Glass is an amorphous (non-crystalline) solid, sometimes called a supercooled liquid. It lacks long-range periodic order; atoms are arranged in a disordered network. It softens over a temperature range rather than having a sharp melting point. Common glass is soda-lime-silicate glass. Crystalline solids have sharp melting points and regular lattice structures (e.g., NaCl, quartz).
Explanation:
Calcium (Ca) has a valency of +2, and the phosphate ion (PO₄) has a valency of -3. To balance the charges, we need three calcium ions and two phosphate ions, giving the formula Ca₃(PO₄)₂. This is determined by criss-crossing the valencies of the constituent ions.
Explanation:
Turmeric contains curcumin, a natural indicator that is yellow in acidic/neutral and turns reddish-brown in basic medium. Soap solution is basic (pH ~9-10), thus the stain changes color. This is used as a test for basicity. Vinegar or lemon juice (acid) can reverse the color. Soap is alkaline due to hydrolysis.
Explanation:
Atomic number 8 is oxygen (2,6). It needs 2 more electrons to complete octet, so it gains 2 or shares 2 electrons. Its valency is 2 (typically). It can form two covalent bonds. In H₂O, oxygen forms two bonds.
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