes are atoms of the same elements but having a different number of neutrons or mass number.However, the atomic number or the number of protons stays constant and does not ever change as it is what makes the elements unique from each other.

An example of isotopes originate from carbon.The original state of carbon atoms is actually Carbon-12. However some carbon atoms actually have some extra or less neutrons than 12.Some may have 7, some 8.Those are examples of isotopes.

Some isotopes are stable, but others are radioactive (unstable). An isotope is radioactive if its nuclei are unstable. Large atomic nuclei, with more than 83 protons and their associated complement of neutrons, are unstable. Uranium and plutonium are examples of such elements. Small atomic nuclei may also be radioactive if the ratio of neutrons to protons exceeds certain limits. Even tiny hydrogen, the smallest of atoms, has a radioactive isotope.Radioactive isotopes have certain uses, such as in agriculture application and they have medical uses as well.

en.wikipedia.org/wiki/Isotope

www.pa.msu.edu/sciencet/ask_st/060194.html

www.chem.duke.edu/~jds/cruise_chem/nuclear/uses.html

rained @ 3:58 AM

Wednesday, May 5, 2010

Alimentary Canal :)

:)

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Mouth: pH7.Tongue rolls food into a bolus.Chewing and grinding of food into smaller pieces takes place here. Both chemical and mechanical digestion takes place. Starch digestion starts here, the enzyme salivary amylase is released here, and starch becomes maltose. Maltose is then broken down into glucose with the help of the enzyme maltase.

Oesophagus: Starch digestion continues. Food is pushed down and travels down to the stomach by the oesaphagus.

Stomach: pH2. Hydrocloric acid makes the conditions of the stomach acidic. Therefore it is suitable for the enzyme pepsin to act on proteins.Protein digestion begins here. With pepsin acting on them, proteins are broken down into amino acids.

Small intestine:pH9(For duodenum and jejunum).All three sources of energy are digested here.Fat digestion starts here. Enzymes trypsin, pancreatic amylase,maltase and lipase is released. Fat is turned into 1 glycerol and 3 fatty acids by lipase. Again, starch is digested by pancreatic amylase into maltose, which is then turned into glucose.Protein is broken down into amino acids.
Ileum--- Absorption of digested food substances. Villi present on the walls of the ileum, and micro-villi (multiple folds) in the villi, to increase the surface area for quick diffusion.The villi is also supplied with a network of capillaries for quick diffusion. The food then passes through the hepatic portal vein.

Large intestine: Absorption of water..

rained @ 4:44 AM

Thursday, March 25, 2010

Should we eat cooked or raw food?

In almost every meal of ours, the food is cooked. Heat is of course exposed to the food, but this burns the nutrients in the food, and makes it toxic. The harmful effects of these burnt nutrients accumulate over the years. Humans are also actually biologically adapted to raw fresh food.
What's more, when cooking food and too much heat is applied, important nutrients are lost in the process. We do not obtain the nutrients we could have obtained from the food we eat as it was cooked. Therefore, to have a healthy life, we should eat raw foods rather than cooked foods as they are better for our health.

rained @ 6:45 AM

Wednesday, March 24, 2010

Is cooked or raw food digested faster?

Raw food co

ntains enzymes for digesting food. When raw food is exposed to high heat and temperatures , they break down quickly. One of the constituents of food that can be broken down is enzymes. These enzymes are essential and play an important role, they help us to digest our food.

When enzymes are heated, their structure changes and they can no longer function as they were supposed to,so our body has to produce our own enzymes to digest cooked food. Valuable metabolic enzymes are therefore used to digest cooked food,so digestion of cooked food requires more energy than digestion of raw food. Therefore, raw food is digested faster than cooked food.In fact, raw food travels through the digestive system two to three times faster than cooked food does.

rained @ 6:31 AM

Sunday, February 21, 2010

Some safety rules whe

n using electricity...

Do not overload a power socket.This may cause large currents to flow and generate lots of heat, resulting in a fire.

Never stick / poke anything into an electrical socket.You would be at a high risk of electrocution.

