Ch 7 - Networks and nanomaterials

Question 1

What is an allotrope?

Answer 1

Each of two or more different physical forms in which an element can exist. Graphite, charcoal, and diamond are all allotropes of carbon.

Question 2

Why are Covalent network lattices giant molecules?

Answer 2

No individual molecules exist, it is simply countless atoms covalently bonded. forming a 3d network lattice

Question 3

What is the mohs scale?

Answer 3

A scale of hardness used in classifying minerals. It runs from 1 to 10 using a series of reference minerals, and position on the scale depends on ability to scratch minerals rated lower.

eg: Diamond has a hardness of 10 so can scratch all things below a 10.

Question 4

What is an example excluding diamond that is a covalent network lattice?

Answer 4

Silicon dioxide, eg sand

Question 5

Properties of Covalent Network Lattices, short explanation of why

Answer 5

VERY hard- strong covalent bonding exists through crystal structureHigh b and m point- Strong covalent bonding holds it togetherDo not conduct heat or electricity- No free ions or electronsBRITLLE- When covalent bonds break, the crystal is distorted and it shattersChemically Inert- No outer shell electrons to reactInsoluble in water and most other solvents

Question 6

what are covalent layer lattices?

Answer 6

Countless atoms held covalently together in planesLayers held together with weak dispersion forces

Question 7

What is graphite?

Answer 7

• Graphite is one of two naturally occurring crystalline forms of the sixth element, carbon, the other being diamond.
• It is an allotrope of carbon
• It is a covalent layer lattice,
• It is a soft greyish black mineral with a metallic lustre.
• A graphite crystal is made up of loosely stacked one atom thick graphene layers much like a deck of cards.

Question 8

Whats a buckyball?

Answer 8

• Buckyballs are composed of carbon atoms linked to three other carbon atoms by covalent bonds. However, the carbon atoms are connected in the same pattern of hexagons and pentagons you find on a soccer ball, giving a buckyball the spherical structure as shown in the attached figure.
• a hollow spherical molecule composed of a large number of carbon atoms.
• “the active layer is made of buckyballs, carbon molecules that are just 1 nanometer in diameter”
• The most common buckyball contains 60 carbon atoms and is sometimes called C60.Other sizes of buckyballs range from those containing 20 carbon atoms to those containing more than 100 carbon atoms.

Question 9

Properties of buckyballs

Answer 9

• Solid at room temp
• Soft and resistant to collision
• Low melting point
• The covalent bonds between carbon atoms make buckyballs very strong, and the carbon atoms readily form covalent bonds with a variety of other atoms. Buckyballs are used in composites to strengthen material.
• Buckyballs have the interesting electrical property of being very good electron acceptors

Question 10

What is Insoluble in water but soluble in methyl benzene?

Answer 10

Buckyballs

Question 11

What are the conduction properties of buckyballs?

Answer 11

Insulator, super conductor, conductor

Question 12

What are nano tubes?

Answer 12

Flat sheets of carbon wrapped up , similir to graphite in a cylinderUses include a space elevator and water filtration

Question 13

What is graphene?

Answer 13

Flat layer of carbon, one atom thick, with remarkable properties. Extremely strong, best conductor there is for heat AND electricity and also more strong and light and flexible than steel

Question 14

What is a covalent molecular substance?describe regular properties.

Answer 14

Substance of covalent molecules held together with weal dispersion, and dipole dipole/hydrogen bondingLow b p and soft

Question 15

Are covalent layer lattices hard or soft?

Answer 15

soft