How Structure Influnece The Properties And Uses Of A Substance

Question 1

What can’t substances with simple molecules do and why?

Answer 1

They cannot conduct electricity because the molecules do not have an overall charge

Question 2

Describe the structure of an ionic compound.

Answer 2

Ionic compounds have regular structures (giant ionic lattices) in which there are strange electrostatic forces in all directions between oppositely charged ions. These compounds have high melting and boiling points because of the large amount of energy need to break the many bonds

Question 3

What happens when ionic compounds are melted or dissolved in water?

Answer 3

They conduct electricity because the ions are free to move and carry a current

Question 4

What can atoms that share electrons form?

Answer 4

Giant structures or macromolecules

Question 5

Describe the structure of a macromolecule.

Answer 5

All the atoms in these structures are linked to another atom by stronger covalent bonds and so they have very high melting points

Question 6

Describe the structure of a diamond

Answer 6

In dimond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, making diamond very hard

Question 7

Describe the structure of graphite.

Answer 7

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.
In graphite, one electron form each carbon atom is delocalised. These delocalised electrons allow graphite to conduct heat and energy

Question 8

Give example of macromolecules.

Answer 8

Diamond and graphite (forms of carbon) and silicon dioxide (silica)

Question 9

What is fullerenes, and what can it be used for?

Answer 9

It is another form of carbon, with different numbers of carbon atoms. Fullerenes can be used for drip delivery into the body, in lubricants, catalysts, and in nanotubes for reinforcing materials e.g in tennis rackets

Question 10

What is the structure of fullerenes?

Answer 10

It is based on hexagonal rigs of carbon atoms

Question 11

Why can metals conduct heat and electricity?

Answer 11

Because of the delocalised electrons in their structure

Question 12

What allows metals to bend and be shaped?

Answer 12

The layers of atoms in the metal are able to slide over each other

Question 13

Describe the structure of alloys.

Answer 13

Alloys are usually made from two or more different metals. The difference sized atoms of the metals distort the layers in the structure, making it more difficult for them to slide over each other and so make alloys header than pure metals

Question 14

What can shape memory alloys do?

Answer 14

They can return to their original shape after being deformed

Question 15

Give an example of a shape memory alloy

Answer 15

Nitinol, used in dental braces

Question 16

What do the properties of polymers depend on?

Answer 16

It depends on what they are made from and the conditions under which they are made. E.g., low density and high density poly(ethene) are produced using different catalysts and reaction conditions

Question 17

What do thermosoftening polymers consist of?

Answer 17

They consist of individual tangled polymer chains. They consist of polymer chains with cross-links between them so that they do not melt when they are heated

Question 18

What does nanoscience refer to?

Answer 18

To sutrcutures that are 1-100 nm in size, of the order of a few hundred atoms

Question 19

What do nanoparticles show and what can they possibly be used for?

Answer 19

They show different properties to the same materials in bulk and have a high surface area to volume ratio, which may lead to the development of new computers, new catalysts, new coatings, highly sedative sensors, and new cosmetics such as sun tan creams and deodorants.

Question 20

What does it mean if a substance consist of simple molecules?

Answer 20

These are gases, solids or liquids which have relatively low meting and boiling points. This is because they only have weak intermolecular forces). It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils