सुरक्षा माचिसों की रगड़ने वाली सतह या तीली के शीर्ष पर मुख्य रूप से किस तत्व का उपयोग किया जाता है?

To prevent the oxidation and rancidity of potato chips during storage, manufacturers flush the sealed bags with which gas?

Early matches ignited when struck on a rough surface primarily due to the friction of which substance?