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