Grade 2 | SCIENCE
WEEK 11 • STUDENT TEXTBOOK • DAYS 51–55
Read each lesson with a parent or teacher and study the worked example. Then answer the questions for that day in the Week 11 Practice Workbook.
Week 11 Student Textbook | Week 11 Practice Workbook | Week 11 Teacher Guide | Week 10 Student Textbook | Week 12 Student Textbook | Grade 2 index
Day 51: Earth’s Surface Changes
The land around us is always changing. Wind, water and ice break rock into smaller pieces. This is called weathering. Then wind and water carry the pieces of rock and soil to new places. This is called erosion.
Some changes happen so slowly that people cannot see them happen. Others happen in minutes or hours. Scientists use many sources, such as photos, measurements and reports, to learn how fast a change happened.
Worked example: A river carries sand from a hill down to a lake. Is this weathering or erosion?
- Weathering breaks rock into pieces.
- Erosion moves the pieces to a new place.
- The sand is being carried to a new place.
Worked answer: Erosion.
Day 52: Slow Changes
Many changes to the land take a very long time. A river can carve a deep canyon by carrying away tiny bits of rock, year after year. The Grand Canyon in Arizona was carved by the Colorado River over millions of years.
Slow changes are hard to see in one day. Scientists find evidence of them by measuring the same place many times and comparing old photos with new ones.
Worked example: A path in a park wears down a little more each year as people walk on it. Is this a slow change or a fast change?
- The path changes a little each year.
- You cannot see it change in one day.
Worked answer: A slow change.
Day 53: Fast Changes
Some events change the land very quickly. An earthquake can crack the ground in seconds. A landslide can move a whole hillside in minutes. A flood can carry away soil and change a river’s path in a day.
A volcano can also change the land fast. On May 18, 1980, Mount St. Helens in Washington erupted. In one day, the top of the mountain was lowered by about 1,300 feet.
Worked example: A storm drops so much rain in one night that a creek overflows and carves a new ditch. Is this a slow change or a fast change?
- The new ditch formed in one night.
- That is a short time.
Worked answer: A fast change.
Day 54: Model Slow and Fast Changes
Scientists use models to study changes that are too big, too slow or too dangerous to watch up close. A sand hill can stand for a real hill, and water can stand for rain.
To make a fair test, change only one thing. In this test, both hills get the same amount of water. Only the speed of the water is different.
Worked example: Why should both sand hills get 1 cup of water?
- The test is about how fast the water comes, not how much.
- Using the same amount of water keeps the test fair.
Worked answer: So that only the speed of the water is different.
Day 55: Independent Check: Slow and Fast Changes
Today you will answer on your own.
Use what you learned this week: weathering and erosion, slow changes, fast changes, and evidence from tables and reports.
Worked example: A beach loses a little sand each year to the waves. Is this a slow change or a fast change?
- The beach changes a little each year.
- The change cannot be seen in one day.
Worked answer: A slow change.
Week 11 Student Textbook | Week 11 Practice Workbook | Week 11 Teacher Guide | Week 10 Student Textbook | Week 12 Student Textbook | Grade 2 index