Lesson 3.4 Purifying Water

The water you drink has been processed so that it is safe to drink. How is the water from a river or a lake turned into safe drinking water?

Read page 54 to learn how municipalities purify water.

Question 1. List the four steps used in purifying water described on page 54.

Question 2. Another step in purifying water that is not one of the steps discussed on page 54 was mentioned on page 50. What step was this? Is it an important step?

Then, return here to continue this lesson.

 

 

Another way of purifying water involves fewer steps and chemicals.

Read the paragraph on distillation at the top of page 55.

Question 3. Explain what is meant by distillation.

Question 4. Why is distillation not used to purify all drinking water?

Then, return here to continue this lesson.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. List the four steps used in purifying water described on page 54.

Step 1: Alum is added to the water. The dirt particles stick to the alum.
Step 2: These large particles of dirt and alum sink to the bottom where they are separated from the water.
Step 3: Filters remove any remaining particles that would not sink to the bottom.
Step 4: Chemicals such as chlorine are added to kill any bacteria.

Question 2. Another step in purifying water that is not one of the steps discussed on page 54 was mentioned on page 50. What step was this? Is it an important step?

The step discussed on page 50 was that substances are added to remove dissolved chemicals. You may be familiar with some of these dissolved chemicals such as iron and calcium.

 

Click to return to where you left off in this lesson.

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 3. Explain what is meant by distillation.

Distillation is the process of separating a substance from a solution by evaporating the substance, collecting the vapour, and then condensing the vapour into liquid again.

Question 4. Why is distillation not used to purify all drinking water?

Distillation required a tremendous quantity of energy and is very expensive compared to the method described on page 54.


Now, do Assignment 3C. Page forward to access the computer-scored assignment.