C2.2 structure and propertes

Question 1

explain eatures of simple molecular subs . etc.Cl2, O2,H20

Answer 1

===SIMPLE MOLECULAR SUBSTANCES are gases, liquids or solids that have
relatively low melting points and boiling points.they have these features because there are have only weak forces between the molecules (intermolecular forces). this means that they can be easily parted.
===c) Substances that consist of simple molecules do not conduct electricity because the molecules do not have an overall electric charge

Question 2

explain the features of ionic compounds such as sodium chloride

Answer 2

Ionic compounds have regular structures (giant ionic lattices) in which there are strong
electrostatic forces in all directions between oppositely charged ions. These compounds
have high melting points and high boiling points because of the large amounts of energy needed to break the many strong bonds.
b) When melted or dissolved in water, ionic compounds conduct electricity because the ionsare free to move and carry the current.

Question 3

what is oxidation and reduction

Answer 3

oxidation is loss + cation

reduction is gain - anion

Question 4

give examples of giant covalent structures

Answer 4

Atoms that share electrons can also form giant structures or macromolecules. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures (lattices) of atoms. All the atoms in these structures are linked to other atoms by strong covalent bonds and so they have very high melting points.

Question 5

why is diamond very hard

Answer 5

In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a
giant covalent structure, so diamond is very hard.

Question 6

graphite

Answer 6

In graphite, each carbon atom bonds to three others, forming layers. The layers are free to slide over each other because there are no covalent bonds between the layers and so graphite is soft and slippery.it is also soft because there are weak intermolecular forces between them.
In graphite, one electron from each carbon atom is delocalised. These delocalised
electrons allow graphite to conduct heat and electricity. (HT only)You should realise that graphite is similar to metals in that it has delocalised

Question 7

FULLERENE

Answer 7

FULLERENE – carbon atoms joined together to make large cages.Fullerenes can
be used for drug delivery into the body, in lubricants, as catalysts, and in nanotubes for
reinforcing materials, e.g. in tennis rackets. (

Question 8

Metallic bonding

Answer 8

Metallic bonding is formed as a lattice of metal atoms (or positively charged ions) arranged in regular layers. The outer electrons easily move from one atom to the next so we say they form a ‘sea’ of free electrons surrounding positively charged metal ion.

Question 9

thermal conductivity ..metals

Answer 9

metals are better conductors because they have free electrons .Heat energy is passed up by the electrons as additional kinetic energy.As particles collide they pass on the kinetic energy.Metals conduct heat and electricity because of the delocalised electrons in their
structures. (HT only)
You should know that conduction depends on the ability of electrons to move
throughout the metal. (HT only)

Question 10

high melting and boiling point..metals 0

Answer 10

Strong electrostatic forces of attraction between the negative elecrons and positive metal ions bond the metal ions together.this strong force of attraction is dificult to break when heated

Question 11

malleability..metal

Answer 11

The delocalised electrons allow metal ions to slide past each other,

Question 12

Alloys

Answer 12

Alloys – a mixture of metals or a metal and a non-metal: steels is a mixture of iron and different percentages of carbon; brass is a mixture of copper and zinc; shape memory alloys have a special property.

Question 13

what is nanotechnology and examples

Answer 13

The application of nanoparticles for particular uses.Sensors; Highly efficient catalyst coatings on construction materials; More effective drugs..

Question 14

properties of polymers

Answer 14

• –low density
• –good corrosion resistance
• –can be produced transparent and in a ny colour

Question 15

what is cross linking

Answer 15

it is where the polymer cghains are chemicallly joined together .this prevents them from sliding past each other .trhis makes the material tougher and less felxible
Thermosetting polymers consist of polymer chains with cross-links between them so that they do not melt when they are heated.-

Question 16

Thermosoftening polymers

Answer 16

Thermosoftening polymers consist of individual, tangled polymer chains. they get softer when heated because there are no cross links between th molecules.
These plastics are flexible and melt when heated because there are weak intermolecular forces
between the polymer chains so they can slide over each other easily.

Question 17

Thermosetting

Answer 17

Thermosetting ==These plastic are rigid and
do not melt when heated because there are strong
intermolecular forces (cross links)between the polymer
chains

Question 18

Graphite use

Answer 18

Graphite
Graphite is soft and slippery because there are only weak intermolecular forces between its layers.

Graphite is a good conductor of heat aitnd electricity. This is because, like metals, graphite contains delocalised electrons. These electrons are free to move through the structure of the graphite.

Question 19

nanometres

Answer 19

A nanometre (nm), is one billionth of a metre (or a millionth of a millimetre). Nanoparticles range in size from about 100nm down to about 1nm.
Nanoparticles have a very large surface area compared wit heir volume, so they are often able to react very quickly. They can, for example, be used in self-cleaning ovens and
windows.