Bonding, Structure and the Properties of Matter

Question 1

What is ionic bonding?

Answer 1

Ionic bonding is the electrostatic attraction between positive and negative ions. It is a relatively strong attraction

Question 2

How are ionic compounds held together?

Answer 2

They are held together in a giant lattice
It’s a regular structure that extends in all directions in a substance
Electrostatic attraction between positive and negative ions holds the structure together

Question 3

State properties of ionic substances (3 points)

Answer 3

• High melting and boiling point (strong electrostatic forces between oppositely charged ions)
• Do not conduct electricity when solid (ions in fixed positions)
• Conduct when molten or dissolved in water- ions are free to move

Question 4

How are ionic compounds formed? (4 points)

Answer 4

• Reaction of a metal with a non-metal
• Electron transfer occurs - metal gives away its outer shell electrons to non-metal
• Mg is in group 2, so has 2 available outer shell electrons
• O is in group 6, so can accept 2 electrons to get a full outer shell cofiguration

Question 5

What is a covalent bond?

Answer 5

Covalent bond is a shared pair of electrons between two atoms

Question 6

Describe the structure and properties of simple molecular covalent substances (4 points)

Answer 6

• Do not conduct electricity (no ions)
• Small molecules
• Weak intermolecular forces
• Low melting and boiling points

Question 7

How do intermolecular forces change as the mass/size of the molecule increases?

Answer 7

They increase. That causes melting/boiling points to increase as well (more energy needed to overcome these forces)

Question 8

What are polymers?

Answer 8

Polymers are very large molecules with atoms linked by covalent bonds

Question 9

What are thermosoftening polymers?

Answer 9

Special type of polymers, they melt/soften when heated. There are no bonds between polymer chains. Strong intermolecular forces ensure that the structure is solid at room temperature. These forces are overcome with heating - polymer melts

Question 10

What are giant covalent substances? Give examples (4 points)

Answer 10

• Solids, atoms covalently bonded together in a giant lattice
• High melting/boiling points - strong covalent bonds
• Moslty don’t conduct electricity (no delocalised e-)
• Diamond, graphite, silicon dioxide

Question 11

Describe and explain the properties of diamond (4 points)

Answer 11

• Four, strong covalent bonds for each carbon atom
• Very hard (strong bonds)
• Very high melting point (strong bonds)
• Does not conduct (no delocalised electrons)

Question 12

Describe and explain the properties of graphite (5 points)

Answer 12

• Three covalent bonds for each carbon atom
• Layers of hexagonal rings
• High melting point
• Layers are free to slide as weak intermolecular forces between layers: soft, can be used as a lubricant
• Conduct thermal and electricity due to one delocalised electron per each carbon atom

Question 13

Describe and explain the properties of fullerines (3 points)

Answer 13

• Hollow shaped molecules
• Based on hexagonal rings but may have 5/7 -carbon rings
• C60 has spherical shape, simple molecular structure (buckminsterfullerene)

Question 14

Describe and explain the properties of nanotubes (3 points)

Answer 14

• Cylindrical fullerene with high length to diameter ratio
• High tensile strength (strong bonds)
• Conductivity (delocalised electrons)

Question 15

Describe and explain the properties of graphene (1 point)

Answer 15

A single layer of graphite

Question 16

What is metallic bonding?

Answer 16

Forces of attraction between delocalised electrons and nuclei of metal ions

Question 17

Describe properties of metals

Answer 17

• High melting/boiling points (strong forces of attraction)
• Good conductors of heat and electricity (delocalised electrons)
• Malleable, soft (layers of atoms can slide over each other whilst maintaining the attraction forces)

Question 18

What are alloys?

Answer 18

• Mixtures of metal with other elements, usually metals
• Different sizes of atoms distorts the layers, so they can’t slide over each other, therefore alloys are harder than pure metals

Question 19

What are the limitations of the simple model?

Answer 19

There are no forces between spheres and atoms, molecules and ions are solid spheres - this is not true

Question 20

What does the amount of energy needed to change state from solid to liquid or liquid to gas depend on?

Answer 20

The strength of the forces between the particles of the substance. The nature of the particles involved depends on the type of bonding and the structure of the substance. The stronger the forces between the particles the higher the melting point and boiling point of the substance

Question 21

A pure substance will melt or boil at…? What about a mixture?

Answer 21

A fixed temperature
A mixture will melt over a range of temperatures

Question 22

What are the three states of matter?

Answer 22

Solid, liquid and gas

Question 23

What is nanoscience?

Answer 23

Science that studies particles that are 1 - 100nm in size

Question 24

State the used of nanoparticles (4 points)

Answer 24

• Medicine (drug delivery systems)
• Electronics
• Deodorants
• Sun creams (better skin coverage and more effective protection against cell damage)

Question 25

What are fine and coarse particles?

Answer 25

• Fine particles (soot), 100-2500nm diameter
• Coarse particles (dust), 2500-10(5)nm diameter

Question 26

Why do nanoparticles have properties different from those for the same materials in bulk?

Answer 26

High surface area to volume ratio