Geology of Table Rock - 7th - Pre-site Activities 2

Geology of Table Rock - 7th - Pre-site Activity/Teacher Led

Grade Level: 7
Content Area: Science
Time to Complete: 25 minutes
Title of Lesson: Demonstrating the Power of Water

South Carolina State Standards Addressed:

I.A.1.a.1.	Observe patterns of objects and events.
I.A.1.a.2.	Distinguish between qualitative and quantitative observations.
I.A.1.d.1.	Make inferences based on observations.
I.A.1.e.1.	Predict the results of actions based on patterns in data and experiences.
III.A.1.a.	Distinguish among weathering, erosion, and deposition.
III.A.1.b.	Examine how physical weathering and chemical weathering breaks rocks into fragments.
III.A.1.c.	Investigate and examine how the Earth's surface is constantly changing by weathering, erosion, deposition and human impact.
III.A.1.d.	Examine the effects of weathering, erosion, and deposition on the formation of major landform regions in South Carolina.
III.A.1.e.	Relate the fertility of floodplains to the deposition of sediments.
III.A.2.c.	Explain why soil (sediments) can be a major pollutant of streams.

Lesson Description:

Teacher will demonstrate examples of the power of water to weather rock/mineral fragments and to change their appearance. Teacher will then lead a class discussion about the power of water in mountain streams such as those found at Table Rock State Park.

Focus Questions For Students:

1.	How does a stream move material?
2.	What factors determine the power of a stream?
3.	In what ways does water act on rocks and minerals?

Culminating Assessment:

Students will write a short paragraph describing how they think the sediment in a stream at Table Rock State Park will appear.

4. Material/Equipment/Resources (Per Class):

coffee filters	large grained rock salt (special gravel)
distilled water or bottled water	ringstand
small, clear container with lid	sugar cubes
eyedropper	vocabulary list

Teacher Preparation:

1.	Read background information.
2.	Be prepared to discuss physical and chemical weathering.
3.	Wash glassware very carefully if students will be tasting water. Or use bottled water to perform the experiment.

Background Information:

Mountain streams are small but powerful. Due to significant drops in elevation over short distances their velocities, and erosive power, can be very high. Seasonal changes in rainfall and runoff also cause huge changes in the power of a mountain stream. With swift flowing water, mountain streams have the capacity to carry large bedload fragments. Fragments are continually being bounced and abraded-so much rounding takes place over time. However, being close to the source of sediment, mountain stream water is usually very clear.
   Sediment is transported by streams in three ways: dissolved load, suspended load, and bedload. Some of the dissolved load comes from soluble mineral material in the parent rocks, but most comes from the chemical alteration of the existing parent material. This process often releases soluble ions that are invisible but easily transported in the stream. The suspended load consists of small particles, mostly silt, clay, and sand. The particles are suspended above the stream bed as long as the water has enough turbulence to support them. Lastly, the large fragments of sand and gravel that cover the streambed and move only occasionally are called the bedload. The smaller bedload fragments move along by saltation, intermittent bouncing or skipping, while the larger fragments only roll or slide.
   Physical weathering, also called mechanical weathering, uses physical force or physical processes to cause the breakdown of rock and mineral material. Examples include the action by freezing and thawing water (frost wedging) and the action of heating and cooling (thermal expansion and contraction). Also included is the action of growing roots breaking and dislodging existing solid rock (biomechanical weathering), and the release of pressure as exposed rock that formed deeply underground at high pressure slowly expands and cracks (exfoliation).
   Chemical weathering causes breakdown and/or alteration of existing rock and mineral material by chemical means. Examples include the chemical bonding of oxygen to existing material (oxidation), the reaction of water to existing material (hydrolysis), and the reaction of an acidic solution with mineral material (carbonation). The action of water to dissolve soluble mineral substances is actually a physical process, although many textbooks include it in discussions of chemical weathering.

Procedures:

Part 1: Physical Weathering

1.	Show the students that the pieces of sugar are actually cubic in shape.
2.	Place 20 sugar cubes in a small container with a tight lid.
3.	Give the container to a student and instruct the student to hold the container tightly and swirl the contents while counting silently to ten. Do NOT shake it vigorously!
4.	Have them pass the container to another student who will repeat the swirling. Continue until each student in the class has swirled it. Note: While this is taking place proceed with Part 2. After the sugar has been returned to you set it aside. When you are done with Part 2, complete Part 1.
5.	Examine the sugar cube fragments. They no longer appear cubic, but rounded instead. There should also be a considerable amount of loose sugar in the container. This is an example of the power of abrasion to round particles within a stream.

Part 2: Chemical Weathering

1.	Set up a funnel on a ringstand with a small clear plastic cup underneath.
2.	Place a coffee filter in the funnel.
3.	Pour a few milliliters of distilled water into clear cup. Comment on its clarity.
4.	Use eyedropper to give a few students a drop to taste. Ask about its taste.
5.	Ask students to speculate if the look or taste of the water will change by filtering.
6.	Pour about 50 ml of distilled water through the filter.
7.	Ask if the appearance of the water has changed. Repeat taste test.
8.	Change coffee filter in funnel and place about 25 g of special gravel into filter.
9.	Repeat steps 6-7. Ask what the water did to the special gravel. Explain that this is an example of the power of water to chemically dissolve mineral material.