Chapter 5 form1

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CHAPTER 5


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Content

Activity


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The layer of air

surrounding the Earthconsists of a mixture ofgases.


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Air

Gases

Nitrogen

Carbon

Dioxide

Oxygen

Inert Gases

Othercomponents

Dust

Microorganisms

Water

Vapour


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Gas Percentage of gas content

Nitrogen 78%

Oxygen 21%

Carbon dioxide 0.03%

Inert gases and others 0.97%

Nitrogen

Oxygen

Carbon dioxide

Inert gases and

others


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An inactive gas.

Colourless, no smelland no taste.

Necessary for respiration,burning, rusting, and decay.

Released during respiration,burning and decay.

Absorbed by green plantsduring photosynthesis.

Example of inert gases are

helium, argon, neon, xenon,radon and krypton.

All these gases are nonreactive.


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When we leave a slice of bread outin the open for several days, what

happens to the bread?

The bread will turn mouldy. Themould shows the presence of

microorganisms in the air.In this case the fungi spores havesettled and started growing on thebread.


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The properties of oxygen and carbon dioxideProperties Oxygen Carbon dioxide

Solubility in water Slightly soluble Slightly soluble

Solubility in sodiumhydroxide solution

Not soluble Very soluble

Effect on glowingwooden splinter

The splinter ignites Oxygen supports burning

The splinter goes out Carbon dioxide does notsupport burning

Effect on burningwooden splinter

The splinter burns brighter Oxygen supports burning

The splinter goes put Carbon dioxide does notsupport burning

Effect on moist bluelitmus paper or moistred litmus paper

Oxygen has no effect onblue litmus paper or redlitmus paper

Oxygen is a neutral gas

Blue litmus paper : changesto red Red litmus paper : no change

of colour Carbon dioxide is an acidicgas

Effect on lime water No change Lime water turns cloudy

Effect onbicarbonate indicator

No change Changes the colour ofbicarbonate indicator fromred to yellow


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5.3 Oxygen is needed in respiration

oxygen

Food(sugar)

energy

Carbondioxide

water

1. The process where our body obtains energy from food is called respiration .2. During respiration , food in the form of sugar is oxidised by oxygen .3. The products of respiration are energy , carbon dioxide , and water vapour .4. Living things use the energy to carry out living processes such as breathing , moving

and reproduction.5. Carbon dioxide and water vapour are waste products that need to be removed from

the body .6. Living things obtain the oxygen needed for respiration through breathing .7. During breathing , living things take in oxygen from the air and remove carbon

dioxide and water vapour .

8. This explain s why the content of oxygen is more in inhaled air than in exhaled air.

Cell respiration requires oxygen


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5.4 oxygen is needed for

combustion

Combustion is a fast chemical reaction

between a substance and oxygen .

Oxygen supports combustion .

Combustion will only take place under

the following condition :

The presence of oxygen

The precence of fuel

Enough amount of heat is present

Heat energyLight energy


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What are the products of

combustion ?

Carbon + oxygen heat energy + light energy + carbon doixidecombustion

Hydrocarbon + oxygen heat + light + carbon + waterenergy energy dioxide

combustion

Conditions for combustion

Fuel


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5.5 Air pollution

Pollutants Effects

Dust

Soot

Smoke

Air become hazy

Low visibility

Breathing difficulties

Reduction in the rate of photosynthesis

Lead Damage to the brain or kidney

Carbon dioxide The temperature of the earth to rise

Sulphur dioxide

Nitrogen oxideTo form acid rain

Chlorofluorocarbon (CFC) Damage to the ozone layer


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Hello human !

We can prevent and control airpollution consist of two strategies ,

namely enforcement of anti-pollutionlaws and managing pollutants


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5.6 the importance of keeping the

air clean

Habits

that keep

the air

clean

You should

reduce short

trips . Walk .

Do not

smoke

Turn off the

engine of thecar while

waiting for

someone .Send your

motor vehicles

for regular

service to

reduce outputof polluting

exhaust gases .

Do notpractice open

burning .

Dispose of

your garbage

carefully


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Chapter 5 form1