Water - class 8 science revision notes

• Hard and soft water.
  • Advantages of hard water.
  • Disadvantages of hard water.
  • Advantages of soft water.
  • Disadvantages of soft water.
  • Types of water hardness.

Hard and soft water.

Hard water is water which contains dissolved salts ie magnesium and calcium. Mainly from sea,
oceans, boreholes, lakes and dams.

Soft water is water with no or little dissolved salt in it. Mainly rain water.

Advantages of hard water.

• Contains dissolved minerals which are good for our health.
• It has a good taste to drink.
• It is good in brewing industry.

Disadvantages of hard water.

• Wastes a lot of soap because it does not lather easily.
• It discolours teeth when drank.
• It stains clothes.
• It causes clogging and blocking of pipes.
• It forms scales or fur on boilers and hot water pipes.
• Wastes a lot of time and energy during laundry.

Advantages of soft water.

• Does not stains teeth.
• Best in laundry.

Disadvantages of soft water.

• Does not have a good taste.
• Has no minerals required by the body.

Types of water hardness.

There are two types of water hardness, namely;

• Temporary water hardness.
• Permanent water hardness.

Temporary water hardness can be removed by boiling or distillation. Permanent water hardness can be removed by adding chemicals.

NB: The process of removing the dissolved minerals from hard water is called softening.