Bonding, Structure, And The Properties Of Matter Flashcards
1
Q
What are Carbon nanotubes?
A
- Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios.
- Their properties make them useful for nanotechnology, electronics and materials.
2
Q
Who discovered the first fullerene?
A
The first fullerene to be discovered was Buckminsterfullerene (C60) which has a spherical shape.
3
Q
What are fullerenes?
A
- Fullerenes are molecules of carbon atoms with hollow shapes.
- The structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms.
4
Q
What is graphene?
A
Graphene is a single layer of graphite and has properties that make it useful in electronics and composites.
5
Q
In graphite, what happens to one electron from each carbon atom?
A
It is delocalised.
6
Q
What is the carbon structure of graphite?
A
In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings which have no covalent bonds between the layers.
7
Q
What are the properties of diamond?
A
- very hard
- very high melting point
- does not conduct electricity
8
Q
What is the carbon structure of diamond?
A
In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard, has a very high melting point and does not conduct electricity.
9
Q
Why are metals good thermal conductors?
A
Metals are good conductors of thermal energy because energy is transferred by the delocalised electrons.
10
Q
Why are metals good conductors of electricity?
A
Metals are good conductors of electricity because the delocalised electrons in the metal carry electrical charge through the metal.
11
Q
What are the properties of pure metals?
A
In pure metals, atoms are arranged in layers, which allows metals to be bent and shaped. Pure metals are too soft for many uses and so are mixed with other metals to make alloys which are harder.
12
Q
What are the properties of metals?
A
Metals have giant structures of atoms with strong metallic bonding. This means that most metals have high melting and boiling points.
13
Q
What are examples of giant covalent structures?
A
Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures.
14
Q
How are the atoms in giant covalent structures linked?
A
All of the atoms in these structures are linked to other atoms by strong covalent bonds.
These bonds must be overcome to melt or boil these substances.
15
Q
What is the melting point of giant covalent structures like?
A
Substances that consist of giant covalent structures are solids with very high melting points.
16
Q
What are the forces between polymer molecules like?
A
The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.
17
Q
What are the forces between polymer molecules like?
A
The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.
18
Q
What are polymers?
A
Polymers have very large molecules. The atoms in the polymer molecules are linked to other atoms by strong covalent bonds.
19
Q
Why do small molecules not conduct electricity?
A
These substances do not conduct electricity because the molecules do not have an overall electric charge.
20
Q
How does the intermolecular force depend on the size of the molecule?
A
The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.
21
Q
What are the forces of small molecules like?
A
These substances have only weak forces between the molecules (intermolecular forces).
It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils.
22
Q
What are the substances that usually consist of small molecules?
A
Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points.
23
Q
What happens when ionic compounds are melted or dissolved in water?
A
When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.
24
Q
What are the substances that usually consist of small molecules?
A
Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points.
25
What happens when ionic compounds are melted or dissolved in water?
When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.
26
What is the boiling point for ionic compounds like?
- high melting points.
- high boiling points.
- because of the large amounts of energy needed to break the many strong bonds.
27
What are the structure of ionic compounds like?
lonic compound have regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions.
28
What does aqueous solution stand for as a chemical equation?
(aq)
29
What are the chemical equations for the three states of matter?
(s), (I) and (g)
30
What are limitations of the particle theory?
Limitations of the particle theory model include that in the model there are no forces, that all particles are represented as spheres and that the spheres are solid
31
How does a stronger force affect the melting and boiling point?
The stronger the forces between the particles the higher the melting point and boiling point of the substance.
32
How do we determine the amount of energy needed to change the state of a substance?
The amount of energy needed to change state from solid to liquid and from liquid to gas depends on 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.
33
When does melting, freezing, boiling and condensing take place?
Melting and freezing take place at the melting point, boiling and condensing take place at the boiling point.
34
What are three states of matter?
- solid
- liquid
- gas
35
In metallic bonding, what do the electrons on the outer shells do?
The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure. The sharing of delocalised electrons gives rise to strong metallic bonds.
36
What do metals consist of?
