Natural scienceS

GrADE 5

PLANET Earth AND The UNIVERSE

Module 22

WHAT SOIL CONSISTS OF

Activity 1:

to determine what soil consists of

[LO 1.2; LO 1.3]

What does soil consist of?

Do the following investigation on your own:

Scoop up a handful of garden soil from your garden and place it in a transparent container.

Add water until the container is about three-quarters full.

Seal the container and shake it very well.

Place the container on a windowsill or any other place where you can observe it carefully.

Write down your observations by answering the following questions:

1. How long did it take before the water was relatively clear?

2. Soil forms layers when it settles down. How many layers can you distinguish?

3. The size of the particles in the different layers differs. Which layer looks the coarsest (i.e. has the largest particles)?

4. Which layer appears to be the finest (has the smallest particles)?

5. What is floating on the surface of the water?

6. Does the soil in your friends’ containers look exactly the same as yours? Describe.

ACTIVITY 2: To examine different types of soil and to be able to explain why plants grow best in certain types of soil

[LO 1.2; LO 1.3]

Different types of soil

There are mainly three types of soil: sandy soil, loamy soil and clayey soil.

The soil types differ with regard to their ability to absorb water, to retain water and to let in air.

The following examination will indicate how the three types of soil differ from each other in this regard:

Work in groups of three.

One group member brings clayey soil to school, the other one brings sandy soil and the last one brings loamy soil.

Bring three empty cool drink bottles of the same size. The top half of the bottle must be removed.

Fill each container one-third full of soil. Each container must contain a different kind of soil. Compact the soil.

Place the containers next to each other on a table or on any level surface, and slowly pour 250 ml water into each container.

Note in which one the water is absorbed most rapidly.

Quickly make six little holes of the same size in the bottom of each container and place each container on a glass jug. The glass jugs must be of the same size.

Note into which jug the most water has seeped after a certain time.

Write down your conclusions. Mention all three types of soil.

Make a sketch of your apparatus.

Question: In which type of soil will plants grow best?

Explain:

Activity 3: To examine how topsoil is formed

[LO 2.2]

Study the sketches below and then answer the questions that follow:

weathering rock

1. Why is the top layer depicted as being dark?

2. Why is the dark layer in the right-hand sketch thicker than the one in the sketch in the centre?

3. How do the plants in the right-hand sketch differ from those in the sketch in the centre? You must also explain why they differ.

Let us apply your answers and reach a few important conclusions:

The top layer of soil differs from the deeper soil because it contains more humus (decayed plant material). We speak of topsoil that is fertile.

There is a cycle: plants make the soil more fertile, and fertile soil makes plants grow better.

The thicker the topsoil, the deeper the plant is able to grow to take up nourishment and water from the soil, and the better able are the roots to anchor the plant in the soil so that it does not wash away when it rains.

If there are no plants, or if the plant roots grow very shallowly, the soil will be washed away easily.

Assessment

LO 1: SCIENTIFIC INVESTIGATIONLearners respond confidently to their desire to learn about natural phenomena; they investigate relationships and solve problems within the context of science, technology and the environment.

we know this when the learner:

plans investigations;

1.2 takes the lead in investigating and collecting data;

1.3 evaluates data and communicates findings.

LO 2: CONSTRUCTION OF SCIENTIFIC KNOWLEDGELearners know, interpret and apply scientific, technological and environmental knowledge.

we know this when the learner:

2.2 recalls significant information;

2.3 categorises information

Memorandum

Activity 1

This simple experiment is certainly worth doing.

Answers:

from learners' own observations

Question 5: dead plant material

Activity 2

Ensure that the learners all use the same size container. Learners have to answer the questions themselves according to their own observations. Plants grow best in loamy soil, because the soil is loose enough for the roots to grow in , water, organic material and oxygen can penetrate the soil, but the water does not run through immediately. Therefore the nutrients do not wash away and the soil stays moist. The plant is better anchored than in sand.

Activity 3

It contains organic material (especially plant remains)

Plants have grown in it for a longer time

Larger, deeper-reaching roots. Can anchor better and absorb more nutrients and water.

Content actions

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Last edited by Siyavula Uploaders on Jul 16, 2009 5:06 am -0500.