1. Chapter 15 SEction 9 How is Water Purified?
Objectives:
Explain why water must be purified.
Identify five ways to purify water.

2. Drinking Water
Drinking water comes mostly from reservoirs, springs, or wells.
A reservoir is a lake made by people.
Reservoirs store large amounts of fresh water.
Pipelines carry the water to homes and businesses

3. Drinking Water
Some water contains dissolved minerals such as calcium and magnesium.
Water that has high levels of calcium and magnesium in it is called hard water.
It is difficult for soap to form suds in hard water.
Water with few or no minerals in it is called soft water.

4. IDENTIFY:
What are two minerals in hard water?

5. Purifying Water
Water for drinking and bathing must be purified, or cleaned.
Water is usually purified in water treatment plants.

6. Purifying Water Water can be purified in the following ways:
Sedimentation:
The water is allowed to stand for long periods of time.
Heavy particles, such as sand and dirt, settle to the bottom and are removed.

7. Purifying Water Coagulation:
Alum and other chemicals that cause particles to clump together are added to the water.
The clumps of particles settle to the bottom.
The particles settle are then removed from the water.

8. Purifying Water Filtration:
Water is passed through a filter to remove small particles.
Aeration:
Water is sprayed into the air
Oxygen from the air dissolves in the water.
The oxygen kills some of the harmful microorganisms in the water.

9. Purifying Water Chlorination: Chlorine is added to the water.
This chemical kills any harmful microorganisms that are in the water.

10. 2. NAME:
What are five ways to purify drinking water?

11. Desalination
The process of getting fresh water from salt water is called desalination.
One method to desalination is to distill the salt water.
The water is boiled until it evaporates.
This leaves the salt behind.
The water vapor is then condensed to produce liquid fresh water.

12. Desalination Another method involves freezing the water.
This also leaves the salt behind.
A third method is to pump ocean water at high pressure through a fine filter.
The filter separates out much of the salt in the water.
Water still containing too much salt is returned to the ocean.

13. Desalination Desalination is a very costly operation.
It uses large amounts of energy and a lot of equipment.
However, some nations, such as those in the Middle East, do it anyway.
These nations have very limited freshwater resources.

14. 3. DESCRIBE:
What are three ways to desalinate water?

15. 15-9 Classwork CHECKING CONCEPTS
Hard water contains high levels of calcium and ___.
A human-made lake that stores fresh water is called a ___.
Desalination means to ___ salt from water.

16. 15-9 Classwork
4. ANALYZE: Explain the water purification method described in each statement.
Chemicals that cause particles to clump together are added to water.
Water is sprayed into the air.
Water stands for long periods of time.