Unit 4 : Mixing Substances
In this unit, you will learn 

• that different substance have different properties.
• that some substances are unsafe and should be handle with care.
• that a mixture of substances can be separated.

4.1  Different Substances Have Different Properties

    

   

   

     

        

Some substances dissolve in water.  We say the substances are soluble in water.  For example, sugar and salt are soluble in water.

Substances that do not dissolve in water are said to be insoluble.  For example, wheat flour and tapioca flour are insoluble in water.

Some substances, for example, baking powder, gives off a gas when mixed with vinegar.  

4.2  Handling unsafe Substances

     

          

             

4.3  Separating Mixtures

     

    
           

          

                  


                  

Exercise 4.1

1.  Which of the following substances is soluble in water?

a.  milk powder   b.  tapioca flour   c.  sugar    d.  salt    e.  wheat flour

2.  Which of the following substances gives off a gas when mixed with 
     vinegar?

a.  milk powder   b.  sugar   c.  salt   d.  baking powder


Exercise 4.2

Circle the meaning of each hazard warning symbol shown below.  Then circle the correct example of substances of such nature.

             

Exercise 4.3

1. Which of the following mixtures can be separated by filtration?

a. Sand and sugar solution   b. Water and salt   c. Cooking oil and water

2.  which of the following mixtures can be separated by a magnet?

a. Salt and water    b. Iron nail and sand    c. Paper clips and salt

3.  Which of the following mixtures can be separated by using float and sink   
     method?

a. sugar and groundnuts   b. milk powder and nails  c. marbles and corks 

 

UNIT 3 : SOIL

In this unit, you will learn

• what soil is made up of
• the flow of water through different types of soil
• that certain soils are more suitable for plant growth 

3.1 What is soil made up of ?

Soil is very important to us because it supports plants.  Many small animals live in the soil.  Let us find out what soil is made up of.  Soil is made up of humus, clay, silt, sand and small stones.  Humus is the layer on top of the soil surface.  It is black.  It is formed by decaying dead animals and plants.

                  

                                                       


 
3.2 The flow of water through different types of soil

There are three main types of soils.  These three types of soils are different in terms of the size of the soil particles.  They are sand, garden soil and clay.  Sandy soil are yellowish in colour. It contains a lot of air space and are grainy texture.  Garden soil are brown or balck in colour. It contains some air space and are soft and moist texture. Clay soil are red, brown or grey in colour.  It contains very little air space and are smooth and fine texture.

                      


The size of the soil particles affects the flow of water through the different types of soil.  Water moved through sand most easily, followed by garden soil.  Water can hardly  move through clay.  Water moves the fastest through sand and the slowest through clay.  Garden soil is able to keep the right amount of water for the use of plants. 

3.3 Which type of soil is more suitable for plant growth ?

Most plants grow better in garden soil.  This is because garden soil has more humus which make the soil fertile.  Garden soil is also able to keep the right amount of water for the use of plants. 

Exercise 3.1

2.  Why is soil import?

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3.  Why can animals and palnts live in soil?

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4.  What is humus?

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5.  A pupil shakes a mixture of water and some gaarden soil in a tall container. 
     Label the layers that form when the mixture has settled.

 

6.  What is the difference between clay and garden soil?

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7.  What is the difference between sand and garden soil?

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Exercise 3.2

A group of pupils carries out an experiment to test which type od soil is more suitable for plant growth.  The results of their experiment are as shown in Figure 1.

(a)  Which of the soils labelled X, Y and z is garden soil?

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(b)  Why is garden soil more suitable for plant growth?

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(c)  What quantities must be kept constant in the experiment?

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(d)  What quantity is changed in the experiment?

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(e)  What quantity is measured in the experiment?

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(f)  What conclusion can you make from the results of the experiment?

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Unit 2 : External Features of Plants

In this unit, you will learn:

• to identify the external features of plants
• to group plants according to their external features
• to group plants in various ways

2.1 External Features of Plants

Plants have differents sizes, shapes and colours. They make our world a beautiful place to stay in.  Most plants have the same main parts: leaves, stems, flowers and fruits. However, these features do not look the same.

     Most plants heve green leaves.  However, some have yellow or red leaves.  Some leaves are shiny and some are dull.  the surface of leaves are smooth or rough.  The shape of leaves can be irregular, oval, round or long.

Most plants have these features: leaves, stem or flowers.  These features may look similar  or different.  Plants can be grouped according to their similar external features.

Unit 1 : External Features of Animals

In this unit, you will learn:

• to identify the external features of animals
• to group animals according to their external features
• to group animals in various ways

1.1 External Features of Animals

Different animals have different external features. The external features of an animal are the body parts of the animal that you can observe. You can make a list of the external features of each animals.