Grade 2 | SCIENCE
WEEK 12 • TEACHER GUIDE AND ANSWER KEY • DAYS 56–60
Read each lesson aloud with the child and model the worked example before practice. Do not show this key during practice. Accept oral, drawn or written answers where the child cannot yet write the whole answer. On Day 60, read aloud if needed but give no hints.
Week 12 Student Textbook | Week 12 Practice Workbook | Week 12 Teacher Guide | Week 11 Student Textbook | Grade 2 index
Day 56: When Wind and Water Move the Land
Standard: Grade 2 Science Standard 11, 2.11
Practice record: Erosion problems, printed on the Week 12 Practice Workbook.
Worked example: A family’s garden soil washes into the street every time it rains. What is the problem? Worked answer: Water erosion is carrying the garden soil away.
- Waves.
- The farm field and the hill by a road.
- Example: People want to slow erosion on the farm field because crops need soil to grow. If the soil washes away, less food can grow. Accept any problem with a reason about harm to people, homes, roads or crops.
Teaching note: Walk around your home after a rain and look for places where soil has moved. Talk about what might keep it in place.
Day 57: Plants and Covers Hold Soil
Standard: Grade 2 Science Standard 11, 2.11
Practice record: Sample results, printed on the Week 12 Practice Workbook.
Worked example: Why do farmers plant grass on a bare slope? Worked answer: So the roots and leaves keep the soil from washing away.
- Pan A, bare soil.
- Pan B, covered soil.
- Both pans got the same water, but the covered pan lost very little soil and its water was only a little cloudy. The only difference was the cover, so the cover slowed the erosion. Accept any answer that compares the two pans and names the cover as the difference.
Teaching note: Do this test outdoors or in a sink. Use the observation checklist below.
Hands-on task observation checklist (Test a cover for soil). Check each item you observe. Four or five items shows the child met the task goal; two or three means repeat the task with support.
- ☐ Child set up both pans with the same slope.
- ☐ Child used the same amount of water on each pan.
- ☐ Child compared how muddy the water was.
- ☐ Child recorded the results for both pans.
- ☐ Child used the results to say which cover protected the soil better.
Day 58: Walls, Rocks and Windbreaks
Standard: Grade 2 Science Standard 11, 2.11
Practice record: Comparing solutions, printed on the Week 12 Practice Workbook.
Worked example: A town builds a pile of large rocks along a riverbank. What problem does it solve? Worked answer: It slows the river from wearing away the bank.
- A windbreak of trees.
- It costs a lot to build.
- A windbreak of trees, because the trees slow the wind before it reaches the soil. A rock wall or dam is for water, not wind. Accept a windbreak, or grass if the child explains that plants cover and hold the soil, with a reason.
Teaching note: Point out that no solution is perfect. Comparing the good points and drawbacks is how engineers choose.
Day 59: Test and Compare Solutions
Standard: Grade 2 Science Standard 11, 2.11
Practice record: Sample results, printed on the Week 12 Practice Workbook.
Worked example: Why should the hill be rebuilt the same way before testing the second barrier? Worked answer: So the only difference between the two tests is the barrier.
- The row of pebbles.
- The layer of leaves.
- The layer of leaves is like a cover of plants or mulch on real land. It slowed the water so it could not carry as much sand down the hill. Accept any answer that links the leaves to plants or a cover that slows water.
Teaching note: Results vary. Praise fair testing more than a winning design. Use the observation checklist below.
Hands-on task observation checklist (Design a barrier to protect a sand house). Check each item you observe. Four or five items shows the child met the task goal; two or three means repeat the task with support.
- ☐ Child designed two different barriers before testing.
- ☐ Child rebuilt the hill the same way for each test.
- ☐ Child used the same amount of water for each test.
- ☐ Child recorded how much sand reached the house each time.
- ☐ Child chose the better barrier and gave a reason from the results.
Day 60: Independent Check: Solutions to Erosion
Standard: Grade 2 Science Standard 11, 2.11
Practice record: Test of two hillsides, printed on the Week 12 Practice Workbook.
Worked example: Which slows wind: a windbreak or a dam? Worked answer: A windbreak.
- The bare hillside.
- 5 more buckets (6 – 1 = 5).
- Plant grass on the hill. The hillside with grass lost only 1 bucket of soil, but the bare hillside lost 6. Accept planting grass or another plant cover with the table as evidence.
Teaching note: Independent check: read aloud if needed, but give no hints.
Sources
USDA Natural Resources Conservation Service, Soil Erosion: Sheet, Rill and Wind Erosion (keep soil covered with plants or residue; windbreaks) | USDA National Agroforestry Center, Windbreaks (rows of trees and shrubs slow the wind and control soil erosion)
Week 12 Student Textbook | Week 12 Practice Workbook | Week 12 Teacher Guide | Week 11 Student Textbook | Grade 2 index
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