Grade 3 Science
Core Unit: Earth

Unit overview:

The structure of the Earth -- its core, mantle, and crust -- is described in this unit. The focus is on the soil, soil formation and development, and the topography produced by rearrangement of the soil and glacial till. The importance of soil is also considered.

Related material:

The grade 1 Core Unit, Earth, has introduced several of the important concepts in this unit. The lessons should be planned to build upon the experiences which the students had then.

The grade 2 Habitats Core Unit touches on the matter of topography as providing either habitat or appropriate sites for habitat development.

The grade 4 Core Unit on Fossils and Rocks further develops some of the concepts in this unit.

The importance of the soil to plant growth and animal habitat is one of the factors considered in the grade 5 Optional Unit of Communities and Ecosystems and in the grade 6 Core Unit, Ecosystems.

Suggested themes:

Earth, erosion, farming, glaciers, rocks, soil

Factors of scientific literacy which should be emphasized:

Common Essential Learnings foundational objectives which should be emphasized:

To promote intuitive, imaginative thought and the ability to evaluate ideas, processes, experiences and objects in meaningful contexts. (CCT)
To develop an understanding of how knowledge is created, evaluated, refined, and changed in science. (CCT)
To develop an understanding that technology both shapes and is shaped by society. (IL)

Science foundational and learning objectives:

Describe the structure of the Earth.
1. Recognize that the Earth is a sphere.
2. Identify the core, mantle, and crust as the layers of the Earth.
3. Describe the features of the core, the mantle, and the crust.
Describe some characteristics of the crust.
1. Observe and describe the surface features of the local area.
2. Observe and describe the composition of soil.
3. Identify types of soils by their components.
4. Describe the process of soil formation.
5. Recognize the importance of soil.
6. Consider the interdependence of agriculture and the soil.

Suggested Activities:

