Books:

• SCIENCE TEXTBOOK FOR CLASS X - Published by National Council of Educational Research and Training 
• Manual of Secondary Science Kit for Classes IX and X -  Published by NCERT

  Websites:

• http://en.wikipedia.org/wiki/Hard_water
• http://chemistry.about.com/cs/howthingswork/a/aa082403a.htm
• http://en.wikipedia.org/wiki/Soap
• http://www.elmhurst.edu/~chm/vchembook/554soap.html
• http://www.cleaninginstitute.org/clean_living/soaps__detergents_products__ingredients.aspx