Metals consist of giant structures of atoms arranged in a regular pattern.
37
What are examples of giant covalent structures?
Some covalently bonded substances have giant covalent structures, such as diamond and silicon dioxide.
38
What do metals consist of?
Metals consist of giant structures of atoms arranged in a regular pattern.
39
What are examples of giant covalent structures?
Some covalently bonded substances have giant covalent structures, such as diamond and silicon dioxide.
40
What sort of molecules are in covalently bonded substances?
Some covalently bonded substances have very large molecules, such as polymers.
41
Do covalently bonded substances consists of just large molecules?
Covalently bonded substances may consist of small molecules.
42
Are covalent bonds strong or weak?
Covalent bonds between atoms are strong.
43
What bond is it called when atoms share atoms with pairs of electrons?
Covalent bonds
44
What is an ionic compound?
An ionic compound is a giant structure of ions. lonic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions. These forces act in all directions in the lattice and this is called ionic bonding.
45
What does the charge of ions produced by metals relate to?
The charge on the ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 relates to the group number of the element in the periodic table.
46
What diagram can be used to show an electron transfer during the formation of an ionic compound?
The electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram, eg for sodium chloride.
47
What structure do ions in group 1,2,6 and 7 produce?
The ions produced by metals in Groups 1 and 2 and by nonmetals in Groups 6 and 7 have the electronic structure of a noble gas (Group 0).
48
What happens when a metal atom reacts with a non-metal atom?
- Metal atom are transferred.
- Metal atoms lose electrons to become positively charged ions.
- Non-metal atoms gain electrons to become negatively charged ions.
49
When does metallic bonding occur?
Metallic bonding occurs in metallic elements and alloys.
50
When does covalent bonding occur?
Covalent bonding occurs in most non-metallic elements and in compounds of non-metals.
51
When does ionic bonding occur?
lonic bonding occurs in compounds formed from metals combined with non-metals.
52
What are the atoms like in metallic bonding?
For metallic bonding the particles are atoms which share delocalised electrons.
53
What are the atoms like for covalent bonding?
For covalent bonding the particles are atoms which share pairs of electrons.
54
What are ions like for ionic bonding?
For ionic bonding the particles are oppositely charged ions.
55
What are the three types of strong chemical bonds?
- ionic
- covalent
- metallic
56
How are ionic compounds held together?
• 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.
57
State properties of ionic substances
• High melting and boiling point (strong electrostatic forces between oppositely charged ions)
Do not conduct electricity when solid (ions in fixed positions).
• Conduct when moten or dissolved in water- ions are free to move.
58
Describe the structure and properties of simple molecular covalent substances
- Do not conduct electricity (no ions)
Small molecules
- Weak intermolecular forces, therefore:
- Low melting and boiling points
59
How do intermolecular forces change as the mass/size of the molecule increases?
They increase. That causes melting/boiling points to increase as well (more energy needed to overcome these forces).
60
What are polymers? What are thermosoftening polymers?
Polymers are very large molecules (>100s, 1000s of atoms) with atoms linked by covalent bonds.
Thermosoftening polymers - 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.
61
What are giant covalent substances? Give examples
- Solids, atoms covalently bonded together in a giant lattice.
- High melting/boiling points - strong covalent bonds.
- Mostly don't conduct electricity (no delocalised e*)
- Diamond, graphite, silicon dioxide.
62
What are alloys? Why are they harder than pure metals?
Alloys:
- 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
63
What are the limitations of the simple model?
There are no forces between spheres and atoms, molecules and ions are solid spheres - this is not true
64
What does the amount of energy needed to change state from solid to liquid or liquid to gas depend on?
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
65
A pure substance will melt or boil at...? What about the mixture?
A fixed temperature.
A mixture will melt over a range of temperatures.
66
What is nanoscience?
Science that studies particles that are 1 - 100m in size
67
State the uses of nanoparticles
- Medicine (drug delivery systems)
- Electronics
- Deodorants
- Sun creams (better skin coverage and more effective protection against cell damage)
68
What are fine and coarse particles?
