[https://dsert.kar.nic.in/kalikachetarike/7thEngScienceLS.pdf Kalika chetharike Material], [https://www.youtube.com/watch?v=eUejqjWC8Ws&list=PLj2EUkWt-rYYrW4F_jtKRCvjiu3i0OYL9&index=2 Litmus Paper test to detect Acid, Bases and Neutral substance]
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[https://dsert.kar.nic.in/kalikachetarike/7thEngScienceLS.pdf Kalika chetharike Material], [https://www.youtube.com/watch?v=eUejqjWC8Ws&list=PLj2EUkWt-rYYrW4F_jtKRCvjiu3i0OYL9&index=2 Litmus Paper test to detect Acid, Bases and Neutral substance]