Measuring Concentrations of Insoluble Particles: Black Carbon in Snow and Ice
A Yakima WATERS Mini Lesson
Targets and Assessment
WA Science Standards Addressed:
 6-8 PS2A – Substances have characteristic
properties such as density, solubility, boiling
point, and melting point.
 6-7 INQC – Collecting, analyzing, and displaying
data are essential aspects of all investigations.
Lesson Parameters
Content Area: Geology, Chemistry
Overview: Students will use the scientific method to
determine concentrations of “black carbon” (actually black
pepper) in “snow” (actually shaved ice) and apply this data
to describe how black carbon affects snowpack. This
lesson is an extension to basic solubility lessons.
Grade Level: 8
Activity and Outcomes:
 Students formulate a hypothesis about black
carbon transport and proximity to urban areas.
 Students calculate concentrations of black
pepper in ice samples.
 Students report their findings by plotting the
data in a graph.
Suggested Time: 1 50 min class period
Special Materials:
 large (4’x6’) map of WA state
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