- Fine particles (soot), 100-2500 m diameter
- Coarse particles (dust), 2500-105 m diameter
69
Why do nanoparticles have different properties to those for the same materials in bulk?
High surface area to volume ratio
70
What are the properties of nanotubes?
Nanotubes
- cylindrical fullerene with high length to diameter ratio
-High tensile strength (strong bonds)
- Conductivity (deloc. electrons)
Graphene - a single layer of graphite.
71
What are the characteristics of fullerene?
Fullerenes
- hollow shaped molecules
- based on hexagonal rings but may have
5/7-carbon rings
- C6o
• has spherical shape, simple
molecular structure (Buckminsterfullerene)
72
What are the characteristics of graphite?
Graphite
- three covalent bonds for each carbon atom
- layers of hexagonal rings
- high melting point
- layers 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
73
What are the characteristics of Diamond?
Diamond
-four, strong covalent bonds for each carbon atom
- very hard (Strong bonds)
- very high melting point (strong bonds)
- does not conduct (no delocalised electrons)
74
What are the three way atoms can combine?
- Ionic bonds
- Covalent bonds
- Metallic bonds
75
When do ionic bonds take place?
- Takes place when metals and non-metals react by transferring electrons.
- The atoms involved are oppositely charged particles (known as ions) in which electron transfer occurs.
- The opposite charges attract through electrostatic forces.
76
When do covalent bonds occur?
Non-metal atoms share pairs of electrons between each other.
77
When do metallic bonds occur?
This type of bonding occurs in metals and metal alloys (mixtures of metals).
78
What is an ion?
An ion is an electrically charged atom or group of atoms formed by the loss or gain of electrons.
79
What do the loss or gain of electrons lead to?
A full outer shell of electrons
80
What is the electronic structure of ions of elements in group 1,2,6 and 7?
It will be the same as the noble gas - such as helium, neon, and argon.
81
What are negative ions called?
Negative ions are called anions and form when atoms gain electrons, meaning they have more electrons than protons.
82
What are positive ions called?
Positive ions are called cations and form when atoms lose electrons, meaning they have more protons than electrons.
83
Why do all metals lose electrons?
All metals lose electrons to other atoms to become positively charged ions.
84
Why do non-metals gain electrons?
All non-metals gain electrons from other atoms to become negatively charged ions.
85
How can ionic bonds be shown?
Ionic bonds can be represented diagrammatically using dot and cross diagrams.
86
What should electrons in the dot and cross diagram show?
- The electrons from each atom should be represented by using solid dots and crosses.
- If there are more than two atoms, then hollow circles or other symbols / colours may be used to make it clear.
87
What should the large square brackets encompass?
The large square brackets should encompass each atom and the charge should be in superscript and on the right-hand side, outside the brackets.
88
What happens to the electrons in Sodium (Group 1)?
Sodium is a group 1 metal so loses one outer electron to another atom to gain a full outer shell of electrons.
- A positive sodium ion with the charge 1+ is formed, Na+.
89
How do you work out the formula of an ionic compound?
- If it is a dot-and-cross diagram, then just count the number of atoms of each element.
- This is then equal to the empirical formula of the compound.
- If it is a 3D lattice structure, then look for how many ions are in the lattice.
- Write them down and balance the charges to find the formula for the compound.
90
What is the lattice structure made out of?
The lattices formed by ionic compounds consist of a regular arrangement of alternating positive and negative ions in which the ions are tightly packed together.
91
What are the forces between ions like in the lattice structure?
- Strong electrostatic forces of attraction are present between oppositely charged ions, holding the lattice together.
- Electrostatic forces are strong, acting in all directions - they form the basis of ionic bonding.
92
What does the strong electrostatic forces mean for the lattice structure?
Ionic compounds have high melting and boiling points.
93
What is the lattice arrangement of a lattice structure like?
The lattice arrangement exists in three dimensions which allows solid ionic compounds to form regular shapes.
94
How many ions do solid ionic crystals have?
Solid ionic crystals contain huge numbers of ions and so are referred to as giant ionic lattices.
95
How big are ions?
