Natural rubber (cis-1,4-polyisoprene) is an addition polymer of isoprene (2-methyl-1,3-butadiene). It is obtained from latex of rubber tree (Hevea brasiliensis). It is elastic but weak. Vulcanization with sulfur introduces cross-links, improving strength and elasticity. Ethene gives polyethylene; styrene gives polystyrene; vinyl chloride gives PVC.
Explanation:
Teflon (PTFE) has a very low coefficient of friction and surface energy because the fluorine atoms form a protective shield around the carbon backbone, making it difficult for other substances to adhere. This is not due to polarity (C-F bonds are polar but the molecule overall is non-polar due to symmetry). It is extremely inert, resisting most chemicals.
Explanation:
The salt bridge (e.g., KCl-agar) allows migration of ions between half-cells, completing the circuit and maintaining charge neutrality. Without it, charge buildup would stop the reaction. It does not increase current or electrode potential. It prevents mixing of solutions. A porous membrane can also serve. Ions in the bridge must have similar mobility and not interfere with cell reactions.
Explanation:
Diamond is the hardest known natural substance. It consists of each carbon atom covalently bonded to four other carbon atoms in a rigid tetrahedral 3D lattice, making it extremely hard. Graphite is soft due to its layered structure with weak van der Waals forces between layers.
No comments yet. Be the first to start the discussion!