Do not use appliances with damaged insulation.Replace it immediately.The wires may be exposed, and current may flow into anything it comes into contact with.

Do not wet electrical appliances, plugs or sockets.Remember? Water is also a conductor of electricity so if you use wet appliances the water may conduct electricity into your body, which is highly dangerous.

Never use electrical appliances near or in wet areas.

Disconnect appliances when cleaning them.

Call the electrician to replace or repair appliances if you are unsure how to do so.If not, you may get hurt while trying to repair them.

rained @ 4:03 AM

Saturday, February 13, 2010

Electric circuits
When various electrical components are connected together, they form a circuit.
For example, a circuit could consist of a switch to turn current flow on and off, a dry cell to provide energy, an appliance (eg. light bulb) and wires to connect the components.

Electrical circuits can be drawn using symbols.

There are two main types of circuits - series and parellel.
In series circuits, there is only one path for current to flow through, so if one bulb blows the rest also do not light up.

In parallel circuits, the electric current is divided into branches, and current is split up equally between each branch.If one bulb blows the other can still work fine.

An ammeter is used to measure current, and it must be connected in series with the circuit.

Potential difference

This is the amount of energy needed to move one unit charge of electricity from one point to another.
Potential difference is measured in volts, and the unit for it is (V).

A voltmeter is used to measure potential difference, little or no current goes thorugh it therefor it cannot be used to measure current.
It must be connected in parellel in the circuit.

The electric charges flow from a higher potential difference to a lower potential difference.

Resistance

Electric current does not flow smoothly throughout the whole circuit, as the components resist the flow of the electrons.This resistive force is called resistance. The unit for resistance is ohms.To calculate resistance, you can take V/I which is equals to R , resistance.

There are both fixed and variable resistors.
Fixed resistors have a fixed resistance value.
As for variable resistors or rheostats, the current can be varied, therefore varying the resistance.

Effects of an electric current

Electricity is a form of energy, and it can be converted to other types of energy.This makes our lives much more convenient.

Heating effect of a current

When a current passes through a wire, the wire heats up as caused by electrical energy being converted to heat energy.
Heating appliances have coils or heating elements, and they heat up when electricity passes through them. This heat is used for ironing, boiling, cooking,etc.

Lighting

effect of a current

The heating effect of a current can lead to another effect, which is the lighting effect. In a light bulb, the heat generated is so great that the filament starts to glow and give out light, which is how a bulb lights up.

rained @ 12:51 AM

Electricity

Electric current

For electrical appliances to work, enough electricity must flow through it.This flow of electricy is due to the flow of electric charges.They can be both positive and negative.When these charges move, they form an electric current.
Electric current is the rate of flow of electric charges.The path in which current flows is called a circuit.

Current is represented by the symbol (I).

Very irritating fact caused by CONVENTION that everyone was arguing about.

Electric current is due to the flow of electrons in a circuit.Electrons move from the negative terminal of a dry cell its positive terminal. However, when scientists discovered current flow, thye did not know that electrons existed. They all thought current flowed from the positive terminal of a source to the negative terminal.This is known as the conventional current flow.

AFTER electrons were discovered, they found out that current actually flowed from the negative terminal to the positive. But conventional current is still used to understand circuits.

(Our big question : Why do we still use the conventional current to learn about circuits when we actually already know now that current flows from the negative to the positive terminal of a cell?! Why can't they just change and standardise it to the electron flow, which is actually correct? -.-)

rained @ 12:21 AM

Monday, February 8, 2010

Why should we NOT touch or use switches when our hands/fingers are wet?

As we all know, water is also a good conductor of electricity, other than materials like metal. If we touch a switch with our wet hands, the water might just be closing the circuit, as a result causing electricity to flow through the 'circuit' in which your hands are part of. This gives you an electric shock and if it is very serious it may lead to dire consequences.

rained @ 6:28 AM

Monday, January 25, 2010

Dispersion of white light
Sunlight is actually made up of seven different colours although it appears white.
Light can be dispersed using a glass prism. When light shines through a glass prism, the light leaves the prism and disperses into seven colours.The seven colours are red, orange, yellow, green, blue, indigo and violet.