Ions are incredibly small - a single grain of sodium chloride contains trillions of sodium and chloride ions - so models are used to represent the structure of the ionic compound.
96
What does the 3D ball and stick model show?
The 3D ball and stick model shows the arrangement of oppositely charged ions but represents ionic bonds as sticks between ions; in reality an ionic bond is an electrostatic force of attraction that acts in all directions around an ion.
97
What is a limitation of the 3D ball and stick model?
Another limitation of the 3D ball and stick model is that it incorrectly depicts space existing between individual ions whereas the 3D space-filling model is more accurate (there is not much space between separate ions).
98
What do non-metals share with in order to obtain a full outer shell?
Non-metal atoms can share electrons with other non-metal atoms to obtain a full outer shell of electrons.
99
What happens when two atoms share pairs of electrons?
When two atoms share pairs of electrons, they form covalent bonds.
100
What are the covalent bonds between atoms like?
Very strong
101
What is it called when two or more atoms are covalently bonded together, what does this form?
Molecules
102
What do covalently bonded substances consist of?
Covalently bonded substances may consist of small molecules or giant molecules.
103
Weak i__________ forces e______ between i________ molecules
Weak intermolecular forces exist between individual molecules.
104
What are shared electrons called>
Bonding electrons
- they occur in pairs
105
What are electrons on the outer shell which are not involved in covalent bonds are called?
Electrons on the outer shell which are not involved in the covalent bond(s) are called non-bonding electrons.
106
What do simple covalent molecules not do?
- conduct electricity as they do not contain free electrons
107
What can small covalent molecules be represented by?
Dot and cross diagram
108
What are polymers?
Giant covalent structures
109
What are examples of common polymers?
Common polymers include polythene which is used extensively in plastic bags and polyvinyl chloride (PVC) which has many industrial applications, most notably in the production of water pipes.
110
What are examples of giant covalently bonded structures?
- graphite
- diamond
- silicon dioxide
111
What are the advantages of the dot and cross diagram?
- Useful for illustrating the transfer of electrons.
- Indicates from which atom the bonding electrons come from.
112
What are the disadvantages of the dot and cross diagram?
- Fails to illustrate the 3D arrangements of the atoms and electron shells.
- Doesn’t indicate the relative sizes of the atoms.
113
What are the advantages of the ball and stick model?
- Useful for illustrating the arrangement of atoms in 3D space.
- Especially useful for visualizing the shape of a molecule.
114
What are the disadvantages of the ball and stick model?
- Fails at indicating the movement of electrons
- The atoms are placed far apart from each other, which in reality is not the case as the gaps between atoms are much smaller.
115
What are the advantages of 2D Representation of Molecules?
- Displayed formulae are 2D representations and are basically simpler versions of the ball and stick model.
- Adequately indicate what atoms are in a molecule and how they are connected.
116
What are the disadvantages of the 2D Representation of Molecules?
- Fail to illustrate the relative sizes of the atoms and bonds.
- Cannot give you an idea of the shape of a molecule and what it looks like in 3D space.
117
What are individual metal atoms held together by?
Individual metal atoms are held together by strong metallic bonds forming a lattice structure.
118
What type of bonding occurs in metals and metal alloys?
This type of bonding occurs in metals and metal alloys, which are mixtures of metal.
119
What happens within the metal lattice?
Within the metal lattice, the atoms lose their valence electrons and become positively charged metal ions.
120
Where do the valence electrons belong?
- The valence electrons no longer belong to any specific metal atom and are said to be delocalised.
- This means they can move freely between the positive metal ions and act like a “sea of electrons”.
121
What are the three states of matter?
Solids, liquids and gases
122
What does the state of an object depend on?
A substance can usually exist in all three states, dependent on temperature (and pressure).
123
When do state changes occur?
- State changes occur at the melting point (solid to liquid, liquid to solid) and at the boiling point (liquid to gas and gas to liquid).
- Melting and freezing occur at the melting point.
- Boiling and condensing take place at the boiling point.
124
What is the arrangement of a solid?
Regular arrangement
125
What is the arrangement of a liquid?
