Is sand a covalent crystalline substance?

Answer 1

Covalent

The structure of silicon dioxide, SiO2

Silicon dioxide is also known as silicon(IV) oxide.

The giant covalent structure of silicon dioxide

There are three different crystal forms of silicon dioxide. The easiest one to remember and draw is based on the diamond structure.

Crystalline silicon has the same structure as diamond. To turn it into silicon dioxide, all you need to do is to modify the silicon structure by including some oxygen atoms.

Notice that each silicon atom is bridged to its neighbours by an oxygen atom. Don't forget that this is just a tiny part of a giant structure extending on all 3 dimensions.

Note: If you want to be fussy, the Si-O-Si bond angles are wrong in this diagram. In reality the "bridge" from one silicon atom to its neighbour isn't in a straight line, but via a "V" shape (similar to the shape around the oxygen atom in a water molecule). It's extremely difficult to draw that convincingly and tidily in a diagram involving this number of atoms. The simplification is perfectly acceptable.

The physical properties of silicon dioxide

Silicon dioxide

• has a high melting point - varying depending on what the particular structure is (remember that the structure given is only one of three possible structures), but around 1700°C. Very strong silicon-oxygen covalent bonds have to be broken throughout the structure before melting occurs.

• is hard. This is due to the need to break the very strong covalent bonds.

• doesn't conduct electricity. There aren't any delocalised electrons. All the electrons are held tightly between the atoms, and aren't free to move.

• is insoluble in water and organic solvents. There are no possible attractions which could occur between solvent molecules and the silicon or oxygen atoms which could overcome the covalent bonds in the giant structure.

http://www.chemguide.co.UK/atoms/structures/giantcov.HTML

veryy helpfull for chemistryy =D

Answer 2

Sand is usually a mixture, having been formed from the break up of different rocks. Most sand has silica, (silicon dioxide) as its principle component, and this is a covalent macromolecule. (There are two types of crystal formed by covalent substances, molecular and macromolecular).

Answer 3

Sand is principally silica, SiO2 which is covalent compound, a giant molecule

Answer 4

If the sand is formed from silicon dioxide bonds are covalent.If the sand is formed from calcium carbonate bonds are ionic.etc.

Answer 5

covalent network i think.