WHAT IS COPPER?

Copper is a reddish-yellow metal. When it’s found in pure form in the ground it’s called native copper. Usually, though, copper is found combined with other elements in rocks. These rocks are called copper ores.

When combined with other elements, copper is often greenish in color. The Statue of Liberty is made mostly of copper. Its greenish color comes from copper combined with the element oxygen from the air.

Copper was one of the first metals discovered by human beings. People were making tools and jewelry from native copper over 10,000 years ago.

HOW COPPER IS USED

Pure copper is a soft metal. Early humans found that it made poor tools and weapons. They discovered that copper is much stronger when mixed with other metals. People made bronze by combining the metals copper and tin. They made brass by combining copper with zinc. Today, bronze and brass often contain other metals. But copper is still their main ingredient.

Copper has long been used for making coins. Copper coins were always less valuable than silver or gold coins, because silver and gold are rarer metals. Most coins used in the United States today contain some copper.

Copper sheets were once used to cover the bottoms of wooden sailing ships. They kept the wood from rotting or being eaten by sea animals.

Substances that contain copper are used to make blue-green inks and dyes. Other copper compounds are used as insect and weed poisons on farms or to purify water.

COPPER AND ELECTRICITY

Copper became more valuable in the late 1800s. That was when people discovered how to use electricity. Of all metals, copper is the second-best conductor of electricity. (Silver is better, but copper is much cheaper.)

Most copper mined today is used in the electrical industry. The wires in power lines are mostly copper. So is the wiring in electrical appliances and cords. Copper can be stretched into wires as thin as 0.001 inch (about 0.025 millimeters).

WHERE DOES COPPER COME FROM?

In ancient times, copper came mostly from the island of Cyprus in the Mediterranean Sea. (In fact, the name Cyprus means “copper.”) The ancient Egyptians, Greeks, and Romans made tools and weapons from Cyprus’s copper.

Native Americans used copper too. They mined copper in what is now Michigan. Copper ornaments from this region were traded all over America.

Today, much of the world’s copper comes from Chile. Arizona, Utah, and New Mexico are leading copper-mining states.

Coal is a black rock. It produces energy when it burns. The Chinese were mining and using coal for fuel over 3,000 years ago. It once powered the world’s industry. It helped make the United States a wealthy nation. Coal-burning trains carried people and products across the country. Today, coal-burning power plants produce electricity for many homes and businesses.

WHAT IS COAL?

Coal is mostly made up of the element carbon. When carbon burns, it releases a large amount of energy as heat. That’s what makes coal such a useful fuel.

Coal is a fossil fuel. That means it comes from the remains of ancient life buried deep in Earth’s crust. The coal we use today started out as plants that grew in swamps millions of years ago. When the plants died, they settled to the swamp bottom. Over time, layers of mud and rock formed. They compressed and hardened the plant material. Heat and pressure caused chemical changes. Gradually, the once-living matter became coal.

COAL MINING

Coal deposits are found in many parts of the world. Taking these deposits from the ground is called coal mining.

Some coal deposits lie close to Earth’s surface. They can be mined by scraping away the dirt and rock. This is called surface mining, or strip mining.

Other deposits lie deep underground. Miners must drill and blast deep holes in order to reach them. They bring machinery down to dig out the coal. This is called underground mining, or deep mining. Underground mines can be more than 1,000 feet (300 meters) deep. Their tunnels can be several miles long.

Deep mining is a dangerous job. Cave-ins, fires, and explosions are some of the dangers. Coal mining can also release poisonous gases. In the 1800s, miners would bring small birds into the mines as a safety alarm. If a bird died, it showed that there was poisonous gas in the mine. Today, miners use machines to test the air.

Surface mining is cheaper, easier, and safer than deep mining. But it scars the land. It can also create pollution and cause the soil to wash away.

HOW DO WE USE COAL?

A century ago, coal powered the steam engines that ran most machinery. Once, most American homes and office buildings were heated by coal-burning furnaces. Most of these jobs are now done by oil or natural gas.

Five-sixths of the coal mined today in the United States is used in electric power plants. Coal is also used in making iron and steel and in the cement- and paper-making industries.

PROBLEMS WITH COAL

Like other fossil fuels such as oil, coal is a nonrenewable resource. This means that once it’s used up, it’s gone. But the United States has a lot of coal. It would take hundreds of years to use it all.

Burning coal causes air pollution. Chemicals in coal can produce “acid rain.” Acid rain kills plants and pollutes rivers. However, machines called scrubbers can keep most of this pollution from getting into the atmosphere.

Burning coal also releases gases that cause global warming. These gases trap heat from the Sun. The trapped heat warms up the planet. Global warming could cause icecaps to melt and change Earth’s climate. Burning all of the coal available to us would be bad for the environment.