Do as instructed:[2 M]

Questions

3 questions · self-marked practice — reveal the answer and mark yourself.

Question 12 Marks

Write short notes on or Explain:
Surface activity

Answer

Soap molecule has the property of holding on to both oil and water soap water spreads easily on many types of surfaces.
The property of a substance of spreading on a surface is called surface activity and the substance is said to be a surfactant.
Detergents are surface-active. One effect of surface activity is lather formation.

Question 22 Marks

Write short notes on or Explain:
Concrete

Answer

Concrete is prepared by mixing cement, water, sand and gravel.
For making a strong and leak proof slab certain substances are mixed in concrete.
Now a days, roads are made of concrete because they are very durable, strong and smooth.

Question 32 Marks

Write short notes on or Explain:
Natural detergent

Answer

It is naturally available soap nut (ritha) and soap pod (shikekai) are the natural detergents in common use.
They contain a chemical named saponin.
Soap nut and soap pod do not have any harmful effect on human skin or on silk, woollen threads, and cloth.

Science Do as instructed:[2 M]