ARTICLES CO-OB

PREPARING LIME WATER.

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Dissolve some calcium hydroxide (lime used in betel chewing) in water. When you filter this solution with a filter paper you get lime water. It is a colourless solution. A white layer could be seen if the lime water solution is exposed to air.

SENT CARBON DIOXIDE INTO LIME WATER.

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When carbon dioxide gas is sent to lime water, calcium hydroxide in lime water reacts with the gas giving white calcium carbonate which is insoluble. The solution becomes milky due to this. If we pass carbon dioxide continuously, calcium bicarbonate which is soluble is formed. The the solution become clear again.

PROPERTIES OF CARBON DIOXIDE

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CARBON DIOXIDE GAS IS,

1.IS colour less,

2.Has specific odour,

3.Is heavier than air,

4.Is a non – supporter of combustion,

5.Turns lime water milky,

6.Have fire exitinguishing properties.

CARBON DIOXIDE IS A NON SUPPORTER OF COMBUSTION

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IDENTIFICATION OF CARBON DIOXIDE

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Introduce a small amount of lime water into a jar with carbon dioxide prepared in the page number 19 and shake it. Clear lime water turns milky. This can be used as a test for carbon dioxide.

PREPARATION OF CARBON DIOXIDE

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COLLECTION OF CARBON DIOXIDE GAS

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When collecting carbon dioxide the gas jar is kept upwards and the delivery tube is placed in it. Here air is displaced upwards the gas gets collected. This method of collecting gases is called the “upward displacement of air”- gases denser than air can be collected by this method. We can cover the gas jar with gas jar lids and can be used for further activities.

USES OF CARBONDIOXIDE

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This has which is about 0.03% of the atmosphere is of great use. Some instances are given below.

1.When soda and sweet drinks are produced, this gas is dissolved in them under high pressure.

2.For fire extinguishing purposes.

3.To make dry ice as a cooling agent and producing artificial rain (dry ice is solid carbondioxide produced by solidifying carbondioxide under high pressure).

THE METHOD OF BALlOON FILLED WITH HYDROGEN

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Bory the bottle about 2/3rd in the soil. Put aluminum pieces and caustic soda into it. Add hot water to the bottle. Fix the balloon to the bottle. The balloon will be filled with hydrogen. Tie the mouth of the balloon and remove it from the bottle. Release the balloon in to the atmosphere. You would be surprised to see the balloon rising up.

PROPERTIES OF HYDROGEN GAS

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Hydrogen gas is :-
1.Is colourless,
2.Has no specific odour,
3.Is slightly soluble in water,
4.Is inflamable,
5.Is ligterthan air(less dense)

ITENDYFYING THE HYDROGEN GAS

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Observe the colour and odour of a hydrogen sample you collected.

Close one boiling tube filled with hydrogen with a glass plate and hold its mouth upwards. Then insert a lighted taber into it as you open the lid.

The gas burns with a ‘pop’ sound. This shows that hydrogen is an in flammable gas.

PREPARATION OF HYDROGEN

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COLLECTION OF HYDROGEN

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When hydrogen gas is collected in the boiling tube, the air inside the tube is displaced downwards. This method of collecting gases is called the the DOWNWARDS DISPLACEMENT OF AIR. Light gases which are less heavier than air are collected by this method.

Hydrogen does not dissolve much in water. Therefore it can be collected over water too.

USES OF HYDROGEN

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The Sun

The Sun outshines everything else in the sky. Hydrogen makes up the bulk of the Sun and provides fuel for the nuclear reactions that make the Sun shine.

Horsehead Nebula

Stars are born from nebulas like the Horsehead Nebula, which is more than 1,000 light-years from the Earth. The nebula consists mainly of hydrogen gas. Hydrogen is the most common element in the universe.