The colour that bends the least is red, and the most violet.This is because red travels the fastest. When light passes throught the prism, the seven colours are dispersed and they travel at different rates.

rained @ 1:16 AM

Sunday, January 24, 2010

Light
Light comes into your eyes and not OUT OF your eyes.OUR EYES ARE NOT A LIGHT SOURCE.
Light travels in straight lines.
Reflection

The angle of incidence is the angle between the normal and the incident ray.
The angle of reflection is the angle between the normal and the
reflected ray.

There can be regular reflection or diffused/irregular reflection.
Regular reflection occurs when light shines onto a smooth surface,

and a clear image appears.The rays reflected are parellel.
Diffused reflection occurs when light shines onto a rough surface and there is no reflective image.The rays reflected are scattered.

Refraction
Involves de

nsity and speed.
Light bends when a light ray travels from one medium to another of a different density (such as from air to water) , and this bending of light is called refraction.
As light enters a medium of higher density, it slows down and bends towards the normal.
For example, light enters glass, a medium of higher density, so it slows down and bends towards the normal.When it travels through the glass and enters air once again, it speeds up and bends away from the normal.

rained @ 11:49 PM

Monday, January 11, 2010

Are sport

s drinks acidic?
Yes,apparently they are.Most of them contain citric acid.

rained @ 11:43 PM

Tuesday, January 5, 2010

Why can't the button on the lift work if something is covering your finger(eg. gloves/plaster)?
I think its because of the material of the fabric that causes you to be unable to press the button..Or maybe to press the button it needs to sense heat before it lights up and everything.And if you wear gloves/plasters,the fabric 'blocks' or absorbs the heat and therefore no heat is sensed at the button.

Why does ice 'stick' to your fingers when you take it out of the refridgerator?
First,we have to look at the formation of ice.Ice is the solid state of water,so we look at the formation of water.

Water (H2O) is made up of two molecules of hydrogen and one molecule of oxygen. But oxygen has the two extra pairs of electrons which are known as lone pairs.Every molecule in the water is attached with the nearby molecule through hydrogen bonding.When water is in liquid state every molecule changes its interaction and makes new connections with new molecules which results in water flow. However in its solid state(ice) it cannot break old connections and form new ones.Now the molecules are not in the condition to change their interactions so they remain in one place forming a three dimensional hydrogen bonding.

On the surface of ice some oxygen atoms and hydrogen atoms are left facing outwards which causes them not to connect with the other molecules to form hydrogen bonds. So they are looking for a partner to form the bond.When a surface that is able to form this bond comes in contact with the ice surface it will stick to that, like our skin. Our skin has high moisture content and very appropriate to form the bond with these atoms that is why it sticks to your skin when you touch it.

http://www.letusfindout.com/why-does-ice-stick-to-your-skin/

rained @ 2:18 AM

Wednesday, November 25, 2009

Transport in living things
- Diffusion
- Osmosis

Diffusion is the overall movement of molecules of a substance from a region of higher concentration to a region of lower concentration.
For example,in leaves,carbon dioxide enters the leaves through the stomata,moving into air spaces in the leaves.This is because the carbon dioxide concentration is higher outside the leaves than in the air spaces in the leaves.

Osmosis is the net movement of water molecules from a region of higher water concentration to a region of lower water concentration through a partially permeable membrane.A partially permeable membrane is a membrane that allows some molecules to pass through but not others.
For example,when a plant cell is being placed in a beaker full of salt solution,the water in the plant cell will move out into the salt solution by osmosis as the concentration of water in the cell is higher than in the salt solution.

rained @ 11:19 PM

Friday, May 1, 2009

Separating Methods
Filtration
~separate an insoluble solid from a mixture
Evaporation
~separate a soluble liquid from a solution
Distillation
~simple
~fractional
Magnetic Attraction
(Paper)Chromatography
Desalination

