Understanding Water Hardness

The video explains the concept of water hardness, distinguishing between soft and hard water. Soft water, like rainwater, is free of dissolved salts, while hard water contains calcium ions from rocks. Temporary hardness, caused by calcium carbonate, can be removed by boiling, but leads to lime scale. Permanent hardness, from calcium sulfate, does not form lime scale but still causes soap scum. Soap reacts with calcium ions to form insoluble scum, while detergents avoid this issue. The video concludes with a summary of these concepts.

What makes rainwater soft compared to well or tap water?

• High pH level

• Presence of magnesium ions

• Absence of dissolved salts

• Presence of calcium ions

Why does rainwater not contain salts?

• Salts are absorbed by plants

• Salts are left behind in the seas

• Salts evaporate with water

• Salts dissolve in the air

What causes temporary hardness in water?

• Calcium sulfate

• Magnesium chloride

• Calcium carbonate

• Sodium chloride

How can temporary hardness be removed?

• Adding salt

• Boiling the water

• Filtering the water

• Adding vinegar

What is the main component of lime scale?

• Sodium bicarbonate

• Magnesium sulfate

• Calcium carbonate

• Calcium sulfate

What is the cause of permanent hardness in water?

• Sodium chloride

• Magnesium bicarbonate

• Calcium sulfate

• Calcium carbonate

Why does soap form scum in hard water?

• Soap reacts with sodium ions

• Soap reacts with potassium ions

• Soap reacts with magnesium ions

• Soap reacts with calcium ions

What makes detergents effective in hard water?

• They contain sodium chloride

• Their calcium salts are soluble

• They contain calcium carbonate

• Their sodium salts are insoluble

What is the main difference between temporary and permanent hardness?

• Temporary hardness can be removed by boiling

• Permanent hardness is caused by calcium carbonate

• Permanent hardness can be removed by boiling

• Temporary hardness is caused by calcium sulfate

What is the effect of hard water on soap usage?

• Soap dissolves completely

• Soap becomes more effective

• Soap forms scum

• Soap lathers easily