8. Table 2 shows the volume of soap solution needed to form lather with three samples of' water of equal volumes. Use the data from the table to answer the questions that follow:

Table 2

(a) Identify two things other than the volume of water that must be kept constant for such data to be meaningful.

(b) Identify which water sample has the highest hardness. Give a reason.

(ii) Give three causes of hardness of water.

Distinguish temporary hardness from permanent hardness of water.

 With the help of chemical equations, explain how you can remove each type of water hardness

Name the compound which causes temporary hardness of water and the compound which causes permanent hardness of water.

Write one balanced chemical equation in each case to show how to remove temporary and permanent hardness of water.

   With the aid of a chemical equation, briefly explain how

1. temporary hardness of water can be removed by boiling.
2. permanent hardness of water can be removed by chemical means.

25cm  ³  samples of water A, B, C and D were tested with soap solution. The volume of soap solution required to produce a lather that lasted for a minute was recorded. Fresh samples of each were boiled and tested again with soap solution. The results are shown in Table 1.

Table 1.

1. Which sample probably contains temporary hardness of water only?

2. Which sample probably contains both permanent and temporary hardness of water? Give a reason for your answer.
   
   

 Table 2 gives some information about the composition of three samples of water from wells in Kahama, Maswa and Bukombe districts.

 Table 2

(i)  State two ways in which these ions get into the samples of water.

(ii)  Giving two reasons, state the hardest sample of water.

(iii)  State two ways that can be used to remove ions in (ii).

Giving four reasons, explain why people who use hard water can expect higher costs than people who use soft water.

 Lack of safe water for domestic and industrial uses is a serious problem in most of Tanzanian towns. The major cause of this problem is pollution in the water sources. Slate three methods that could make water from a pond or a well be safe for drinking.