Britannica Student Encyclopedia - 2010

Abu Dhabi became the permanent capital

of the federation in the early 1990s.

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United Arab Emirates

The Sultan Zayed Mosque in Abu Dhabi

was named for a longtime ruler of the

United Arab Emirates. The sultan was buried

in the mosque when he died in 2004.

BRITANNICA STUDENT ENCYCLOPEDIA Abu Dhabi 15

 

Abuja

Population

(2006 census),

Federal Capital

Territory,

1,405,201

Abuja is the capital of the African country

of Nigeria. It was built in the 1980s

to replace the crowded coastal city of

Lagos as the capital.

Abuja is located near the center of Nigeria

in an area called the Federal Capital

Territory. It is about 300 miles (480

kilometers) northeast of Lagos. The city

is built on the grass-covered Chukuku

Hills. The climate is cooler and less

humid than that of Lagos.

Abuja is divided into two zones. The

central area contains the government

buildings. The other zone provides

housing, shopping facilities, and other

services for the people who live there.

The government started planning the

new city of Abuja in 1976. It took more

than 10 years to build the city, but the

population grew even before it was finished.

Abuja officially became the capital

in 1991.

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Nigeria

Accra

Population

(2003 estimate)

1,847,432

Accra is the capital and largest city of the

West African country of Ghana. Its

name comes from the word nkran in the

Akan language. This refers to the black

ants that thrive in the area. Accra is situated

on the Gulf of Guinea.

Accra is the site of Ghana’s main government

offices. It is also the economic

center of Ghana. It contains the head

offices of all the country’s large banks

and trading firms. The city also has large

open markets. Its main products are

processed food, lumber, and textiles.

The city of Accra was formed in 1877.

By that time the British had gained control

of the whole area. It became known

as the colony of the Gold Coast. Accra

was the capital of the colony. The modern

city of Accra was carefully planned

and laid out between 1920 and 1930.

The Nigerian presidential palace is located

in the hills of the country’s capital, Abuja.

16 Abuja BRITANNICA STUDENT ENCYCLOPEDIA

 

When the Gold Coast gained independence

as Ghana in 1957, Accra

remained the capital.

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Ghana

Acid and Base

Acids and bases are two related groups of

chemicals. They are important to living

things and have many uses in industry.

Acids

Some acids are found in food. They

include acetic acid in vinegar, lactic acid

in milk, and citric acid in lemons. They

often have a sour taste. Other acids are

found in animals. The stomach makes

an acid that helps break down food.

Some acids do not come from living

things. These can be so strong that they

can corrode, or break down, metals.

They should not be tasted or touched.

Sulfuric acid is one example. It is used to

make fertilizers, dyes, drugs, explosives,

and certain batteries. When an acid is

dissolved in water the result is called an

acidic solution.

Bases

Bases may feel slippery in water. Some

are used in foods or medicines. These

often have a bitter taste. Examples of

bases include baking soda and milk of

magnesia. Other bases are used in

manufacturing. These are too strong to

be tasted or touched. Sodium hydroxide,

or lye, breaks down animal and plant

tissues. It is used to make soap, paper,

and artificial fibers. When water is combined

with a base the result is called a

basic, or alkaline, solution.

Acid-Base Reactions

When acids and bases are combined

they produce water and compounds

called salts. They have a salty taste and

none of the characteristic properties of

either acids or bases. The reactions

between acids and bases can be quite

strong. One result is that they can

quickly produce gases. This is why baking

soda is useful for baking pastries and

cakes. When it is combined with an acid

such as lemon juice or sour cream in a

dough mixture, it releases gases that

make the dough rise.

Identifying Acids and Bases

Acids and bases make some materials

change color. A special kind of paper

called litmus paper is one type of mate-

A strip of litmus paper shows

that a solution contains an acid.

If the solution contained a base

the paper would have turned

blue.

BRITANNICA STUDENT ENCYCLOPEDIA Acid and Base 17

 

rial that does this. An acid in water turns

litmus paper red. A base in water turns

the paper blue. A neutral substance,

such as pure water, gives litmus paper a

color midway between red and blue.

Acid Rain

Acid rain is a form of air pollution.

When coal and petroleum are burned in

automobiles, electric power plants, and

factories, they release certain harmful

gases into the air. These gases combine

with the oxygen and water in the air.

When the water in the air comes down

as rain, sleet, hail, or snow, it carries

with it these gases. This is known as acid

rain. Acid rain is very damaging to all

life forms.

Acid rain can pollute lakes and streams,

killing the fish and other organisms that

live in them. Acid rain also damages

various kinds of vegetation, including

farm crops and trees. In addition, acid

rain corrodes, or wears away, surfaces of

buildings and other structures.