What is Coal?

Coal is a combustible sedimentary rock. It was formed millions of years ago when swamp plants died and fell to the ground. The swamp conditions prevented the plant material from decaying completely. Over time, the plant material was buried under layers of sand, soil, and rock. After millions of years under intense heat and pressure, coal was formed.

There are four different types of coal: Anthracite, Bituminous, Sub-bituminous, and Lignite. They each differ in the amount of carbon they contain and heat energy they can produce when burned.

• Anthracite coal (86%-97% carbon): Anthracite is the type of coal that creates the most heat. It is the hardest and most shiny of the types of coal. This is why it is often used to make steel and for producing electricity.

• Bituminous coal (45%-86% carbon): Bituminous makes up most of the coal found in America. It is black or dark brown, with lines of color that represent various minerals in the coal. It is very old, somewhere near 100 to 300 million years old. It is often used to make electricity and can help make various metals.

• Sub-bituminous coal (35%-45% carbon): Sub-bituminous creates less heat and is not quite as old as Anthracite and Bituminous. It sits in between lignite and bituminous and often contains less sulfur than other types of coal. This is why it is often used in electricity generation.

• Lignite (25%-35% carbon): Lignite is the type of coal that produces the lowest energy. It is a younger fossil fuel than all the others.

Sedimentary Rock in a Jar - A Coal Formation Activity

Sedimentary rocks are composed of different layers. These layers can be pebbles, sand, silt, or fossil fragments. Most sedimentary rocks such as coal are formed under the water and in swamps, lakes, seas, and oceans. In this activity, we will simulate the layer formation in sedimentary rocks.

Materials Needed:

• glass jars with lids

• water

• rocks

• pebbles

• sand

• soil

Procedure:

1. Collect rocks, pebbles, sand, and soil at school or home.

2. Fill a jar about one-third full with the rocks, pebbles, sand, and soil. Add water and shake.

3. Write a paragraph/statement about what you predict will happen and why.

4. Let the jar stand undisturbed.

5. Discuss what happened. Remember that sedimentary layers usually form in lake beds and near running water. After a long period of time, they will turn to rock.

6. Was your prediction proven or not? Why? Write that under your paragraph.

7. Enjoy re-shaking the jar and watching the materials resettle.