WATERS Mini Lesson s1

Measuring Concentrations of Insoluble Particles: Black Carbon in Snow and Ice A Yakima WATERS Mini Lesson

Targets and Assessment Lesson Parameters WA Science Standards Addressed: Content Area: Geology, Chemistry  6-8 PS2A – Substances have characteristic properties such as density, solubility, boiling Overview: Students will use the scientific method to point, and melting point. determine concentrations of “black carbon” (actually black  6-7 INQC – Collecting, analyzing, and displaying pepper) in “snow” (actually shaved ice) and apply this data data are essential aspects of all investigations. to describe how black carbon affects snowpack. This lesson is an extension to basic solubility lessons.

Grade Level: 8

Activity and Outcomes: Suggested Time: 1 50 min class period  Students formulate a hypothesis about black carbon transport and proximity to urban areas. Special Materials:  Students calculate concentrations of black  large (4’x6’) map of WA state pepper in ice samples.  Students report their findings by plotting the data in a graph.

Learning Outcomes: Knowledge:  Students will be able to define “insoluble particles” and describe what distinguishes them from soluble materials.  Students will be able to describe how black carbon is transported in the air.  Students will be able to describe how black carbon affects glaciers and snowpacks in the environment. Skill:  Students will be able to calculate concentrations of insoluble particles.  Students will be able to graph and interpret black carbon concentration data.

Science Concept Background: Particles that are insoluble in water are those that do not dissolve by dissociation or by the formation of hydrogen bonds with water molecules. Some examples of insoluble particles are dust, pollen, metal filings, sawdust, and black carbon. This lesson uses black carbon as an example of an insoluble particle because of its environmental significance and its potential impact on the hydrology of the Yakima River watershed, however the lesson may be adapted to treat any insoluble particle of interest. Black carbon, or soot, is formed during the combustion of fossil and bio-fuels. High concentrations of black carbon are found in the atmosphere near urban areas, especially recently industrialized areas where coal burning is prevalent and strict emissions policies do not exist. After it is created, black carbon resides in the atmosphere ~1-2 weeks before it is deposited on the ground, in lakes, on glaciers, or on snowpacks. When deposited on glaciers and snowpacks, black carbon reduces the reflectivity (albedo) of the snow or ice, causing it to absorb more solar radiation. This can affect the timing and magnitude of melt, which is important to communities that rely on seasonal snowmelt to supply fresh water. Materials:

 6 x Pre-prepared “snowpacks” spiked with “black carbon.” “Snow” can be made with an ice shaver, or substitute crushed ice. It is best to make the samples in bulk in closeable containers, which will be placed at different locations on the large map so that students can sample the snowpack. Spike each sample with “black carbon” by adding a known amount of ground black pepper to each bulk sample. Amounts may vary, but a minimum of 1g/ lab group / container for the low concentration samples and a maximum of 100g/lab group / container for the high concentration samples is an appropriate guide. Add the pepper by dusting the top of the ice uniformly. Close the bulk container and shake the pepper + ice mixture to obtain as uniform a concentration as possible. If it is too difficult to create a uniform concentration, consider using the averages of the concentrations from each lab group as the results.  1 x large (4’ x 6’ or larger) map of Washington state

1 bin per lab group (4 students per group) consisting of the following –  4 x test tubes  1 x cheese cloth, fine threads for straining small particles  1 x Bunsen burner, rubber tubing, striker, stand  1 x electronic balance  1 x Petri or ceramic dish  1 x graduated cylinder  1 x plastic funnel

Setup: Place the large map of WA State on the floor. Place each bin of black carbon at different locations across WA State. The high concentration “snow” should be nearer to Seattle/ Tacoma, grading to lesser concentrations as you move east. Lower concentration “snow” can also be placed West of Seattle in the Olympic Peninsula. Best if this is done RIGHT before students begin sampling the “snowpacks.”

Procedure: The first steps of the procedure are more suited for lecture or discussion format, and they correspond to the main points the students should be taught before beginning the procedure. The latter steps correspond to the hands-on lab activity.

1. Begin by engaging students’ prior knowledge of solubility and soluble substances. A quick demonstration that illustrates the difference between soluble and insoluble substances may be worthwhile. This may be as simple as demonstrating that salt dissolves in water but sand does not. Finish by having students brainstorm some insoluble substances/particles. It’s fine if students are thinking on a larger-than-particle scale here (e.g. wood, metal, rock, etc.). To segue to part 2, add black carbon to the list of insoluble particles. 2. Briefly explain how insoluble particles can become suspended in the atmosphere and have environmental consequences. Relate particle transport to students’ previous knowledge about air masses and prevailing wind currents. Examples of insoluble particles that have environmental consequences are pollen, dust, and lead. End the list of insoluble particles by describing black carbon and the scientific background included above. It is mainly crucial to explain what black carbon is and why we care about determining its concentrations in environmental samples of snow and ice. 3. But how to determine concentration? Here it is necessary to explain the concept of concentration: a measure of the mass of one substance divided by the volume of a different substance in which the first is dissolved or suspended. Emphasize that there is an important difference between concentration and density, even though the calculations are very similar and give the same units. This will be especially necessary if students have been covering density already in class. 4. Begin lab activity. Students formulate hypotheses about where the highest black carbon will be found. These sorts of hypotheses are not well phrased as “if, then” statements. Predictions are fine. The soundest predictions will state that the highest black carbon concentrations will be found in close proximity to Seattle because of its higher emissions. They will also touch on black carbon transport and its relation to prevailing wind patterns, in that black carbon concentrations will probably decrease as you move east from Seattle and be the lowest in the Olympic Peninsula because this location is west of Seattle (wind patterns generally blow east from the ocean). 5. Students decide where to “sample” the snowpack. They get to choose 4 samples out of 6 snowpacks. The sampling procedure is simply to fill one of their test tubes with “snow.” 6. While some students from each group are sampling the “snowpack,” other members of lab groups should set up Bunsen burners and cheesecloth filters. 7. Students begin melting samples over the Bunsen burner flame. Students should remove the test tube from the flame after the “snow” has completely turned to liquid. Students should not allow the sample to boil. 8. Have students filter the “black carbon” out of the sample using the cheesecloth and a graduated cylinder (to catch the water). A funnel may be necessary between the cheesecloth and graduated cylinder. Students should measure the volume of water that has been filtered. 9. After students have separated the black pepper from the liquid and let the pepper dry, they will transfer the black pepper to a Petri or ceramic dish and measure its mass. 10. Have students calculate concentrations of “black carbon” in each sample and report their findings by graphing the relationship between black carbon concentration and distance from Seattle. If the black pepper cannot be evenly distributed in the shaved ice, have the groups average the class data. Students should plot the data on a graph, which should be assessed by the teacher. Good graphs are those that are clear and properly labeled. Poor graphs are difficult to read or unclearly labeled.

Extension(s):

Knowledge of insoluble particles can be extended by performing the same procedure on samples spiked with different insoluble particles. A sample of a soluble substance can be included to emphasize the difference between soluble and insoluble substances.

The concept of concentration can be extended by teaching students about “parts per million” and “parts per billion.”

By: Andy (James) Menking, Fall 2011, for Morgan Middle School