PROPERTIES OF OXYGEN

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OXYGEN GAS IS,

1.COLOUR LESS
2.NO SPECIFIC ODOUR
3.SLIGHTLY SOLUABLE IN WATER
4.A SUPORTER OF COMBUSTION

COLLECTION and IDENTYFICATION METHOD OF OXYGEN

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COLLECTION METHOD OF OXYGEN

WHEN OXYGEN GAS COLLECT IN THE GAS JARS THE WATER IN IT MOVES DOWN AND GETS COLLECTED IN THE TROUGH. THIS METHOD IS NAMED AS COLLECTING GAS BY THE DOWNWARD DISPLACEMENT OF WATER. GASES THAT ARE INSOLUABLE or ONLY SLIGHTLY SOLUABLE IN WATER CAN BE COLLECTED BY THIS METHOD.

IDENTYFICATION OF OXYGEN

OBSERVE THE COLOUR AND ODOUR OF THE SAMPLE YOU COLLECTED. TURN THE GAS JAR UPWARDS AND INTRODUCE A GLOWING SPLINTER IN TO THE JAR AND IT WOULD REKINDLE. (LIGHT A TAPER OR EKEL AND BELOW OFF THE FLAME SO THAT ONLY THE GLOW REMAINS)IN THIS CASE THE GAS DOES NOT BURN, BUT THE GLOWING SPLINT ALONE REKINDLESTHIS SHOWS THAT OXYGEN IS NOT A COMBUSTIBLE GAS BUT ONLY A SUPPORTER OF COMBUSTION.

ANOTHER METHOD OF PREPARING OXYGEN GAS

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Preparation and collection of oxygen gas

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Photosynthesis

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Plants make their own food in a process called photosynthesis. Photosynthesis takes place inside plant cells called chloroplasts. Chloroplasts change sunlight, water, and carbon dioxide (a gas in the air) into sugars, a type of food used by the plant to grow. Photosynthesis also makes oxygen, which is released into the air.

Steel Production

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Molten pig iron is poured into a basic oxygen furnace (BOF) for conversion to steel. Steel is a form of iron produced from iron ore, coke, and limestone in a blast furnace. Excess carbon and other impurities are removed to make a strong steel.

USES OF OXYGEN GAS

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We may be knowing that oxygen gas in the atmosphere which is only 21% is needed by living things for respiration. Some instances in which oxygen is used are given below.

1.For the oxy-acetylene flame used in cutting and welding metals.

2.For diving.

3.For patients having breathing difficulties.

4.Matches burn because the material in their tips combines with an invisible gas, oxygen, in the air. Never play with matches—you might burn yourself or start a fire by accident.

Hard Disk

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The most commonly used device to storedata in the computer is the hard disk. This is fixed as a closed unit inside the computer.

There are different capacities in hard disk according to your requirment.

In hard disk, data are stored in platters and there can be several platters ina hard disk. All these platters are fixed on one spildle. All these are rotated together in the same speed whilw a resd / write head fixed in each platters separateley to read and write.

The speed of the hard disk is measured using its access time. This access time taken a vert small value andits measured in milliseconds (thousand unit per second)

ZIP DISK and JAZZ DISK

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ZIP DISK and JAZZ DISK are almost similar to floppy while the capacity them is several time larger than that of floppy. The capacity of the zip range from 100MB to 750MB. That mean, that the data of 500 floppy or morecan be stored in one zip. The capacity of jazz is 1 GB and 2 GB.

Floppy disk

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The floppy disk which are read and written in a very low speed in floppy disk and their capacity is very small compared to other data storage units. Floppy disk were produce various sizes such as 8, 5.25 and 3.5 incheswhile only 3.5 inches floppydick are available today.

One advantage of floppy disk is that they are portable. However\, since their capacity is small, moving the large filesused today here and there is in convenient.

Secondary storage unit(Auxiliary Memory)

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Secondary Storage Unitsare used to store data stedily and safely as required for a particular duration. Many secondary storage units areused to store data and given below are some of main units.