Separation of Mixtures Method
Iron related material + another solid/solution Magnetic Attraction
Soluble solid + solution Evaporation
Insoluble solid + solution Filtration
Two miscible liquids(can dissolve in one another) Fractional Distillation

rained @ 12:01 AM

Thursday, April 30, 2009

Technology The application of scientific knowledge for practical purpose There are advantages and disadvantages of technology.For example:

Electricity Advantage: Useful for various appliances all over the world,most commonly used source of energy in the world Disadvantage:
Use of electricity exhausts the Earth's natural resources very quickly

Information
Advantage:
Easily available with technology

Disadvantage:
We may be exposed to negative media

Mobile Phones
Advantage:
Useful as communication tools
Disadvantage:
Excessive use of mobile phones may create health problems for users

Styrofoam
Advantage:
Can be used to make useful objects such as plates,cups,food containers,boxes and many others
Disadvantage:
May cause both health and environmental problems.

Benefits of technology
It has improved our lives in many ways
~the invention of medicines to fight diseases,to treat illnesses
~the development of food crops that are pest and disease resistant
~the invention of bicycles,automobiles,ships and aircraft for transportation
~the invention of telephones,mobile phones,computers,radios and television sets for communication and dissemination of information

Abuses of technology
Technology can cause harm to the society and environment,especially when misused
Loss of lives ~weapons such as guns and rifles ~harmful bombs made by terrorists to kill ~road accidents ~plane crashes ~sinking ships

Technology has its limits
It cannot solve all problems:
~inability to prevent natural diasters such as earthquakes and hurricanes from happening
~not all diseases have a cure

rained @ 9:49 PM

Lab Safety Rules
Do not enter or work in the laboratory unless a teacher is present.
Do not take apparatus or chemicals out of the laboratory without the permission of the teacher.
Always work quietly and thoughtfully.Horseplay,practical jokes and other acts of carelessness are strictly prohibited.
Do not store.prepare or consume food or drinks in the laboratory.
Always wear safety goggles when mixing,heating or handling chemicals.
Never pipette poisonous substances,hot solutions,or corrosive liquids by mouth.Use a pipette filler.
Do not take chemicals from unlabelled containers.Report such containers to the teacher.
Report to the teacher any damaged containers ,bottles or equipment.
Instructions for the performance of an experiment should be thoroughly understood and must be followed exactly.In any case of doubt,consult the teacher before proceeding.
Unauthorized experiments are forbidden.If you wish to conduct an experiment on your own,discuss it with your teacher and obtain his or her permission.
The storerooms and preparation rooms are out of bounds to all pupils.
Keep your bench tidy and uncluttered at all times.
Chemicals,once removed from the bottles,must never be put back inside the bottles unless instructed by the teacher to do so.
Never use flammable liquids near a naked flame.
Never taste chemicals or other materials unless specifically directed by the teacher.
Report all breakages,accidents and spillage immediately to the teacher.
Waste and surplus material must be disposed of properly,in accordance with instructions.
Wash hands thoroughly after all practical work.

rained @ 8:17 PM

Wednesday, April 8, 2009

Are there other versions of the periodic table?Yes!For example,this Chinese one..surprised?Anyway,how do they translate the names of the elements into chinese?Some of the names are so,how do you describe it,'chim'?

Why do we use symbols in the periodic table?

It is to enable everybody,regardless of their language,to understand as symbols are a universal language.

rained @ 6:04 AM

Compounds

Is a substance of 2 or more elements chemically combined.

A chemical reaction takes place when it is formed.

Energy in the form of light and heat are often taken in or given out during the chemical reaction.

When two elements are chemically 'combined together',it becomes a new substance.

It has properties that are different from its consttuent elements by chemical methods.

The different constituent elements are combined in fixed proportions.

rained @ 5:57 AM

Tuesday, April 7, 2009

ELEMENTS
They are the basic unit of all matter
An element is a substance that cannot be broken down into 2 or more simper substances by any
chemical method
There are 110 elements found on earth till now.
MIXTURES
Substances made up of two or more elements and/or compounds.
The constituents of a mixture are not chemically combined
No chemical reaction occurs when a mixture is formed
It has properties that are similar to its constituent elements that make it up
can be separated into its constituent elements without using any chemical methods.The different contsituent elements are mixed in varied proportions.

