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Overview:
Students identify and compare four types of coal by examining and burning coal samples.
Objectives:
Students will:
- examine four unidentified types of coal and document their observations,
- observe how the four samples of coal burn, and
- draw a conclusion about the identity of each coal specimen.
National Standards:
National Science Education Standards (NSES)
- Science as Inquiry, 5-8
Abilities necessary to do scientific inquiry
- Physical Science, 5-8
Properties of matter and changes in properties of matter
- Science in Personal and Social Perspective, 9-12
Time Needed:
One class period
Materials:
Discussion Questions:
How many types of coal are there?
What are the distinguishing characteristics or properties of coal?
What test(s) can you perform in order to distinguish between the different types of coal?
Procedure:
- Begin by explaining to students that there are four major categories (or ranks) of coal: (1) lignite, (2) subbituminous, (3) bituminous, and (4) anthracite. Although peat is not actually coal, it is a brownish-black organic matter from which the other categories of coal are formed. In this experiment, students will examine samples of peat, as well as lignite, bituminous, and anthracite coals, as provided in the free kit from ACF. Review the following characteristics of each material that will be examined. (Note: These categories are listed by rank.)
- Peat: A brownish-black organic matter that looks very much like decayed wood, commonly used for peat moss, a garden mulch. Peat is not coal.
- Lignite: A brownish-black coal with generally high moisture and ash content and the lowest carbon content and energy value.
- Bituminous: A soft, intermediate grade of coal with carbon content and moisture between that of lignite and anthracite. It is the most common and widely used coal in the United States.
- Anthracite: The hardest type of coal, consisting of nearly pure carbon. It has the highest heating value and the lowest moisture and ash content.
- Give each student a Coal Identification Worksheet. Pass the coal samples around the room, allowing each student to examine the samples and take note of any evidence of plant matter, color, hardness, and luster. Encourage students to be as descriptive as possible on their worksheet in an effort to distinguish the specimens from one another. In other words, calling each specimen "brownish-black" is not specific; noting that "specimen 1 is darker than specimen 2" is preferable. Ask the students if they can correctly identify each sample. Have them hypothesize about the identity of each specimen and write their hypothesis on the worksheet.
- Remind students that visual appearance is not the only distinguishing characteristic of the various ranks of coal. Heating value is another significant property. Using tongs and wearing safety glasses, hold specimen 1 in a flame for the class to see. (Note: This is a good opportunity to explain the importance of lab safety. Tongs and safety glasses are essential equipment in working with fire.) Tell students to document the speed of ignition of the sample on the second chart of the worksheet. Remove the specimen from the flame and hold it so that the class can observe how it burns. Have one student use the stopwatch to time the burning of the sample. He or she should start the stopwatch once the specimen ignites and stop it when it has stopped burning. Meanwhile, tell students to record the flame color and any odor they detect. Repeat this process with each sample. Students may need to observe more than one sample burn before being able to describe the contrast in how rapidly each ignites.
- Have students work in pairs or small groups to consolidate and discuss their observations. Are they able to identify the specimens? Allow them to change their hypotheses about the identity of each specimen if they want to. Conduct a class vote about each specimen, asking students which type of coal they think it is. Have them discuss as a class their reasons for reaching this conclusion.
- Reveal the identity of each sample. Explain that the higher the rank of coal, the harder it is, the slower it ignites, and the longer it burns.
Assessment:
Have students prepare a summary of the experiment. Did their hypotheses change after they observed the samples being burned? At what point in the experiment did they become certain of the identity of each specimen?
Extension:
Encourage students to find out more about where each type of coal can be found in the United States. They can begin with the Coal Reserves map found in the All About Coal section. Have them follow up by finding out how much of a specific rank of coal has been mined in the past year and where.
Differentiation:
Some students may need to get closer to the experiment to get a better look at the burning specimens. Have them wear safety glasses if they do.
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