Randomly arranged
126
What is the arrangement of a gas?
Randomly arranged
127
What is the movement of particles like in a solid?
Vibrate about a fixed position
128
What is the movement of particles like in a liquid?
Move around each other
129
What is the movement of particles like in a gas?
Move quickly in all directions
130
What is the closeness of particles like in a solid?
Very close
131
What is the closeness of particles like in a liquid?
Close
132
What is the closeness of particles like in a gas?
Far apart
133
What does the amount of energy needed to change a state depend on?
- The amount of energy needed to change state from solid to liquid and from liquid to gas depends on the strength of the forces between the particles.
- The stronger the forces of attraction, the more energy that is needed to overcome them for a state change to occur.
134
What is the interconversion of state?
When matter changes from one state to another due to changes in temperature or pressure.
135
Are physical changes easy to reverse?
Physical changes are relatively easy to reverse as no new substance is formed during interconversions of state.
136
What is a physical change involving changes in the forces?
It is a physical change involving changes in the forces between the particles of the substances, the particles themselves remain the same, as do the chemical properties of the substance.
137
What change does melting involve?
Solid to a liquid
138
What change does boiling involve?
Liquid to a gas
139
What change does freezing involve?
Liquid to a solid.
140
What change does evaporation involve?
Liquid to a gas (at surface only)
141
What change does condensation involve?
Gas to a liquid
142
What changes does sublimation involve?
Solid to a gas
143
What type of energy does melting require?
- The process requires heat energy which transforms into kinetic energy, allowing the particles to move.
- It occurs at a specific temperature known as the melting point which is unique to each pure solid.
144
How does boiling take place?
- This requires heat which causes bubbles of gas to form below the surface of a liquid, allowing for liquid particles to escape from the surface and from within the liquid.
- It occurs at a specific temperature known as the boiling point which is unique to each pure liquid.
145
What happens in freezing?
This is the reverse of melting and occurs at exactly the same temperature as melting, hence the melting point and freezing point of a pure substance are the same
Water for example freezes and melts at 0 ºC.
146
What does freezing require?
It requires a significant decrease in temperature (or loss of thermal energy) and occurs at a specific temperature which is unique for each pure substance.
147
What does evaporation involve?
- Evaporation occurs only at the surface of liquids where high energy particles can escape from the liquids surface at low temperatures, below the boiling point of the liquid.
- The larger the surface area and the warmer the liquid/surface, the more quickly a liquid can evaporate.
- Evaporation occurs over a range of temperatures, but heating will speed up the process as particles need energy to escape from the surface.
148
What does condensation involve?
When a gas is cooled its particles lose energy and when they bump into each other, they lack energy to bounce away again, instead grouping together to form a liquid.
149
What does sublimation require?
- This happens to only a few solids, such as iodine or solid carbon dioxide.
- The reverse reaction also happens and is called desublimation or deposition.
150
What does the particle theory explain?
Particle theory explains how matter changes state depending on the energy and forces present between the particles in the substance.
151
What does the amount of energy needed to change from a solid to a liquid depend on?
The relative strength of the forces acting between the particles.
152
Why is the amount of energy needed to induce a change of state different depending on the element and compound?
Since each substance contains different particles, then the amount of energy needed to induce a change of state is different for each individual substance.
153
What does the stronger the forces between the particles mean for the melting and boiling point?
The stronger the forces between the particles, the higher the energy needed for melting and boiling to occur.
154
What happens when substances are heated?
When substances are heated, the particles absorb thermal energy which is converted into kinetic energy.
155
What does heating a solid cause?
Heating a solid causes its particles to vibrate more and as the temperature increases, they vibrate so much that the solid expands until the bonds break and the solid melts.
156
What happens when the boiling point is reached?
When the boiling point is reached, all the particles gain enough energy for the intermolecular forces to break and the molecules to escape as the liquid boils.
157
What happens when a substance changes state?
While changing state, the temperature of the substance remains the same as the heat energy goes into breaking the bonds between the particles = latent heat
158
What are the limitations of the particle theory?
- Particle theory considers all particles, irrespective of their state or chemical identity, to be small, solid and inelastic.