Have a globe, or several globes, in the classroom forhands-on study. The type recommended for use with this unit is one which illustrates the various physical features of theplanet in relief. Images from satellites can also be used to enhance the concept that the Earth is a sphere, and to compare with the regions shown on the globe. Videos which show the Earth from space would also be useful to help strengthen the concept of the spherical Earth. Plan ahead with resource centre staff to obtain globes, videos, and satellite images.
Using the globe, estimate the proportion of land to water. Estimate the amount of arable land of the total amount of land available. (In actual fact only 1/32 of the available land on Earth is arable. Of that arable land, much is quickly being lost to erosion, desertification, degradation, and urbanization.)
Factors: C6, C9, E4, G1
Objectives: 1.1, 1.3, 2.5
Assessment Techniques: 1, 3, 5, 8
Common Essential Learnings: Critical and Creative Thinking. The students become familiar with the spherical model of the globe. Since that model contradicts the intuitive sense that the earth is flat, the students learn that the evidence which may be the key to accurate perception is often difficult to obtain.
Observe the school yard, a field, or a vacant lot over a period of time, from several weeks to the whole year. Observe changes when a strong wind blows, or during and after a rain. Go on a hike and look for large scale changes caused by wind, rain, or other forces. Keep a journal containing records of what has been observed, and take photographs for a visual record. An album of the photographs can be passed from each year's class to the next, and a multi-year record of change produced.
Factors:B1, B2, B7, C5, C6, C9, C10, C12, F1, F4, G1
Objectives: 2.1
Assessment Techniques: 3, 4, 5, 6, 8, 9
Common Essential Learnings: Critical and Creative Thinking. This activity gives the students a chance to make long-term observations, to consider the data which they collect, and to formulate some hypotheses and questions about what they have seen.
Obtain some pebbles of sandstone or shale which are about 1cm to 5 cm in diameter. Sandstone or shale samples can be purchased from scientific supply houses. Both are easily identified, and can be gathered in most places in Saskatchewan. Locate lapidarists or rockhounds in the community who could help collect samples. A kit containing samples of many types of rocks found in Saskatchewan can be obtained from Saskatchewan Energy and Mines in Regina. These kits are useful in helping you and your students to identify the samples which you need.
Soak the pebbles in water for a day, remove them from the water, and put them in a plastic bag in a freezer. Remove them the next day and let them thaw for a day. Soak them again and return to the freezer. Repeat the cycle for several weeks. Examine the rocks periodically for evidence of change. Ask students to speculate whether soil left exposed in the winter is affected in the same way. Stress the importance of shelter belts and snow cover.
Fill a plastic pop bottle with water, cap it, and put it in a freezer. Observe the effect of freezing on the bottle. Ask students to speculate on why rocks emerge every spring on fields. Where do the rocks come from?
Factors:B1, B2, B7, C6, C8, C9, C12, F4
Objectives: 2.2, 2.3, 2.4
Assessment Techniques: 3, 5, 9
Common Essential Learnings: Critical and Creative Thinking. Here the hypothesis on the effect of freeze-thaw cycles is put to a test. The students can contrast the conditions under which this activity is done with those in nature, and practice in interpreting data.
Place some sandstone or shale pebbles of from 1 cm to 4 cm diameter into a plastic container, such as a margarine tub or yogurt container. Seal the lid securely with tape, and shake the container. Keep it in the classroom and encourage the students to take it outside to shake it. During an Arts Education class, it could be used as a percussion instrument. After a few hours of shaking, open the container and look for evidence of change. Continue the cycle.
Roll some large rocks down a hill. Look for evidence of change in the rocks, and on the soil and rocks which the rock rolled over.
Factors:B1, B7, C6, C8, C9, C10, C12, F3, G1
Objectives: 2.2, 2.3, 2.4
Assessment Techniques: 3, 5, 8
Common Essential Learnings: Critical and Creative Thinking. The students have a chance to evaluate the information which they are gathering through their observations.
Place a piece of white paper on a flat surface. Rub twopieces of sandstone or shale together over the sheet of paper. Look carefully at the paper and describe any residue which can beseen.Use a hand lens to examine the paper. Repeat the process usingtwopieces of granite, feldspar, or gneiss, with new paper for each trial. Then try a piece of sandstone and a piece of granite. All these rocks can be collected within Saskatchewan -- many of them in a typical gravel pit. See the note in activity 3.
Factors: B1, B2, B7, C1, C2, C8, C9, C12, F1, F3, G1
Objectives: 2.2, 2.3, 2.4
Assessment Techniques: 3, 5, 9
Common Essential Learnings: Critical and Creative Thinking. The analysis of the broken bits of rocks can beused to lead students to think about the structure or make-up of those bits. This type of analysis is one way we use science to interpret our environment.
Partially fill one container with water, and a similar container with vinegar. Into each, put a few small (1 cm - 2 cm) pieces of limestone. Look for any evidence of immediate change. Compare the two every 5 minutes for about half an hour. Cover the containers loosely with an aluminum foil cap to prevent excess evaporation, while allowing gas to escape. Continue to observe them once or twice a day for the next week or two.
Explain that vinegar belongs to a class of substances called acids. It is about 1 part acetic acid diluted with 20 parts of water. There are natural acids from decaying plant material and from carbon dioxide dissolved in water which may affect the rocks more than water alone would.
After these observations are complete, remove the pieces of rock which remain in the containers and let the liquid evaporate. Compare the residue in each container after evaporation. This can be related to the formation of stalactites and stalagmites and similar formations.
Factors: B1, B2, B7, C8, C9, C11, C12, F1, F2, G1
Objectives: 2.2
Assessment Techniques: 3, 5, 8, 9
Common Essential Learnings: Critical and Creative Thinking. Comparing the similarities and differences in the processes occurring in the two trials containers and integrating this information with what was previously known is an evaluative activity.
Fill a 10 cm deep aluminum roasting pan, or a similar pan, to a depth of about 5 cm with sandy soil. Pack the soil down well. Fill another pan to about the same depth with good dark topsoil, packed down. Elevate one end of each pan by placing it on one or two books. Use a watering can or a plant mister set to a coarse spray to apply water to the high side of the tray.Compare the amount of erosion in each pan, the type of material eroded, and the way it is deposited at the bottom of the pan.
Repeat the procedure using a greater slope on the pans.
Use pans containing identical soil. With a pencil or a finger, create cultivator-type contours across the slope of one pan and in the direction of the slope of the other. Repeat the erosion test. Ask students to look for evidence of correct contour cultivation in their community.
Prepare two pans with identical soil. Plant some wheat, oats, or grass in one of the pans. Leave the other with no seeds. When the plants in the first pan are three to four cm high, repeat the procedure.
Experiment with other variables which the students identify, for example: trash cover of straw chopped to 1 cm to 2 cm lengths; terracing; allowing a large block of ice placed at the top of the slope to melt.
Factors: B1, B2, C2, C5, C6, C8, C10, C11, F2, F3, F4
Objectives: 2.4, 2.6
Assessment Techniques: 3, 5, 8, 9
Common Essential Learnings: Critical and Creative Thinking. This activity involves the students in comparing similarities and differences, identifying variables which can be tested experimentally, and in creating a "fair" testing procedure.
Develop an unexposed roll of 100 ASA colour slide film. (End pieces of exposed film can usually be obtained free ofcharge from film developing outlets.) Have the processor return the film in standard mounts. Get five or six samples of soilfrom different locations. Twinning with a class in another area of Saskatchewan would be a way of obtaining a wider range of samples. The samples need only be large enough so that the slide mounts containing the film can be pushed vertically to a depth of 3 cm into the soil. Several slides might be placed in each soil sample.
Put the soil samples with the slides in place in a warm (about 25 °C to 30 °C), humid place. Leave for five to ten days. If several slides are in each sample, remove one slide from each sample over the period of several days. Examine the effect of the soil microorganisms on the emulsion of the slides by viewing them under a microscope or on a screen using a slide projector.
Background information
In the top 15 cm of a half a hectare (approximately one acre) of typical farm soil, the following would be found:

1 - 2 tonnes of fungi

1 - 2 tonnes of bacteria

90 kg of protozoa

45 kg of algae

45 kg of yeast

In this activity, the microorganisms in the soil "eat" the gelatin on the film leaving an etching. The more activity present in the soil, the more the gelatin will be removed.The degree of organic activity in the soil is indicative of the health of the soil.
Credit: Dr. D. R. Cullimore, University ofRegina
Factors: B1, B2, C6, C9, C12, E4, F3, F4, G1
Objectives: 2.2, 2.3, 2.4, 2.5
Assessment Techniques: 3, 4, 5, 8, 9
Common Essential Learnings: Critical and Creative Thinking. This gives students data which are unique for every trial, and provides opportunities to look for similarities and differences, to make generalizations, to propose tests of those generalizations.
Make three-dimensional models of the area in which your school is located. The scale of these models can range from describing part of the school yard to many square kilometres. Contours can be formed by covering crumpled paper with papier mâché strips or with paper towels which have been soaked in a plaster of Paris mixture the consistency of soup. These should be smoothed out to dry with as few wrinkles as possible. The final contours can be obtained by spreading a thin layer of plaster of Paris over the model. Finely crushed rock, small pebbles, or soil can be sprinkled on the wet plaster of Paris to depict rocks or bare soil. Alternatively, or with the soil and rock, the model can be painted with tempera paints.
Factors: B1, C4, C5, C12, E4, G1
Objectives: 2.1
Assessment Techniques: 3, 4, 5, 9
Common Essential Learnings: Technological Literacy. Discuss the use of models when large scale projects such as housing developments or highways are being planned. Students during the course of this activity are exploring the relationships between the natural and constructed worlds.
Have students stand close to the surface of a large inflatable sphere, 3 m to 6 m in diameter, such as a weather balloon. Place a piece of tape on the surface of the sphere. The students can change their positions by moving along the circumference of the balloon to discover when they can no longer see the marker. Ask them to place one eye very close to the surface of the sphere and look towards the edge. The edge that they see is like the Earth's horizon.
Weather balloons are available from science supply centres.
Factors: C8, C9, E4, F2
Objectives: 1.1
Assessment Techniques: 1, 3, 7c, 8
Common Essential Learnings: Critical and Creative Thinking. Students compare the disappearance of the object on the surface of the sphere as they move to the appearance or disappearance of grain elevators as one moves toward or away from them. Other than the Earth's curvature, what are some of the factors which are involved here?
Get samples of soil from four or five different locations, ensuring that the soils are quite distinct. Examine the soil samples with hand magnifiers. Each student group could be responsible for examining and describing one sample and explaining the findings to the rest of the class, or each group could have a chance to compare all the samples.
Half fill a jar with water, add about one-quarter of a jar of a soil sample, cap the bottle, and shake. Observe the layers of soil in the bottom of the jar, and the material floating on top of the water. Repeat this procedure for the other soil samples.
Compare the soil layers and the floating material in each jar.
Factors: C2, C4, F3, F4
Objectives: 2.2, 2.3
Assessment Techniques: 1, 3, 5, 8, 9
Common Essential Learnings: Critical and Creative Thinking. Students make careful observations and discuss those observations with each other.
Have students list the foods they ate the previous day. Have them identify those foods which depend on the soil for their origin.
Relate this activity to the Core Unit on Animals.
Factors: A2, B2, C1, C4, C6, F6
Objectives: 2.5, 2.6
Assessment Techniques: 1, 5, 7c
Common Essential Learnings: Critical and Creative Thinking. Reflect on the fact that the existence of human life depends on soil.

Grade 3 Science Core Unit: Earth