How woolen clothes help us in winter against cold?

Raju noticed that while washing clothes by using rain water collected in a tank, the quantity of soap required was found to be less than that required using tap water. a. If Raju asked the reason behind it, how will you explain it? b. Also mention any two methods to overcome.it,

In olden days people were using washing soda for washing clothes. Can washing soda be useful to clean clothes in all types of water? Justify your answer.

While washing clothes by using rain water collected in a tank, the quantity of soap required was found to be less than that required using tap water. What may be the reason?

How do the oral pills help in birth control?