- It doesn’t consider the difference caused by different particles, such as atoms, ions or molecules or mixtures of all three.
- The theory also fails to consider the intermolecular forces that exist between different particles in different substances.
159
What happens to a substance at temperatures below the melting point?
The substance will be in the solid state.
160
What happens to a substance at temperatures between the melting and boiling point?
The substance will be in the liquid state.
161
What happens to a substance at temperatures above the boiling point?
The substance will be in the gas state.
162
What temperature does water boil at?
100 degrees
163
What are the characteristics of a solid?
- Strong forces of attraction between particles, particles are packed very closely together in a fixed and regular pattern.
- Atoms vibrate in a fixed position but can’t change position or move.
- Solids have a fixed volume and shape, and a relatively high density.
- Solid particles have only a small amount of energy.
164
What are the characteristics of liquids?
- There are weaker attractive forces between the particles of a substance in a liquid than in its corresponding solid form.
- Particles are close together in an irregular, unfixed form.
- Particles can move and slide past each other which is why liquids adopt the shape of the container they are in and also why they are able to flow.
- Liquids have a fixed volume but not a fixed shape and have a moderate to high density.
- Liquid particles have more energy than those in a solid but less than gaseous particles.
165
What are the characteristics of gases?
- Particles are in random movement and so there is no defined pattern.
- Particles are far apart and move quickly (around 500 m/s) in all directions, they collide with each other and with the sides of the container (this is how pressure is created inside a can of gas).
- No fixed volume, since there is a lot of space between the particles, gases can be compressed into a much smaller volume. Gases have low density.
- Gaseous particles have the highest amount of energy.
166
What does (s) stand for?
Solid
167
What does (l) stand for?
Liquid
168
What does (g) stand for?
Gas
169
What does (aq) stand for?
Aqueous
170
What are ionic compounds made of?
Ionic compounds are made of charged particles called ions which form a giant lattice structure.
171
What are the characteristics of ionic substances?
Ionic substances have high melting and boiling points due to the presence of strong electrostatic forces acting between the oppositely charged ions.
172
The greater the charge of the ions, means what for the electrostatic forces?
The greater the charge on the ions, the stronger the electrostatic forces and the higher the melting point will be.
173
What are ionic compounds like at room temperature?
- Are usually solid at room temperature and non-volatile.
- They are usually water soluble as both ionic compounds and water are polar substances.
174
What is needed for electrical current to flow?
For electrical current to flow there must be freely moving charged particles such as electrons or ions present .
175
When can ionic compounds conduct electricity?
Ionic compounds can conduct electricity in the molten state or in solution as they have ions that can move and carry charge.
176
When can ionic compounds not conduct electricity?
They cannot conduct electricity in the solid state as the ions are in fixed positions within the lattice and are unable to move.
177
What are small molecules made up of?
Small molecules are compounds made up of molecules that contain just a few atoms covalently bonded together.
178
What are the boiling and melting points of small molecules?
- They have low melting and boiling points.
- Due to the weak intermolecular forces that require little energy
179
What are covalent compounds like in water?
Most covalent compounds are insoluble in water as they tend to be non-polar but can dissolve in organic solvents.
180
What happens to the melting and boiling points as the molecules increase in size?
As the molecules increase in size, the melting and boiling points generally increase.
181
What are small molecules like at conducting electricity?
They are poor conductors of electricity as there are no free ions or electrons to carry the charge..
182
What is the role of most covalent compounds?
Most covalent compounds do not conduct at all in the solid state and are thus insulators.
183
What are common insulators used?
Common insulators include the plastic coating around household electrical wiring, rubber and wood.
184
What is the boiling point of covalent bonds?
- They have low melting and boiling points as there are only weak intermolecular forces acting between the molecules.
- These forces are very weak when compared to the covalent bonds and so most small molecules are either gases or liquids at room temperature.
185
What are polymers?
Polymers are large molecules of high relative molecular mass and are made by linking together large numbers of smaller molecules called monomers.
186
What is each monomer connected to?