Energy in the form of light or heat is not required or given out during mixing.

rained @ 5:00 AM

Wednesday, April 1, 2009

the structure of benzene(it is complicated):

Benzene, or benzol, is an organic chemical compound and a known carcinogen with the molecular formula C6H6. It is sometimes abbreviated Ph–H. Benzene is a colorless and highly flammable liquid with a sweet smell and a relatively high melting point. Because it is a known carcinogen, its use as an additive in gasoline is now limited, but it is an important industrial solvent and precursor in the production of drugs, plastics, synthetic rubber, and dyes. Benzene is a natural constituent of crude oil, and may be synthesized from other compounds present in petroleum. Benzene is an aromatic hydrocarbon and the second [n]-annulene ([6]-annulene), a cyclic hydrocarbon with a continuous pi bond.

wikipedia.org

rained @ 6:02 AM

These are some hazard signs...read them carefully before using any chemicals..or else...

two 'X's,for harmful,there should be a letter 'h' beside it,for irritant,there should be a letter 'i' beside it

rained @ 5:53 AM

Friday, March 27, 2009

Overnight, Alaska's Redoubt volcano erupted with five large explosions. The National Weather Service has issued an Ashfall Advisory, with light ashfall already reported in some regions. Located about 100 miles southwest of Anchorage, Redoubt's last eruption occurred in 1989-1990, causing widespread mudfalls and coated Anchorage and other nearby areas with ash. The ash affected air traffic as far south as Texas. Redoubt’s 3,108-meter (10,197-foot) peak has been belching steam for several weeks, with seismologists anticipating a possible eruption. Visible evidence of increased volcanic activity appeared at the volcano’s summit from late January through February. Holes appeared in the ice, and streams of melt water cut across the surface of the Drift Glacier on Redoubt’s north flank.The four explosions were recorded at 10:38 pm and 11:02 pm local time on March 22, and then at 2:14 am, 1:39 am and 4:37 am local time on March 23.
An Ashfall Advisory for the Susitna Valley means that all will likely be deposited there, and residents are advised to seal windows and doors, protect electronics and cover air intakes and open water supplies.

rained @ 8:30 PM

Thursday, March 26, 2009

The tallest building in Singapore is the Swissotel,near the city hall MRT station.The Vertical Marathon was held there. There are 73 storeys and 1336 steps at Swissôtel The Stamford .
The tallest building in the world is the Taipei 101.Following it is the Petronas Towers 1&2 in Kuala Lumpur.Next,it is the Sears Towers in Chicago.Then,it is the Jin Mao Building in Shanghai.Lastly,it i the Empire State Building in New York.These are the top 5 tallest buildings in the world for now.Even taller buildings are now still under construction.

rained @ 8:08 AM

Tuesday, March 24, 2009

Chemistry(often called chim-mystery)
Inoraganic
-elements
-periodic table
Organic
-Usually related to biology
-polymers
-drugs
-perfumes
-alcohols
Physical
-rate of reaction
-heat
Computational
Spectrometry
Analytical
Sports science
-diet
-apparels
-physical
-mental skills

rained @ 5:37 AM

Thursday, March 12, 2009

Why some houses are painted white,but their door and window frames are black

The house can reflect the heat when the weather is hot to keep cool and the window and door frames absorb heat.However,when it is cold at night,the the black door and window frames radiate the heat so as to keep warm.

But the heat is also being radiated outside the house,instead of only into the house.Is there a way to prevent that?

rained @ 7:04 AM

Why is the freezer always(usually) on the top of the refridgerator?

The cold air sinks and the hot air rises.The hot air rises and 'goes' from the back of the freezer

into the freezer and the hot air becomes cold air.The cold air comes out and sinks when you open the freezer.That is why you can feel a gush of cold air on your face when you open the freeezer.

rained @ 6:55 AM