Each monomer is a repeat unit and is connected to the adjacent units via strong covalent bonds.
187
What are the intermolecular forces acting in between polymer chains like?
The intermolecular forces acting in between polymer chains are larger than those in between simple molecules so polymers are usually solid at room temperature.
188
What are examples of polymers?
Examples of polymers include polythene and polychloroethene, commonly known as PVC.
189
What are everyday examples of polymers?
- resins
- plastics
- polystyrenes
- nylon
190
What are everyday materials such as resins, plastics, polystyrene, nylon called when manufactured?
Synthetic polymers
191
What polymers does nature produce?
- Natural polymers
- Biological polymers
192
What are examples of natural or biological polymers?
- DNA
- Proteins
- Silk
- Wool
193
What are polymers made from?
Polymers are made from very long carbon chains with a repeating unit.
194
How are polymers drawen?
- Polymers are represented using a specific notation which is shown below using polythene as an example.
- You can spell it polythene or polyethene - both are acceptable.
- The bonds on either side of the polymer must extend outside the brackets (these are called extension or continuation bonds).
- A small subscript n is written on the bottom right hand side to indicate a large number of repeat units.
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What can covalent bonds be responsible for?
Covalent bonding can be responsible for substances that have many different structures and therefore different physical properties.
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What do the simple molecules contain in terms of atoms?
A fixed number
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What are giant covalent structures made up of?
Giant covalent structures on the other hand have a huge number of non-metal atoms bonded to other non-metal atoms via strong covalent bonds.
- These structures can also be called giant lattices and have a fixed ratio of atoms in the overall structure.
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What is the other name for giant covalent structures?
Macromolecules
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Do giant covalent structures have a high melting and boiling point?
They have high melting and boiling points.
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How much energy is needed to overcome giant covalent structures?
These structures can also be called giant lattices and have a fixed ratio of atoms in the overall structure.
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Can giant covalent structures conduct electricity?
Most cannot conduct electricity as they do not have free electrons nor charged particles but there are some exceptions such as graphite and graphene.
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What are examples of giant covalent structures made from Carbon?
Diamond, graphite, buckminsterfuller and graphene are all made from carbon.
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What is the melting and boiling point like for diamond?
Very high
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What is the melting and boiling point like for graphite?
Very high
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What is the melting and boiling point like for Buckminster-fullerene?
Low
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What is the melting and boiling point like for Graphene?
Very high
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What is the melting and boiling point like for silicon dioxide?
Very high
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Is diamond a good electrical conductor?
Non-conductor
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Is graphite a good electrical conductor?
Good
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Is Buckminster-fullerene a good electrical conductor?
Semi-conductor
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Is graphene a good electrical conductor?
Very good conductor
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Is silicon dioxide a good electrical conductor?
Non - conductor
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What is the appearance of diamond like?
Transparent crystals
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What is the appearance of graphite like?
Grey-black solid
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What is the appearance of buckmister-fullerene like?
Yellow solid
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What is the appearance of graphene like?
Transparent sheets
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What is the appearance of silicon dioxide like?
Transparent crystals
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What are the special characteristics of diamond?
Hardest known naturally occuring substance
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What are the special characteristics of graphite?
Soft and slippery
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What are the special characteristics of Buckminster-fullerene?
Very light and strong
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What are the special characteristics of graphene?
Very strong and flexible; 100 times stronger than steel.
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What are the special characteristics of silicon dioxide?
Piezoelectric - produces electric change from mechanical stress
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What are metallic bonds?
Metallic bonds are very strong and are a result of the attraction between the positive metal ions and the negative delocalised electrons within the metal lattice structure.
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What is the melting and boiling point for metals?
Metals thus have very high melting and boiling points and are solids at room temperature, with the exception of mercury which is a liquid.
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What are the qualities of metal?
They are usually insoluble in water although some do react with it.
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What are metals good qualities?
Metals are good conductors of heat and electricity due to the delocalised electrons.
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What can layers of atoms in metals do?
The layers of atoms in metals can slide over each other meaning metals are malleable and can be hammered and bent into shapes or rolled into flat sheets.
